4.4 design flood discharge - jica · 2014. 7. 8. · river, design flood discharge of these...

The Republic of the Philippines Data Collection Survey on Flood Management in Metro Manila

Final Report 4-30

4.4 Design Flood Discharge

With examining the alternatives of flood management facility plan, optimal design flood discharge allocation and its flood management plan is proposed.

Since flood control works for 1/30 years flood have been conducted in Pasig and Lower Marikina River, design flood discharge of these sections shall be set considering the previous works.

Design flood water levels will be checked with the design water level of the JICA Study.

4.4.1 Evaluation of Conditions for Pasig-Marikina River Channel Improvement Project (PMRCIP)

(1) Design Flood Discharge for PMRCIP

PMRCIP can be divided as the following 4 phases.

Phase I : Detailed Design Works for Whole Section

Phase II : River Improvement Works from River Mouth to Confluence of Napindan Channel

Phase III : River Improvement Works from Confluence of Napindan Channel to Diversion of Manggahan Floodway without MCGS

Phase IV : River Improvement Works from Diversion of Manggahan Floodway to Marikina Bridge with MCGS

In the detailed design conducted in 2002, the design flood discharge allocation of 1/30 years flood was formulated as shown in Figure 4.29, and river improvement works and construction of MCGS was planned.

Source: Preparatory Study for Pasig-Marikina Channel Improvement Project (Phase III)

Figure 4.27 H-Q Curve Formulated in JICA M/P Study

(2) Operation of NHCS The JICA Study planned that NHCS should be closed during flood to block inflow from Laguna Lake to Pasig River while the WB Study planned that NHCS should be open during flood to expect reverse flow from Pasig River to Laguna Lake.

Advantages and disadvantages of operation of NHCS are summarized in Table 4.15. With the following reasons, it is judged as appropriate that NHCS shall be closed during flood to avoid uncertain phenomena in flood management plan.


Final Report 4-31

Diversion through Napindan Channel to Laguna Lake is uncertain since reverse flow will happen depending on water level in Laguna Lake.

If NHCS would open during flood, channel improvement of Napindan Channel is inevitable to protect surrounding dense urbanized area resulting difficulty of land acquisitions.

Table 4.15 Comparison of NHCS Operation

Open during Flood Close during Flood

Advantage Gate operation is not required. Inflow from Laguna Lake to Pasig River can be prevented.

Disadvantage

In case WL of Laguna Lake is higher than Pasig River, flood risk in the center of Metro Manila increases due to inflow from Laguna Lake to Pasig River.

Diversion of flood discharge to Laguna Lake through Napindan Channel is uncertain depending of water levels of Laguna Lake and Pasig River.

If diversion to Laguna Lake through Napindan Channel is included in the discharge allocation plan, discharge of Lower Marikina becomes large resulting increase of flood risk and heightening of dyke is required.

Napindan Channel also requires improvement works such as dyke heightening.

Gate operation is required.

Evaluation Not Favorable Favorable Source: JICA Study Team

(3) Necessity of MCGS The JICA Study planned to fully utilize Laguna Lake with sure diversion through Manggahan Floodway controlled by MCGS. On the other hand, the WB Study recommended that MCGS is not necessary and flood control is planned with diversion through Napindan Channel. Advantages and disadvantages of MCGS are summarized in Table 4.16.

MCGS is necessary for sure diversion of design discharge to Laguna Lake. Besides, excess flood also can be diverted to Manggahan Floodway by MCGS resulting mitigation of flood risk at the center of Metro Manila.

Without MCGS, re-improvement of channel downstream of Rosario Weir since HWL increases. Rise of HWL leads to increase of flood disaster potentials.

Table 4.16 Comparison of With/Without MCGS

Without MCGS With MCGS

Advantage WL of Upper Marikina decrease.

Sure diversion is available. Excess flood also can be diverted resulting

mitigation of flood risk at the center of Metro Manila.

Disadvantage

Flood risk for excess flood increase. HWL in Pasig-Lower Marikina increases

leading to increase of flood disaster potentials

Gate operation is required. WL in Upper Marikina rise.

Evaluation Not Favorable Favorable Source: JICA Study Team

The basic specifications and operation rule of MCGS designed in the detailed design in 2002 are summarized in Table 4.17.


Final Report 4-32

Table 4.17 Comparison of With/Without MCGS Item Specifications

Design Discharge 500m3/s (Lower Marikina River) Design HWL Upstream Side: EL. 17.40m

Downstream Side: EL. 14.74m Design Section Riverbed Width: 43.5m

Riverbed Elevation: EL.8.0ｍ Gate Dimensions: W20ｍ x H11ｍ x 2 units

Type: Roller Gate Operation Rule MCGS Gate shall be operated together with Rosario Weir with monitoring of levels of Manila

Bay, Laguna Lake and Sto.Nino for secure diversion of design discharge. Source: JICA Study Team

Discharge allocations to Manggahan Floodway and Lower Marikina, and influence to downstream with/without MCGS is simulated with following conditions. Diversion volumes of the both case, 1/20 years flood discharge allocation, and longitudinal flow profile of it are summarized in Table 4.18, Figure 4.30 and 4.31, respectively.

Design discharge at Sto.Nino is 2,900 m3/s which equivalent to 1/20 years flood with natural retarding function is applied.

NHCS is closed not to divert to Laguna Lake through Napindan Channel.

Manggahan Floodway has designed capacity without illegal residents in the river course.

Without MCGS, the following disadvantage occurs.

Design diversion discharge to Manggahan Floodway of 2,400 m3/s is not secured.

Water levels in Pasig-Lower Marikina River rise higher than the design HWL about 1 m as maximum resulting increase of flood risk. RE-improvement such as heightening of dyke is required.

Table 4.18 Diversion Discharge With/Without MCGS

Marikina (Before Diversion)

Lower Marikina (After Marikina) Manggahan Floodway

Without MCGS 2,900 m3/s 1,000 m3/s 1,900 m3/s With MCGS 2,900 m3/s 500 m3/s 2,400 m3/s

Source: JICA Study Team

2,900

2,900

1,600 1,000 1,000 1,000

0 1,900

650

Laguna Lake

Ma

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F

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Na

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Ch

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ari

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Sto.Nino

Pasig River

Sa

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NHCS

Rosario Weir

PPManila Bay

2,900

2,900

1,200 600 500 500

0 2,400

650

Laguna Lake

Ma

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Na

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Marikina River (Lower)Pasig River M

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Sto.Nino

Pasig River

Sa

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uan

Riv

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MCGS

NHCS

Rosario Weir

PPManila Bay


Figure 4.28 Discharge Allocation With/Without MCGS (1/20 years, with Natural Retarding Function)

Without MCGS With MCGS

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Final Report 4-34

(4) Consideration of Urban Development along Marikina River

At near Rosario Weir, urban development program is on-going by private developers as shown in Figure 4.32. Influence of this development is calculated based on the design drawings of development program. As shown in Figure 4.33, rise of water level due to the urban development is just 20 cm which can be adjusted in the Phase IV Project.

Figure 4.30 H-Q Curve Formulated in WB Study


Figure 4.31 Flow Profile of Influence of Urban Development Program

(5) Evaluation of Probability of Design Flood Discharge by PMRCIP Based on the review of hydrological analysis referring the observed flood in recent years, probable flood discharge of 1/30 years return period is estimated at 3,100 m3/s which is 200 m3/s larger than the design discharge of 2,900 m3/s. Table 4.19 shows the probable discharges at Sto.Nino with natural retarding function. According to Table 4.19, the design flood discharge of PMRCIP of 2,900 m3/s is reevaluated as 1/20 years flood.

Table 4.19 Reviewed Probable Discharge at Sto.Nino

Return Period Sto.Nino (With Inundation) Return Period Sto.Nino (With Inundation) 2 1,620 30 3,030 5 2,290 50 3,220

10 2,670 100 3,580 20 2,860



Final Report 4-35

4.4.2 Flood Management Plan for 1/30 Years Flood

(1) Conditions for Examination The following conditions were applied to examine the flood management plan for 1/30 years flood.

Change of HWL at the section where PMRCIP has been conducted or on-going since the social infrastructures have been developed based on the designed HWL. Therefore, HWL at the section where PMRCIP has conducted including Phase III Section shall remain same. For Phase IV Section, minor change is considered acceptable.

Diversion through Napindan Channel to Laguna Lake is uncertain since reverse flow will happen depending on water level in Laguna Lake. As discussed in Section 4.4.1, NHCS is closed during flood and inflow from Pasig River to Laguna Lake through Napindan Channel is not considered.

MCGS is to be constructed.

Flood management plan is examined for 1/30 years flood with natural retarding function as shown in Figure 4.34.

3,100

3,100

1,300 600 500 500

0 2,600

700

Laguna Lake

Mang

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Flo

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Marikina River (Lower)Pasig River

Nangka River

Marik

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Sto.Nino

Pasig River

San Ju

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MCGS

NHCS

Rosario Weir

Montalban

PP

Natural Retarding Basin


Figure 4.32 Discharge Allocation of 1/30 Years Flood

(2) Alternatives of Flood Management Plan for 1/30 Flood Since the discharge allocation downstream of MCGS is already fixed, flood management plan can be considered upstream of MCGS such as following 2 alternatives.

A: To retain flood discharge in Laguna Lake through Manggahan Floodway.

B: To retain flood discharge at retarding basin upstream of Sto.Nino.

Thus the following 2 alternatives for countermeasure are examined adding to the Phase IV components consisting channel improvement from MCGS to Marikina Bridge and construction of MCGS.

Alternative-a: Phase IV with Dyke Heightening + Improvement of Manggahan Floodway

Alternative-b: Phase IV without Dyke Heightening + Construction of Retarding Basin


Final Report 4-36

(3) Alternative-a: Phase IV with Dyke Heightening + Improvement of Manggahan Floodway

1) Discharge Allocation 3,100 m3/s between Risario Weir to Sto.Nino with Channel Improvement

2,600 m3/s to Manggahan Floodway and 500 m3/s to Lower Marikina River

2) Improvement Plan In Upper Marikina River, heightening of dyke such as parapet is required since HWL rise about

50 cm of the flow sections designed in the detailed design in 2002.

Since required discharge of Manggahan Floodway is 2,600 m3/s which is 200 m3/s larger than design discharge of 2,400 m3/s, improvement works is required.


Figure 4.33 Alternative-a: Phase IV with Dyke Heightening + Improvement of Manggahan Floodway (1/30 Years)


Final Report 4-37

(4) Alternative-b: Phase IV without Dyke Heightening + Construction of Retarding Basin

1) Discharge Allocation 2,900 m3/s between Risario Weir to Sto.Nino with control of 200 m3/s at the retarding basins

upstream of Sto.Nino.

2,400 m3/s to Manggahan Floodway and 500 m3/s to Lower Marikina River

2) Improvement Plan In Upper Marikina River, flow sections designed in the detailed design in 2002 can be remained.

Required discharge of Manggahan Floodway is 2,400 m3/s, same as design discharge. To recover the designed flow capacity, dredging works and relocation of illegal residents are required.

Increase of capacity of retarding basin up to 35 MCM is required by excavation of natural retarding basin where current capacity is 5 MCM.

Source: JICA Study Team Figure 4.34 Alternative-b: Phase IV without Dyke Heightening + Construction of Retarding

Basin (1/30 Years)

3) Scale of Retarding Basin

a) Retarding Basin Development In case the retarding basin development scenario is taken for 1/100 years flood management measures, the necessary capacities of retarding basin to reduce discharge at Sto.Nito to 3,100m3/s and 2,900m3/s are 20MCM and 25MCM, respectively. (refer to Table 4.20 and Figure 4.35)


Final Report 4-38

Table 4.20 Control Volume of Retarding Basin for 1/30 Flood

Return Period Number of FCB(Locations）

Area （ha）

Volume (1,000m3）

Average Excavation Depth（m）

Natural drainage

Before Control (m3/s）

After Control (m3/s）

Effect (m3/s）

30 8 371 20,007 4.0 Yes 3,970 3,100 870

30 8 371 25,296 7.5 No 3,970 2,890 1,080


Source: JICA Study Team Figure 4.35 Hydrograph at Sto.Nino before and after Control by Retarding Basin

b) Enhancement of Natural Retarding Basin Necessary volume of retarding basin is estimated at 5 MCM to control discharge at Sto.Nino to 2,900 m3/s from 3,100 m3/s by cutting 200 m3/s of 1/30 years flood. Total retaining volume will be 35 MCM with current natural retarding function of 30 MCM.

Area and location of natural retarding basin is assumed as inundation area by 1/30 years flood by simulation as shown in Figure 4.36. The area is about 1,000ha and its capacity is about 30 MCM.


Final Report 4-39


Figure 4.36 Location of Natural Retarding Basin (Estimated Inundation Area of 1/30 years Flood)

Inundation Area ：949ha Inundation Volume ：30.3MCM


Final Report 4-40

(5) Evaluation of Alternatives

The 2 alternatives shown in Table 4.21 are compared as summarized in Table 4.22. Their discharge allocations and flow profiles are shown in Figure 4.38 to 4.40. Both alternatives is feasible, however, if land acquisition for retarding basin is difficult, Alternative-a is recommended since it can be implemented in the Phase IV Project.

Table 4.21 Summary of Alternatives for 1/30 Years Flood Management

Alternative Pasig NHCS Lower Marikina MCGS Mangahan Floodway Upper Marikina Upper-Upper

Marikina

a Existing Condition Close

River Improvement (PhaseⅢ)

With Excavation &

Widening Q=2,600m3/s

River Improvement (DD 2002) With CV*

Existing Condition +Natural Retarding Basin

b Existing Condition Close

River Improvement (PhaseⅢ)

With Excavation(removal of sedimentation)

Q=2,400m3/s

River Improvement (DD 2002) With CV*

Existing Condition +Natural Retarding Basin+Additional Capacity 5MCM

CV:Circulo Verde Development Plan

Upper Marikina River Improvement(DD 2002) ; Q2,900m3/s Source: JICA Study Team

3,100

3,100

1,300 600 500 500

0 2,600

700

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Mang

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Flo

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Napin

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Chan

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Nangka River

Marik

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Pasig River

San Ju

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MCGS

NHCS

Rosario Weir

MontalbanAlternative-02Return Period: 30-yearNatural Retarding Basin: withNHCS: CloseMCGS: With

PP

Natural Retarding Basin

2,900

2,900

1,300 600 500 500

0 2,400

700

Laguna Lake

Mang

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Flo

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Napin

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Chan

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Nangka River

Marik

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Sto.Nino

Pasig River

San Ju

an Ri

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MCGS

NHCS

Rosario Weir

MontalbanAlternative-03Return Period: 30-yearNatural Retarding Basin +Flood Control Basin:NHCS: Close

PP

Natural Retarding Basin+Additonal CapacityV=5MCM


Figure 4.37 Alternatives of Design Flood Discharge Allocation for 1/30 Years Flood

Alternative-a

Alternative-b


Final Report 4-41

Table 4.22 Comparison of Alternatives for 1/30 Years Flood Management Alternative-a:

Channel Improvement of Marikina River + MCGS + Improvement of Manggahan

Floodway

Alternative-b: Channel Improvement of Marikina River +

MCGS + Retarding Basin

Structures Channel Improvement of Marikina River (PhaseⅡ&Ⅲ&Ⅳ)

MCGS

Channel Improvement of Marikina River (PhaseⅡ&Ⅲ&Ⅳ)

MCGS Discharge Allocation

3,100 m3/s at Rosario Weir is diverted to Main River with 500 m3/s and to Manggahan Floodway with 2,600 m3/s.

3,100 m3/s discharge is reduced to 2,900 m3/s at Sto.Nino by retarding basin. 2,900 m3/s at Rosario Weir is diverted to Main River with 500 m3/s and to Manggahan Floodway with 2,400 m3/s.

Water Level

Less than HWL in Pasig River. Less than HWL in Lower Marikina River. Excess HWL with 0.1 m to 0.5 m in Upper Marikina River.

Less than HWL in Pasig River. Less than HWL in Lower Marikina River. Excess HWL with 0.1 m to 0.5 m in Upper Marikina River due to Urban Development Project.

Measures for Excess Flood

Excess flood can be diverted to Laguna Lake by MCGS.

Excess flood can be diverted to Laguna Lake by MCGS.

Necessity of Additional Works

There is no re-improvement in PhaseII and III sections. Heightening of Phase IV section is required. Improvement of Manggahan Floodway is required.

There is no re-improvement in Phase II, III and IV sections. Construction of retarding basin upstream of Sto.Nino is required after Phase IV.

Evaluation Social impact is less since there is no change of HWL in Phase II and III sections. Heightening of Phase IV section is available. Discharge of excess flood to the center of Metro Manila can be controlled.

Good

Social impact is less since there is no change of HWL in Phase II, III and IV sections. Construction of retarding basin should be after Phase IV Project. Land acquisition for retarding basin is required. Discharge of excess flood to the center of Metro Manila can be controlled.

Fair Source: JICA Study Team

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Final Report 4-44

(6) Scale of Manggahan Floodway Improvement

1) Current Conditions Manggahan Flood way was completed in 1988 with the design discharge of 2,400m3/s. However, flow area has been reduced mainly due to houses in river course and sedimentation. If design discharge of 2,400m3/s flows into the channel, water level rise about 1.2m higher than design HWL, which is higher than current dyke level in the section from 1.5 to 3.0 km from Rosario Weir.

Figure 4.40 Current Conditions of Manggahan Floodway

Figure 4.41 Longitudinal Flow Profile (Current and after Excavation, Q=2,400m3/s)

2) Restoration to 2,400m3/s

This alternative is to restore capacity of Manggahan Floodway to the original design capacity of 2,400m3/s by resettlement of houses in river course and dredging works to the design riverbed level. Water level of the floodway with Q=2,400m3/s is confirmed by non-uniform flow calculation. Typical section and longitudinal flow profile are shown in Figure 4.44 and 4.45, respectively.

Lower End Start W.L.: Laguna Lake W.L. 13.9m River Section: Current condition (with Houses, n=0.300)

After dredging condition (n=0.030) Calculation Case: Design discharge 2400m3/s


Final Report 4-45

Figure 4.42 Typical Section after Dredging Works

Figure 4.43 Longitudinal Flow Profile (After Excavation, Q=2,400m3/s)

3) Improvement to 2,600m3/s Water level increases about 30cm at Rosario Weir if discharge of 2,600m3/s flows into Manggahan Floodway. To reduce the water level to same as 2,400m3/s discharge, widening of river course is required as show in Figure 4.46. Longitudinal flow profile is shown in Figure 4.47.

Current Condition

After Dredging

Lower End Start W.L.: Laguna Lake W.L. 13.9m River Section: After dredging condition (n=0.030) Calculation Case: Design discharge 2400m3/s


Final Report 4-46

Figure 4.44 Typical Section after Widening

Figure 4.45 Longitudinal Flow Profile

(After Excavation Q=2,400m3/s, With Widening Q=2,600m3/s)

0.5m 1：2.0

150m 1：2.0 1：2.0

Current Condition

After Dredging After Improvement

After Improvement

Current Condition

After Dredging

Lower End Start W.L.: Laguna Lake W.L. 13.9m River Section: After dredging condition (n=0.030)

After improvement condition (n=0.030) Calculation Case: After dredging Q=2400m3/s

After improvement Q=2600m3/s


Final Report 4-47

(7) Lower Reach of MCGS

1) 1/30 Years Flood Allocation

River channel improvement in San Juan River is planned of which design discharge at confluence is 780m3/s with 1/100 years flood while 1/30 years flood discharge is 670m3/s. Since the applied hyetograph is different, peak discharge after the confluence is becomes 1,300m3/s which is 100 m3/s larger than the design discharge in the detailed design in 2002 as shown in Figure 4.48 and 4.49.

Figure 4.46 1/30 Years Flood Allocation in Pasig River

Figure 4.47 Hydrograph of 1/30 Years Flood at Confluence of San Juan River

2) 1/30 Years Flood Measure To flow the increased design discharge of 1,300m3/s, dredging of lower Pasig Reach from 0.0k to 2.0k to the design riverbed level in 1990 Master Plan. Longitudinal Flow Profile is shown in Figure 4.50.

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Final Report 4-49

4.4.3 Flood Control Measures for 1/100 Years Flood

(1) Possible Measures for 1/100 Years Flood

As measures to be implemented after the Phase IV completed, flood control effects of possible 1/100 flood control facilities at upstream of Sto.Nino. Possible flood control facility is as follows.

Dam

Retarding Basin

Dam + Retarding Basin

Source: JICA Study Team Figure 4.49 Possible Flood Control Facilities Upstream of Sto.Nino for 1/100 Years Flood

(2) Flood Control Effect of Dam

For examination of effect of dam, 4 cases of reservoir capacities with 55 MCM, 65 MCM, 80 MCM and 90 MCM are examined. H-V curve is estimated based on the reservoir volumes by elevation which estimated by the WB Study since it was not examined in the JICA M/P Study. H-V curve is estimated by 1 m interval of elevation by spline interpolation. H-V relation and curve are shown in Table 4.23 and Figure 4.42, respectively.

Table 4.23 H-V Relation of Proposed Dam

Elevation(m) Volume(MCM) 55 0 60 2.325 80 32.325

100 89.025 120 181.53 140 320.63

Source: Master Plan for Flood Management in Metro Manila and Surrounding Areas, the World Bank


Final Report 4-50


Figure 4.50 H-V Curve of Proposed Dam

1) Conditions for Estimation of Flood Control Effect of Dam Flood control effect of dam is estimated based on the following conditions.

In the WB Study, sedimentation volume varies depending on dam height because it is estimated as 10% of total reservoir capacity. However, since sedimentation does not related to dam height, fixed dead volume is applied same as the JICA M/P Study.

Considering the safety factor, flood control capacity is set as 1.2 times of calculated flood control capacity

Peak outflow discharge is set considering flow capacity of downstream.

Basic specifications of dams are summarized in Table 4.24.

Table 4.24 Specifications of Dams Examined

Case H (m) E L top (m)

LWL (m)

SWL (m)

V total (1,000m3)

V effective (1,000m3)

V dead (1,000m3) Orifice

55MCM 68 98 67 93 63,551 54,398 9,153 5.7×5.7×3unit

65MCM 71 101 67 96 73,684 64,531 9,153 4.3×4.3×3unit

80MCM 75 105 67 100 86,342 77,189 9,153 3.1×3.1×3unit

90MCM 77 107 67 102 96,316 87,163 9,153 3.1×3.1×3unit Source: JICA Study Team

2) Estimation Results Flood control effect of dam is estimated as summarized in Table 4.25 and Figure 4.43 to 4.45. It is noted that hydrographs at Montalban and Sto.Nino does not consider inundation upstream.


Final Report 4-51

Table 4.25 Specifications of Dams Examined

Case Dam

Montalban (m3/s) Sto.Nino (m3/s) Peak Inflow (m3/s) Peak Outflow (m3/s)

55MCM

3,230

1,820 2,840 3,790 65MCM 1,450 2,500 3,470 80MCM 1,050 2,140 3,100 90MCM 710 1,900 2,900



Figure 4.51 Hydrographs at Dam Location


Figure 4.52 Hydrographs at Montalban


Final Report 4-52


Figure 4.53 Hydrographs at Sto.Nino

(3) Flood Control Effect of Retarding Basin

1) Conditons for Estimation of Flood Control Effect of Retarding Basin Specifications of retarding basins are determined with the following conditions.

Candidate areas are selected based on the inundation area of 2009 Flood and un-urbanized area as of 2011. Bed elevation of retarding basin is determined as the level which allows natural drain to river. HWL of retarding basin is determined as same as HWL of Marikina River at drainage outlet position. HWL of Mrikina River is same as the design high water level.

Length of overflow dyke is determined to maximize capacity of retarding basin.

Specifications and locations of candidate retarding basins are shown in Table 4.26 and Figure 4.47.

Table 4.26 Specifications of Candidate Retarding Basin

NO. Area （ha）

HWL （EL.m）

Bed Elevation (EL.m)

Depth （m）

Capacity* （1,000m3）

1 85 26.254 22.254 4.0 4,870 2 114 26.142 22.142 4.0 6,195 3 82 24.877 20.877 4.0 4,267 4 8 24.749 20.749 4.0 397 5 36 23.880 19.880 4.0 1,901 6 21 21.761 17.761 4.0 1,137 7 16 21.229 17.229 4.0 835 8 8 21.637 17.637 4.0 405

Total 371 20,007 Remarks: Capacity is 1.2 times of calculated capacity considering safety factor. Source: JICA Study Team


Final Report 4-53


Figure 4.54 Locations of Candidate Retarding Basin


Final Report 4-54

2) Estimation Results

The results of estimation of the maximum flood control effect of retarding basins against 1/100 years flood is shown in Table 4.26 and Figure 4.46. Effect is only 740 m3/s as evaluated as discharge at Sto.Nino.

Table 4.27 Flood Control Effect of Retarding Basin

Return Period Dam Size Number of

FCB(Locations） Area （ha）

Volume (1,000m3）


Natural drainage



Effect (m3/s）

100 Without Dam (FCB Only） 8 371 20,004 4 Yes 4,973 4,232 741



Figure 4.55 Hydrograph of Retarding Basin Effect at Sto.Nino (1/100 Flood) (4) Flood Control Effect of Dam + Retarding Basin

1) Conditons for Estimation of Flood Control Effect of Retarding Basin

The following cases are examined as the combination of dam and retarding basin.

Table 4.28 Estimation Cases of Dam + Retarding Basin

Case Composition Case 1 Dam (55MCM) + Retarding Basin (Max, Natural Drain) Case 2 Dam (65MCM) + Retarding Basin (Max, Natural Drain)


2) Estimation Results The results of estimation of the maximum flood control effect of retarding basins against 1/100 years flood is shown in Table 4.29 and Figure 4.48.

Table 4.29 Flood Control Effect of Dam + Retarding Basin

Case Dam Size Number of FCB(Locations）

Area （ha）

Volume (1,000m3）


Natural drainage



Effect (m3/s）

Case1 55MCM 8 371 20,004 4 Yes 3,790 3,090 700

Case2 65MCM 8 371 20,004 4 Yes 3,470 2,850 620


Final Report 4-55



Figure 4.56 Hydrographs of Dam + Retarding Basin Effect at Sto.Nino

(5) Lower Reach of MCGS

1) 1/100 Years Flood Allocation

1/100 years flood allocation in lower reach of MCGS is as shown in Figure 4.59 and 1/100 years flood discharge at river mouth becomes 1,400m3/s assuming channel improvement of San Juan River with design discharge of 780m3/s is completed. It is 200m3/s higher than the design discharge in the detailed design in 2002.

Case 1

Case 2


Final Report 4-56

Figure 4.57 1/100 Years Flood Allocation in Pasig River and Hydrograph at Confluence of San

Juan River

2) 1/100 Years Flood Measure

To flow the increased design discharge of 1,400m3/s, dredging of lower Pasig Reach from 0.0k to 5.6k to the design riverbed level in 1990 Master Plan. Longitudinal Flow Profile is shown in Figure 4.50.

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

57

So

urce

: JIC

A St

udy

Team

Fi

gure

4.5

8 Lo

ngitu

dina

l Flo

w P

rofil

e of

Pas

ig-L

ower

Mar

ikin

a (Q

=1,4

00m

3 /s)


Final Report 4-58

4.4.4 Flood Management Plan for 1/100 Years Flood Flood management plan for 1/100 years is examined considering development scenario of flood management measures. (1) Urgent Flood Management Measures

As the urgent flood management measures until the completion of Phase IV Project, the following 3 alternatives are considerable.

Alt-O: 1/30 years flood (as of 2002) measures by Phase IV component (Q=2,900m3/s at Sto.Nino)

Alt-A: 1/30 years flood measures by Phase IV components with improvement of Manggahan Floodway (Q=3,100m3/s at Sto.Nino)

Alt-B: 1/30 years flood measures by Phase IV components with improvement of retarding basin in upper-upper Marikina (Q=2,900m3/s at Sto.Nino)

Out of 3 alternatives, 2 alternatives to improve up to 1/30 years flood measures are recommended because additional measures can be included in Phase IV Project.

Table 4.30 Alternatives for Urgent Flood Management Measures


(2) Development Scenario to 1/100 Years Flood Management

Alternatives of the phased development scenario to 1/100 years flood management are shown in Figure 4.50. After the Phase IV Project completed, safety degree can be improved by construction of dam or dam + retarding basin.

As for retarding basin development, the following 3 patterns shown in Figure 4.49 are possible. It shall be determined in detailed design stage.


Final Report 4-59


Figure 4.59 Pattern of Retarding Basin Development

■Natural Retarding Basin

■Enhancement of Retarding Function (as of mid-stage of development)

■Retarding Basin Development

“Natural Retarding Basin” is to maintain current natural retarding function of basin. Some urbanized area will be included in the retarding basin.

“Retarding Basin Development” is to develop about 400 ha out of 1,000 ha natural retarding basin.

“Enhancement of Retarding Function” is to excavate whole or parts of 400 ha to improve retarding functions.

Current natural retarding basin is 1,000 ha with capacity of 30 MCM. Out of it, urbanized area is 60% with capacity of 18 MCM, and candidate retarding basin has area of 400 ha with capacity of 12 MCM.

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

60

So

urce

: JIC

A St

udy

Team

Figu

re 4

.60

Alte

rnat

ives

of P

hase

d D

evel

opm

ent S

cena

rio


Final Report 4-61



Figure 4.61 Images of Development Scenario(A-1 to A-3)

A-1: Dam + Natural Retarding Basin

Step1: 1/30 years

Step2: 1/100 years (Dam Completed)

A-2-1: Dam

Step1: 1/30 years


A-3: Dam + Retarding Basin

Step1: 1/30 years

Step2: 1/30＋α (Enhance of Retarding Function)

Step3: 1/100 years (Dam + Retarding Basin)

A-2-2: Dam + Temporary Retarding Basin

Step1: 1/30 years

Step2: 1/30＋α(Enhance of Retarding Function)



Final Report 4-62


Figure 4.62 Images of Development Scenario(B-1 to B-4)

O-1: Dam + Natural Retarding Basin

Step1: 1/30 yeras (as of 2002)


O-2: Dam

Step1: 1/30 years (as of 2002)


B-1: Dam + Enhancement of Retarding Function

Step1: 1/30 (Enhance of Retarding Function)


B-2-1: Dam



B-3: Dam + Retarding Basin Development


Step2: 1/30 + α (Enhance of Retarding

Function)

Step3: 1/100 (Dam + Retarding Basin)

B-2-2: Dam Step1: 1/30 (Enhance of Retarding Function)

Step2: 1/30＋α(Enhance of Retarding Function)



Final Report 4-63

(3) Alternatives of 1/100 Years Flood Management Plan with Phase IV + Manggahan Floodway as 1/30 Years Measure

There are 4 alternatives can be applied if Phase IV + Manggahan Floodway is applied as 1/30 years flood management measures.

Alt A-1: Dam + Natural Retarding Basin

Alt A-2-1: Dam Only

Alt A-3: Dam + Retarding Basin Construction

Alt A-2-2: Dam + Temporary Retarding Basin (after dam completed, retarding basin will be demolished and land use changed.)

(4) Alternatives of 1/100 Years Flood Management Plan with Phase IV + Retarding Basin as 1/30 Years Measure

There are 6 alternatives can be applied if Phase IV + Retarding Basin is applied as 1/30 years flood management measures.

Alt O-1: Dam + Natural Retarding Basin

Alt O-2: Dam Only

Alt B-1: Dam + Natural Retarding Basin + Excavation of Retarding Basin

Alt B-2-1: Dam + Temporary Retarding Basin (after dam completed, retarding basin will be demolished and land use changed.)

Alt B-3: Dam + Retarding Basin Construction

Alt B-2-2: Dam + Temporary Retarding Basin (after dam completed, retarding basin will be demolished and land use changed.)

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

64

Tabl

e 4.

31

Alte

rnat

ives

for

Urg

ent F

lood

Man

agem

ent M

easu

res (

Sto.

Nin

o: 3

,100

m3 /s)

Fl

ood

Man

agem

ent

Mea

sure

s fo

r 1/1

00 Y

ears

Floo

dAl

tern

ativ

e-A-

1Al

tern

ativ

e-A-

2-1

Alte

rnat

ive-

A-3

Alte

rnat

ive-

A-2-

2

Disc

harg

e Al

loca

tion

Uppe

r Upp

er M

arik

ina

Rive

rD

am +

Nat

ural

Ret

ardi

ng B

asin

Dam

: 55

MCM

, Nat

ural

Ret

ardi

ng B

asin

: 30

MCM

Cha

nnel

Impr

ovem

ent

+ D

amDa

m: 8

0MCM

Cha

nnel

Impr

ovem

ent

+ D

am +

Ret

ardi

ngB

asin

Dam

: 55M

CM　

Reta

rdin

g Ba

sin:

20M

CM

Cha

nnel

Impr

ovem

ent

+ D

am (

+E

nhan

cem

ent

of R

etar

ding

Fun

ctio

n)Da

m: 8

0MCM

Uppe

r Mar

ikin

a Ri

ver

Phas

e IV

Com

pone

nts

+ He

igth

ning

to3,

100m

3/s

Phas

e IV

Com

pone

nts

+ He

igth

ning

to3,

100m

3/s

Phas

e IV

Com

pone

nts

+ He

igth

ning

to3,

100m

3/s

Phas

e IV

Com

pone

nts

+ He

igth

ning

to3,

100m

3/s

Man

gaha

nDr

edgi

ng to

2,6

00m

3/s

Dred

ging

to 2

,600

m3/

sDr

edgi

ng to

2,6

00m

3/s

Dred

ging

to 2

,600

m3/

s

Lowe

r Mar

ikin

a Ri

ver

Curre

nt P

hase

III C

ompo

nent

sCu

rrent

Pha

se II

I Com

pone

nts

Curre

nt P

hase

III C

ompo

nent

sCu

rrent

Pha

se II

I Com

pone

nts

Pasi

g Ri

ver

Phas

e II

+ Dr

edgi

ng to

1,4

00m

3/s

Phas

e II

+ Dr

edgi

ng to

1,4

00m

3/s

Phas

e II

+ Dr

edgi

ng to

1,4

00m

3/s

Phas

e II

+ Dr

edgi

ng to

1,4

00m

3/s

61,8

13.7

65,6

10.6

66,2

76.1

69,4

92.5

(1.0

00)

(1.0

61)

(1.0

72)

(1.1

24)

Adva

ntag

esSc

ale

of D

am c

an b

e m

inim

ize

by u

tiliz

atio

n of

natu

ral r

etar

ding

bas

in.

Land

use

of re

tard

ing

basi

n is

ava

ilabl

e.

Safe

ty d

egre

e ca

n be

impr

oved

ste

pwis

e. S

cale

of d

am c

an b

e m

inim

ized

by

enha

ncem

ent o

fre

tard

ing

func

tion.

Mul

tiple

use

of r

etar

ding

bas

in is

ava

ilabl

e.

Land

use

of re

tard

ing

basi

n af

ter e

nhan

cem

ent o

ffu

nctio

n is

ava

ilabl

e.

Disa

dvan

tage

sLa

ndus

e of

reta

rdin

g ba

sin

shal

l be

regu

late

d.Ap

plic

able

onl

y wh

en g

eolo

gica

lly a

vaila

ble.

Land

acq

uisi

tion

of re

tard

ing

basi

n is

requ

ired.

Dam

is a

pplic

able

onl

y wh

en g

eolo

gica

llyav

aila

ble.

Sin

ce d

am d

evel

opm

ent i

s pl

anne

daf

ter e

nhan

cem

ent o

f ret

ardi

ng fu

nctio

n, in

vest

for t

empo

rary

mea

sure

is re

quire

d.

Proj

ect C

ost(m

illion

pes

o)

1,050

3,230

2,140

800

3,100

3,100

500

500

2,600

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nan

gka

Rive

r

Dam

Marikina River

Sto.

Nin

o

MCG

S

NH

CS

Rosa

rio

Wei

r

Mon

talb

an

V=8

0MCM

1,050

3,230

2,140

800

3,100

3,100

500

500

2,600

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nan

gka

Rive

r

Dam

Marikina River

Sto.

Nin

o

MCG

S

NH

CS

Rosa

rio

Wei

r

Mon

talb

an

V=8

0MCM

1,820

3,230

2,840

800

3,100

3,100

500

500

02,600

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nan

gka

Rive

r

Dam

Marikina River

Sto.

Nin

o

MCG

S

NH

CS

Rosa

rio

Wei

r

Mon

talb

an

V=5

5MCM

Nat

ural

Re

tard

ing

Basi

nA=

1000

ha

1,820

3,230

2,840

800

3,100

3,100

500

500

02,600

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nan

gka

Rive

r

Dam

Marikina River

Sto.

Nin

o

MCG

S

NH

CS

Rosa

rio

Wei

r

Mon

talb

an

V=55

MCM

Floo

d Co

ntro

l Ba

sin

A=40

0ha

So

urce

: JIC

A St

udy

Team

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

65

Tabl

e 4.

32

Alte

rnat

ives

for

Urg

ent F

lood

Man

agem

ent M

easu

res (

Sto.

Nin

o: 2

,900

m3 /s)

Fl

ood

Man

agem

ent

Mea

sure

s fo

r 1/1

00 Y

ears

Floo

dAl

tern

ative

-O-1

Alte

rnat

ive-O

-2Al

tern

ative

-B-1

Alte

rnat

ive-B

-2-1

Alte

rnat

ive-B

-3Al

tern

ative

-B-2

-2

Disc

harg

e Al

locat

ion

Uppe

r Upp

er M

ariki

na R

iver

Dam

+ N

atur

al R

etar

ding

Bas

inDa

m: 6

5 M

CM, N

atur

al Re

tard

ing B

asin:

30

MCM

Chan

nel I

mpr

ovem

ent +

Dam

Dam

: 90M

CM

Dam

+ R

etar

ding

Bas

inDa

m: 5

5MCM

　Na

tura

l Ret

ardin

g Ba

sin:

30M

CM＋

Reta

rding

Bas

in: 5

MCM

Chan

nel I

mpr

ovem

ent +

Dam

(Enh

ance

men

t of R

etar

ding

Bas

in)

Dam

: 90M

CM

Cha

nnel

Impr

ovem

ent

+ D

am +

Ret

ardi

ngBa

sin

Dam

: 65M

CM　

Reta

rdin

g Ba

sin 4

00ha

, 20M

CM

Chan

nel I

mpr

ovem

ent +

Dam

(Enh

ance

men

t of R

etar

ding

Bas

in)

Dam

: 90M

CM

Uppe

r Mar

ikina

Rive

rPh

ase

IV C

ompo

nent

sPh

ase

IV C

ompo

nent

sPh

ase

IV C

ompo

nent

sPh

ase

IV C

ompo

nent

sPh

ase

IV C

ompo

nent

sPh

ase

IV C

ompo

nent

s

Man

gaha

nCu

rrent

Plan

to 2

,400

m3/

sCu

rrent

Plan

to 2

,400

m3/

sCu

rrent

Plan

to 2

,400

m3/

sCu

rrent

Plan

to 2

,400

m3/

sCu

rrent

Plan

to 2

,400

m3/

sCu

rrent

Plan

to 2

,400

m3/

s

Lowe

r Mar

ikina

Rive

rCu

rrent

Pha

se III

Com

pone

nts

Curre

nt P

hase

III C

ompo

nent

sCu

rrent

Pha

se III

Com

pone

nts

Curre

nt P

hase

III C

ompo

nent

sCu

rrent

Pha

se III

Com

pone

nts

Curre

nt P

hase

III C

ompo

nent

s

Pasig

Rive

rPh

ase

II + D

redg

ing to

1,4

00m

3/s

Phas

e II +

Dre

dging

to 1

,400

m3/

sPh

ase

II + D

redg

ing to

1,4

00m

3/s

Phas

e II +

Dre

dging

to 1

,400

m3/

sPh

ase

II + D

redg

ing to

1,4

00m

3/s

Phas

e II +

Dre

dging

to 1

,400

m3/

s

61,6

25.3

65,2

57.5

63,5

18.5

67,6

83.3

66,0

87.7

69,1

39.4

(1.0

00)

(1.0

59)

(1.0

31)

(1.0

98)

(1.0

72)

(1.1

22)

Adva

ntag

esSc

ale o

f Dam

can

be

mini

mize

by

utiliz

ation

of

natu

ral r

etar

ding

basin

.La

ndus

e of

reta

rding

bas

in is

avail

able.

Safe

ty d

egre

e ca

n be

impr

oved

ste

pwise

. Sca

leof

dam

can

be

mini

mize

d by

enh

ance

men

t of

reta

rding

func

tion.

Land

use

of re

tard

ing b

asin

afte

r enh

ance

men

t of

func

tion

is av

ailab

le.

Safe

ty d

egre

e ca

n be

impr

oved

ste

pwise

. Sca

leof

dam

can

be

mini

mize

d by

enh

ance

men

t of

reta

rding

func

tion.

Land

use

of re

tard

ing b

asin

afte

r enh

ance

men

t of

func

tion

is av

ailab

le.

Disa

dvan

tage

sLa

ndus

e of

reta

rding

bas

in sh

all b

e re

gulat

ed.

Appli

cable

only

whe

n ge

ologic

ally

avail

able.

Land

use

of re

tard

ing b

asin

shall

be

regu

lated

.

Dam

is a

pplic

able

only

when

geo

logica

llyav

ailab

le. S

ince

dam

dev

elopm

ent i

s pla

nned

afte

r enh

ance

men

t of r

etar

ding

func

tion,

inve

stfo

r tem

pora

ry m

easu

re is

requ

ired.

Land

acq

uisitio

n of

reta

rding

bas

in is

requ

ired.

Dam

is a

pplic

able

only

when

geo

logica

llyav

ailab

le. S

ince

dam

dev

elopm

ent i

s pla

nned

afte

r enh

ance

men

t of r

etar

ding

func

tion,

inve

stfo

r tem

pora

ry m

easu

re is

requ

ired.

Proje

ct C

ost(m

illion

pes

o)

710

3,230

1,900

800

2,900

2,900

500

500

02,400

Laguna Lake

Mangahan Floodway

Mar

ikin

a Riv

er

(Low

er)

Nang

ka R

iver

Dam

Marikina River

Sto.

Nino

MCG

S

NHCS

Rosa

rioW

eir

Mon

talb

an

V=90

MCM

710

3,230

1,900

800

2,900

2,900

500

500

02,400

Laguna Lake

Mangahan Floodway

Mar

ikin

a Riv

er

(Low

er)

Nang

ka R

iver

Dam

Marikina River

Sto.

Nino

MCG

S

NHCS

Rosa

rioW

eir

Mon

talb

an

V=90

MCM

710

3,230

1,900

800

2,900

2,900

500

500

02,400

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nang

ka R

iver

Dam

Marikina River

Sto.

Nin

o

MCG

S

NHC

S

Rosa

rioW

eir

Mon

talb

an

V=90

MCM

1,820

3,230

2,840

800

2,900

2,900

500

500

02,400

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nan

gka R

iver

Dam

Marikina River

Sto.

Nino

MCG

S

NHC

S

Rosa

rioW

eir

Mon

talb

an

V=55

MCM

Natu

ral

Reta

rdin

g Ba

sin+A

ddito

nal

Capa

city

V=5M

CM

1,450

3,230

2,500

800

2,900

2,900

500

500

02,400

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nang

ka R

iver

Dam

Marikina River

Sto.

Nino

MCG

S

NHC

S

Rosa

rioW

eir

Mon

talb

an

V=65

MCM

Natu

ral

Reta

rdin

g Bas

inA=

1000

ha

1,450

3,230

2,500

800

2,900

2,900

500

500

02,400

Laguna Lake

Mangahan Floodway

Mar

ikin

a Ri

ver

(Low

er)

Nang

ka R

iver

Dam

Marikina River

Sto.

Nino

MCG

S

Floo

d Co

ntro

l Bas

in

A=40

0ha

NHC

S

Rosa

rio

Wei

r

Mon

talb

an

V=65

MCM

So

urce

: JIC

A St

udy

Team

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

66

(5)

Com

pari

son

with

Pro

pose

d M

easu

res b

y W

B S

tudy

Fe

asib

ility

, mea

sure

s ag

ains

t exc

ess

disc

harg

e, e

cono

mic

effi

cien

cy a

nd s

ocia

l im

pact

are

com

pare

d am

ong

Alt

A-2

-1, A

lt B

-3 a

nd th

e pr

opos

ed m

easu

res

by W

B

Stud

y as

show

n in

Tab

le 4

.33.

Tabl

e 4.

33

Com

pari

son

with

Pro

pose

d M

easu

res b

y W

B S

tudy

Alt

A-2

: Dam

Onl

y A

lt B

-3: D

am +

Ret

ardi

ng B

asin

Con

stru

ctio

n W

B S

tudy

D

isch

arge

A

lloca

tion

1,050

3,230

2,140

800

3,100

3,100

1,400

600

500

500

02,600

780

Laguna Lake

Mangahan Floodway

Napindan Channel

Mar

ikin

a Ri

ver

(Low

er)

Pasi

g Ri

ver

Nan

gka

Rive

r

Dam

Marikina River

Sto.

Nin

o

Pasi

g Ri

ver

San Juan River

MCG

S

NH

CS

Rosa

rio

Wei

r

Mon

talb

an

Alte

rnat

ive-

ARe

turn

Perio

d: 1

00-y

ear

Dam

: Lar

geFl

ood

Cont

rol B

asin

: with

out

NH

CS: C

lose

MCG

S: W

ith

PP

V=80

MCM

1,450

3,230

2,500

800

2,900

2,900

1,400

600

500

500

02,400

780

Laguna Lake

Mangahan Floodway

Napindan Channel

Mar

ikin

a Riv

er

(Low

er)

Pasi

g Riv

er

Nang

ka R

iver

Dam

Marikina River

Sto.

Nino

Pasi

g Riv

er

San Juan River

Manila Bay

MCG

S

Floo

d Co

ntro

l Bas

in

A=40

0ha

NHCS

Rosa

rioW

eir

Mon

talb

an

Alte

rnat

ive-

BRe

turn

Perio

d: 1

00-y

ear

Dam

: Med

ium

Floo

d Co

ntro

lBas

inN

HCS

: Clo

seM

CGS:

With

PP

V=65

MCM

Scal

e of

Fa

cilit

y D

am: V

=55M

CM

R

etar

ding

Bas

in: W

ithou

t C

hann

el Im

prov

emen

t:

Pasi

g : 1

,400

m3 /s

N

apin

dan

Can

nel:

With

out

Low

er M

arik

ina:

500

m3 /s

Man

gaha

n Fl

oodw

ay:2

,600

m3 /s

U

pper

Mar

ikin

a : 3

,100

m3 /s

U

pper

-Upp

er M

arik

ina:

3,1

00m

3 /s

Dam

: V=6

5MC

M

Ret

ardi

ng B

asin

: 371

ha(8

site

s)

Cha

nnel

Impr

ovem

ent:

Pa

sig

:1,4

00m

3 /s

Nap

inda

n C

anne

l: w

ithou

t Lo

wer

Mar

ikin

a: 5

00m

3 /s

Man

gaha

n Fl

oodw

ay:2

,400

m3 /s

U

pper

Mar

ikin

a: 2

,900

m3 /s

U

pper

-Upp

er M

arik

ina:

2,9

00m

3 /s

Dam

: H=7

2m

Nat

ural

Ret

ardi

ng B

asin

: 980

ha

Cha

nnel

Impr

ovem

ent:

Pasi

g : 1

,800

m3 /s

N

apin

dan

Can

nel:

800m

3 /s

Low

er M

arik

ina

: 1,2

00m

3 /s

Man

gaha

n Fl

oodw

ay:2

,000

m3 /s

U

pper

Mar

ikin

a : 3

,000

m3 /s

U

pper

-Upp

er M

arik

ina:

2,9

00m

3 /s

Feas

ibili

ty

Hei

ghte

ning

a p

art o

f Pha

se IV

Sec

tion

is re

quire

d.

A

dditi

onal

wor

k fo

r Pha

se II

I and

IV is

not

requ

ired.

In

flow

thro

ugh

Nap

inda

n is

unc

erta

in.

Dre

dgin

g, a

dditi

onal

wor

ks i

n Ph

ase

III

and

IV S

ectio

ns

and

heig

hten

ing

of N

apin

dan

Chan

nel i

s req

uire

d.

Mea

sure

s fo

r Ex

cess

Flo

od

Con

trolle

d by

MC

GS

C

ontro

lled

by M

CG

S

Floo

d ris

k in

crea

se.

Proj

ect C

ost

63,0

75 M

Pes

os (1

00%

) 65

,808

M P

esos

(104

%)

82,7

63 M

Pes

os (1

31％

) So

cial

Impa

ct

Hei

ghte

ning

a p

art o

f Pha

se IV

Sec

tion

is re

quire

d.

Land

acq

uisi

tion

for r

etar

ding

bas

in is

requ

ired.

La

nd a

cqui

sitio

n fo

r N

apin

dan

heig

hten

ing

and

reta

rdin

g ba

sin

is re

quire

d.

Sour

ce: J

ICA

Stud

y Te

am


Final Report 4-67

4.4.5 Project Cost Estimate for Alternatives

Project cost is estimated based on the previous studies, “The Preparatory Study for Pasig-Mairkina River Channel Improvement (Phase III)” conducted by JICA (hereinafter referred to as the “JICA FS”) and “Master Plan for Flood Management in Metro Manila and Surrounding Areas” conducted by WB (hereinafter referred to as the “WB Study”) as shown below.

Table 4.34 Source of Cost Estimation Section/Facility Scale Source & Base Year of Estimation Reference in Original Report

Pasig River

1,300m3/s WB Study in 2011 P5-105 1,400m3/s WB Study in 2011 P5-105

Pasig River Phase2 Phase2 JICA FS in 2010 P6-5 Lower Marikina River Phase3 JICA FS in 2010 P6-5 MCGS MCGS JICA FS in 2010 P6-5

Manggahan Floodway

2,400m3/s WB Study in 2011 P5-105 2,600m3/s WB Study in 2011 P5-105

Upper Marikina River

Phase4 JICA FS in 2010 P6-5 3,100m3/s WB Study in 2011 P6-5

Upper Upper Marikina River

NRB WB Study in 2011 P5-105 RB 20MCM RB 8MCM RB 5MCM CI 2,900m3/s WB Study in 2011 P5-105 CI 3,100m3/s WB Study in 2011 P5-105

Dam

90MCM WB Study in 2011 P5-105 80MCM WB Study in 2011 P5-105 65MCM WB Study in 2011 P5-105 55MCM WB Study in 2011 P5-105

RB: Retarding Basin, CI: Channel Improvement, NRB: Natural Retarding Basin

The following assumptions are applied to estimate the project costs. <WB Study> The following ratios are applied to estimate Engineering Service Cost, Administration Cost and Physical Contingency, referring to the WB Study Report. Since Price Contingency was not estimated in the WB Study, it is estimated as 10% of all other costs considering recent price escalation in Metro Manila.

Engineering Service Cost: 16% of Direct Construction Cost Administration Cost: 35% of Direct Construction Cost and Compensation Cost Physical Contingency: 5% of Direct Construction Cost

<JICA FS> All necessary cost items except price contingency was estimated in the JICA FS, however, compensation, engineering service, administration and physical contingency was not estimated by section/facility. Thus, these costs are estimated by ratio of direct construction cost as shown below. Price Contingency is estimated as 10% of all other costs considering recent price escalation in Metro Manila.


Final Report 4-68

Table 4.35 Project Cost Allocation by Component

Financial Project Cost of Phase III

unit: Million Pesos

年

Direct Construction Consulting Services Compensation Adm.

Phase II Phase III Physical Conting

Non structural Measures

Construction Supervision

Physical Contingency

Base Cost Physical Conting

Base Cost

a b c d e f g h i

2013 0 0 0 97.7 80.6 8.9 17.4 0.9 6.5

2014 630.6 451.4 54.1 65.2 53.7 6 37.8

2015 945.3 675.4 81 65.2 53.7 6 54.6

2016 945.3 675.4 81 65.2 53.7 6 54.6

2017 313.6 220.6 26.7 32.6 26.9 3 18.7

Total 2834.8 2022.8 242.8 325.9 268.6 29.9 17.4 0.9 172.2

0.58358 0.41642

Phas Ⅱ 2834.8 141.7 190.2 156.7 17.4 10.2 0.5 100.5

Phas Ⅲ 2022.8 101.1 135.7 111.9 12.5 7.2 0.4 71.7

Direct construction

cost

Compensation cost

Engineering service cost

Administration cost

Physical contingency

cost

a ,b g d+e i c+e+f

Phas Ⅱ 2834.8 10.2 346.9 100.5 159.6

Phas Ⅲ 2022.8 7.2 247.6 71.7 114

Financial Project Cost of Phase IV

unit: Million Pesos

年

Direct Construction Consulting Services Compensation Adm.

MCGS Phase IV Physical Conting

Non structural Measures

Construction Supervision

Physical Contingency

Base Cost Physical Conting

Base Cost

a b c d e f g h i 2017 40.8 2 4 0.2 1.5

2018 496.2 481.6 48.9 97.7 131.2 11.5 14.1 0.7 28.6

2019 744.8 720.2 73.3 65.2 87.5 7.6 50.8

2020 744.8 720.2 73.3 65.2 87.5 7.6 50.8

2021 744.8 720.2 73.3 65.2 87.5 7.6 50.8

2022 243 235.2 23.9 32.6 43.7 3.8 17.5

Total 2973.6 2877.4 292.7 325.9 478.2 40.1 18.1 0.9 200

0.508221 0.491779

MCGS 2973.6 148.8 165.6 243.0 20.4 3.0 0.1 101.6

Phase IV 2877.4 143.9 160.3 235.2 19.7 15.1 0.8 98.4

Direct constructio

n cost

Compensation cost

Engineering service

cost

Administration cost

Physical contingenc

y cost

a ,b g d+e i c+e+f

MCGS 2973.6 3 408.6 101.6 169.3

Phase IV 2877.4 15.1 395.5 98.4 164.4

Remarks for cost estimate of each section/facility is as follows. (1) Pasig River

Based on the direct construction cost of riverbed excavation to increase flow capacity up to 1,700m3/s which estimated by the WB Study, direct construction cost for channel improvement work is estimated with following manner. It is noted that compensation is not included.


Final Report 4-69

c) Direct Construction Cost Direct Construction Cost: 4,825mil.peso（1,700m3/s） Increase of Flow Capacity: 1,700-1,200＝500m3/s Unit Cost for Flow Capacity Increase: 9.65 mil.peso/1m3/s Flow Capacity Improvement up to 1,300m3/s: (1,300-1,200)×9.65＝965 mil.peso Flow Capacity Improvement up to 1,400m3/s: (1,400-1,200)×9.65＝1,930 mil.peso

d) Compensation Cost

Since the work component is riverbed excavation, compensation is not estimated.

(2) Pasig River Phase2

Price contingency is added to the cost which estimated in the JICA FS.

(3) Lower Marikina Phase3 Price contingency is added to the cost which estimated in the JICA FS. (4) MGCS Price contingency is added to the cost which estimated in the JICA FS.

(5) Upper Marikina

1) Phase4

Price contingency is added to the cost which estimated in the JICA FS.

2) 3,100m3/s Direct construction cost and compensation cost are estimated by target flow capacity ratio based on Phase 4 cost of which target capacity is 2,900m3/s. (6) Manggahan Floodway

1) 2,400m3/s

The following cost estimate is applied based on the WB Study.

Direct Construction Cost: 3,252mil.peso Compensation Cost: 89mil.peso

2) 2,600m3/s

Direct construction cost and compensation cost are estimated by target flow capacity ratio based on the WB Study.

a) Direct Construction Cost

2,400m3/s: 3,252 mil.peso 2,600m3/s: (2,600/2,400)×3,252＝3,523.0 mil.peso

b) Compensation Cost 2,400m3/s: 89mil.peso 2,600m3/s: (2,600/2,400)×89＝96.4 mil.peso

(7) Upper-upper Marikina River

1) Natural Retarding Basin (NRB)

Only compensation cost is estimated based on the WB Study. The unit compensation cost by the WB


Final Report 4-70

Study is expensive, 32 mil. Peso/ha since it includes compensation for houses/building. Thus, 5 mil. peso/ha is applied for compensation of bare land based on the hearing results to DPWH.

2) Retarding Basin (RB) Major works for retarding basin construction with capacity of 8 MCM and 5 MCM is excavation. The direct construction cost is estimated applying unit cost of 300 peso/m3 for excavation, hauling and other works. For the improvement works to 20 MCM capacity, unit price of 200 peso/m3 for embankment is applied.

Table 4.36 Cost Estimate of Retarding Basin Case Cost Item Work Item Unit Q'ty

Unit Cost(peso)

Cost(mil.peso)

RemarksPriceYear

Excavation ｍ3 - 300 - Including Hauling & Finishing 2011

Embankment ｍ3 - 200 - 2011

Total - Urban Area ha 600 32,000,000 19,200 Land + House 2011

Bare Land ha 400 5,000,000 2,000 Land only 2012

Total 21,200 Excavation ｍ3 - 300 - Including Hauling & Finishing 2011

Embankment ｍ3 1,960,000 200 392 2011

Total 392 Urban Area ha - 32,000,000 - Land + House 2011


Total 2,000 Excavation ｍ3 8,000,000 300 2,400 Including Hauling & Finishing 2011


Total 2,400 Urban Area ha - 32,000,000 - Land + House 2011


Total 2,000 Excavation ｍ3 5,000,000 300 1,500 Including Hauling & Finishing 2011


Total 1,500 Urban Area ha - 32,000,000 - Land + House 2011


Total 1,250

Compensation

Direct ConstructionCost

Compensation

NRB

20 MCM

8 MCM

5MCM


Compensation


Compensation


3) Channel Improvement Works (CI) The direct construction cost for channel improvement to the capacity of 2,900 m3/s is estimated based on the WB Study of which major works is embankment. The direct construction cost for channel improvement to the capacity of 3,100 m3/s is estimated applying capacity ratio. The compensation cost is estimated based on Phase 4 unit cost by the JICA FS applying channel length. a) Direct Construction Cost

2,900m3/s: 1,341 mil.peso (WB Study) 3,100m3/s: (3,100/2,900)×1,341＝1,433.5 mil.peso

b) Compensation Cost Phase IV Section (Upper Marikina, 6.8km Length) 2,900m3/s: 15.1 mil.peso 3,100m3/s: 16.1 mil.peso

Upper Upper Marikina Section (14.2km Length) 2,900m3/s: (14.2/6.8) x 15.1 = 31.5 mil.peso 3,100m3/s: (14.2/6.8) x 16.1 = 33.6 mil.peso


Final Report 4-71

(8) Dam

The unit construction cost per 1m dam height is estimated based on the direct construction cost estimated by the WB Study. The necessary dam height for storage capacity is estimated based on H-V curve formulated by the Study, and the direct construction cost is estimated as follows.

Table 4.37 Cost Estimate of Dam

Case Dam Height (m) Direct Construction Cost

(mil.peso) 55 MCM 68 8,160 60 MCM 69 8,280 65 MCM 71 8,520 80 MCM 75 9,000 90 MCM 78 9,360

(9) Cost for Each Section and Estimation of Current Price Since base years of cost estimation is different between the JICA FS (2010) and the WB Study (2011), the current price as of year 2012 is estimated applying the price escalations based on CPI of Metro Manila as shown in Table 10. The prices before and after conversion is shown in Table 12 and Table 13, respectively. Applied price escalations are as follows.

2010 2012: 1.070 2011 2012: 1.029

Table 4.38 CPI of Metro Manila Year 2010 2011 2012 CPI 116.3 120.9 124.4

(10) Project Costs of Proposed Alternatives

The summary of project cost estimate of proposed alternatives is shown in Table 4.39 while the breakdown of each alternative is shown in Table 4.42.

Table 4.39 Summary of Project Cost of Proposed Alternatives (2012 Price)

Scale Alternatives Components Project Cost

（million peso） 1/30 O PhaseIV Component＋NRB:30MCM 20,131.9

A PhaseIV Component+NRB:30MCM + Manggahan Floodway Improvement 22,170.8

B PhaseIV Component +RB:35MCM 25,034.1 1/100 A-1 Dam:55MCM+NRB:30MCM 59,866.0

A-2-1 Dam:80MCM 63,074.9 A-3 Dam:55MCM+RB:20MCM 66,110.7

A-2-2 Dam:80MCM* 66,742.1 O-1 Dam:65MCM+NRB:30MCM 59,694.5 O-2 Dam:90MCM 62,772.4 B-1 Dam:55MCM+RB:35MCM 61,479.3

B-2-1 Dam:90MCM* 65,064.5 B-3 Dam:65MCM+RB:20MCM 65,808.3

B-2-2 Dam:90MCM* 66,439.6 Note) NRB: Natural Retarding Basin, RB: Retarding Basin, *After Dam, RB will be demolished.

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

72

Tabl

e 4.

40

Proj

ect C

ost b

efor

e C

onve

rsio

n un

it: m

illio

n pe

so

Sect

ion

Con

tent

s

Dire

ct

cons

truct

ion

cost

Com

pens

atio

n co

st

Engi

neer

ing

serv

ice

cost

Ad

min

istra

tion

cost

Phys

ical

co

ntin

genc

y co

st

Pric

e co

ntin

genc

y co

st

Tota

l R

emar

ks

a b

c=a*

16%

d=

(a+b

)*3.

5%

e=a*

5%

f=Σ(

a～e)

*10%

g=

Σ(a～

f)

Pasi

g R

iver

1,

300m

3 /s

965.

0

0.0

15

4.4

33

.8

48.3

12

0.2

1,

321.

7

2011

1,40

0m3 /s

1,

930.

0

0.0

30

8.8

67

.6

96.5

24

0.3

2,

643.

2

2011

Pasi

g R

iver

Pha

se2

Phas

e2

2,83

4.8

10

.2

346.

9

100.

5

159.

6

345.

2

3,79

7.2

20

10

Low

er M

arik

ina

Riv

er

Phas

e3

2,02

2.8

7.

2

247.

6

71.7

11

4.0

24

6.3

2,

709.

6

2010

MC

GS

MC

GS

2,97

3.6

3.

0

408.

6

101.

6

169.

3

365.

6

4,02

1.7

20

11

Man

ggah

an F

lood

way

2,

400m

3 /s

3,25

2.0

89

.0

520.

3

116.

9

162.

6

414.

1

4,55

4.9

20

11

2,60

0m3 /s

3,

523.

0

96.4

56

3.7

12

6.7

17

6.2

44

8.6

4,

934.

6

2011

Upp

er M

arik

ina

Riv

er

Phas

e4

2,87

7.4

15

.1

395.

5

98.4

16

4.4

35

5.1

3,

905.

9

2010

3,10

0m3 /s

3,

075.

8

16.1

42

2.8

10

5.2

17

5.7

37

9.6

4,

175.

2

2010

Upp

er U

pper

Mar

ikin

a R

iver

NR

B 0.

0

21,2

00.0

0.

0

742.

0

0.0

2,

194.

2

24,1

36.2

20

11

RB

20M

CM

2,

792.

0

2,00

0.0

44

6.7

16

7.7

13

9.6

55

4.6

6,

100.

6

2011

RB

8MC

M

2,40

0.0

2,

000.

0

384.

0

154.

0

120.

0

505.

8

5,56

3.8

20

11

RB

5MC

M

1,50

0.0

1,

250.

0

240.

0

96.3

75

.0

316.

1

3,47

7.4

20

11

CI 2

,900

m3 /s

1,

341.

0

31.5

21

4.6

48

.0

67.1

17

0.2

1,

872.

4

2011

CI 3

,100

m3 /s

1,

433.

5

33.6

22

9.4

51

.3

71.7

18

2.0

2,

001.

5

2011

Dam

90M

CM

9,

360.

0

0.0

1,

497.

6

327.

6

468.

0

1,16

5.3

12

,818

.5

2011

80M

CM

9,

000.

0

0.0

1,

440.

0

315.

0

450.

0

1,12

0.5

12

,325

.5

2011

65M

CM

8,

520.

0

0.0

1,

363.

2

298.

2

426.

0

1,06

0.7

11

,668

.1

2011

55M

CM

8,

160.

0

0.0

1,

305.

6

285.

6

408.

0

1,01

5.9

11

,175

.1

2011

N

ote)

NR

B: N

atur

al R

etar

ding

Bas

in, R

B: R

etar

ding

Bas

in, C

I: C

hann

el Im

prov

emen

t So

urce

of i

tem

a, b

, c, d

and

e: J

ICA

SF R

epor

t, C

ost f

or C

I 3,1

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3 /s is

est

imat

ed b

ased

on

cost

for C

I 2,9

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3 /s.

The

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41

Proj

ect C

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Con

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ion

(201

2 Pr

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it: m

illio

n pe

so

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ctio

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0

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15

8.9

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.8

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.6

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3

Man

gaha

n Fl

oodw

ay

2,40

0m3 /s

3,

346.

3

91.6

53

5.4

12

0.3

16

7.3

42

6.1

4,

687.

0

2,60

0m3 /s

3,

625.

2

99.2

58

0.0

13

0.4

18

1.3

46

1.6

5,

077.

7

Upp

er M

arik

ina

Riv

er

Phas

e4

3,07

8.8

16

.2

423.

2

105.

3

175.

9

380.

0

4,17

9.4

3,10

0m3 /s

3,

291.

1

17.2

45

2.4

11

2.6

18

8.0

40

6.2

4,

467.

5

Upp

er U

pper

Mar

ikin

a R

iver

NR

B 0.

0

21,8

14.8

0.

0

763.

5

0.0

2,

257.

8

24,8

36.1

RB

20M

CM

2,

873.

0

2,00

0.0

45

9.7

17

2.6

14

3.6

57

0.7

6,

219.

6

RB

8MC

M

2,46

9.6

2,

000.

0

395.

1

158.

5

123.

5

520.

5

5,66

7.2

R

B 5M

CM

1,

543.

5

1,25

0.0

24

7.0

99

.1

77.2

32

5.3

3,

542.

1

CI 2

,900

m3 /s

1,

379.

9

32.4

22

0.8

49

.4

69.0

17

5.1

1,

926.

6

CI 3

,100

m3 /s

1,

475.

1

34.6

23

6.1

52

.8

73.8

18

7.3

2,

059.

7

Dam

90M

CM

9,

631.

4

0.0

1,

541.

0

337.

1

481.

6

1,19

9.1

13

,190

.2

80M

CM

9,

261.

0

0.0

1,

481.

8

324.

1

463.

1

1,15

3.0

12

,683

.0

65M

CM

8,

767.

1

0.0

1,

402.

7

306.

8

438.

4

1,09

1.5

12

,006

.5

55M

CM

8,

396.

6

0.0

1,

343.

5

293.

9

419.

8

1,04

5.4

11

,499

.2

N

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B: N

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al R

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t


Final Report 4-74

(11) Project Cost of WB Proposal

The project cost of proposed measures by the WB (Alternative-02) is estimated adding engineering service cost, administration cost, physical contingency and Price contingency cost to the direct construction cost and compensation cost estimated by the WB Study. For comparison purpose, the cost for San Juan River improvement is excluded since it was not estimated in the JICA FS. On the other hand, the project costs for Phase II and Phase III project based on the JICA FS are added. The breakdown of project cost in 2011 price and 2012 price are shown in Table 4.43.

Table 4.42(1) Project Cost of WB Proposed Measures (2011 Price)

unit: million peso

Section Contents Direct

construction cost

Compensation cost


Administration cost


cost

Price contingency

cost Total

Pasig River Dredging 4,825.0 - 772.0 168.9 241.3 600.7 6,607.9

Phase 2※ 2,948.2 10.6 360.8 104.5 166.0 359.0 3,949.1 Napindan Chanel Heightening of Parapet 98.0 - 15.7 3.4 4.9 12.2 134.2

Lower Marikina River

Dredging and Heightening 186.0 - 29.8 6.5 9.3 23.2 254.8

Phase 3※ 2,103.7 7.5 257.5 74.6 118.6 256.2 2,818.1

MCGS - - - - - - - -

Mangahan Floodway

Dredging 3,252.0 89.0 520.3 116.9 162.6 414.1 4,554.9


Dyke and Excavation 5,601.0 4,309.0 896.2 346.9 280.1 1,143.3 12,576.5


Dyke and Excavation 1,341.0 31,521.0 214.6 1,150.2 67.1 3,429.4 37,723.3

Dam H=72m 8,626.0 - 1,380.2 301.9 431.3 1,073.9 11,813.3

Total 28,980.9 35,937.1 4,447.1 2,273.8 1,481.2 7,312.0 80,432.1 ※JICA FS Cost converted to 2011 Price

Table 4.43(2) Project Cost of WB Proposed Measures (2012 Price)

2012 価格

unit:million peso

Section Contents Direct

construction cost

Compensation cost

Engineering service

cost

Administration cost

Physical contingen

cy cost

Price contingen

cy cost Total

Pasig River Dredging 4,964.9 - 794.4 173.8 248.2 618.1 6,799.4

Phase 2※ 3,033.2 10.9 371.2 107.5 170.8 369.4 4,063.0

Napindan Chanel Heightening of Parapet 100.8 - 16.1 3.5 5.0 12.5 137.9

Lower Marikina River

Dredging and Heightening 191.4 - 30.6 6.7 9.6 23.8 262.1 Phase 3※ 2,164.4 7.7 264.9 76.7 122.0 263.5 2,899.2

MCGS - - - - - - - -

Mangahan Floodway

Dredging 3,346.3 91.6 535.4 120.3 167.3 426.1 4,687.0


Dyke and Excavation 5,763.4 4,434.0 922.1 356.9 288.2 1,176.5 12,941.1


Dyke and Excavation 1,379.9 32,435.1 220.8 1,183.5 69.0 3,528.8 38,817.1

Dam H=72m 8,876.2 - 1,420.2 310.7 443.8 1,105.1 12,156.0

Total 29,820.5 36,979.3 4,575.7 2,339.6 1,523.9 7,523.8 82,762.8 Price in 2012, ※JICA FS

(12) Comparison of Project Costs Comparison of proposed project costs between the JICA Study and the WB Study is summarized in Table 4.44.


Final Report 4-75

Table 4.43 Comparison of Project Cost between JICA Study and WB Study

Section Contents JICA Study

A-2-1: CI + Dam

JICA Study B-3:

CI + Dam + RB WB Study

Pasig River Dredging 1,400m3/s 2,720.0 2,720.0 -

1,800m3/s - - 6,799.4

Pasig River Phase2 Phase2 4,063.0 4,063.0 4,063.0

Napindan Chanel Heightening of Parapet - - 137.9

Lower Marikina River Phase3 2,899.2 2,899.2 2,899.2

Dredging and Heightening - - 262.1

MCGS MCGS 4,303.3 4,303.3 -

Mangahan Floodway 2,400m3/s - 4,687.0 4,687.0

2,600m3/s 5,077.7 - -


Phase4 - 4,179.4 -

3,100m3/s 対応 4,467.5 - -

Dyke and Excavation - - 12,941.1


NRB with Future Dyke Heightening (3,100m3/s in Channel) 24,801.5 -

NRB with Future RB Development (2,900m3/s in Channel + 20MCM in RB) - 22,803.7

RB 20MCM - 6,219.6 -

CI 2,900m3/s - 1,926.6 -

CI 3,100m3/s 2,059.7 - -

Dyke and Excavation - - 38,817.1

Dam

Dam 80MCM H=75m 12,683.0 - -

Dam 65MCM H=71m - 12,006.5 -

Dam H=72m - - 12,156.0

Total 63,074.9 65,808.3 82,762.8

4.5 Investigation of Appropriateness of Measures to Floods

The appropriateness of measures to floods is investigated by Economic Evaluation taking into consideration this project forms a part of the public investment in order to reduce floods damage in the Metro Manila.

4.5.1 Economic Cost The market prices of Pasig River Dredging, Pasig River Phase 2, Lower Marikina River, MCGS, Manggahan Floodway, Upper Marikina River, Dam are converted to the economic prices by multiplying the conversion factor shown below. Table 4.45 shows the economic cost for the Target Case. The economic cost descriptions for all cases are shown in Appendix.

The conversion factors of the past investigation (Preparatory Study for Pasig-Marikina River Channel Improvement Project (Phase III), hereinafter, referred to as “Preparatory Study”) are used in this study.

Table 4.44 Conversion Factors

Item Conversion Factors

1 Direct Construction Cost 0.79

2 Compensation 0.57

3 Engineering Service 1.19

4 Government Administration 0.97

5 Physical Contingency 0.93


Final Report 4-76

Table 4.45 Economic Cost of the Target Case (million pesos)

Alternatives Direct

construction cost

Compensation cost


Administration cost


cost Total

Ｏ 11,695.6 73.9 2,418.0 502.9 760.0 15,450.3

Ａ 12,868.1 78.8 2,694.9 553.6 830.5 17,025.8

Ｂ 13,699.4 807.1 2,901.0 632.8 878.0 18,918.3

Ａ－１ 20,285.9 12,513.2 4,482.7 1,613.0 1,267.0 40,161.8

Ａ－２－１ 22,134.1 12,513.2 4,928.3 1,693.5 1,375.9 42,645.0

Ａ－３ 23,720.9 12,513.2 5,310.7 1,831.7 1,469.2 44,845.7

Ａ－２－２ 24,085.0 12,513.2 5,398.4 1,847.3 1,490.8 45,334.7

Ｏ－１ 20,190.5 12,508.3 4,465.4 1,608.6 1,260.1 40,032.9

Ｏ－２ 21,963.4 12,508.3 4,892.7 1,686.0 1,364.4 42,414.8

Ｂ－１ 21,117.2 12,508.3 4,688.8 1,692.3 1,314.6 41,321.1

Ｂ－２―１ 23,182.8 12,508.3 5,186.6 1,782.1 1,436.2 44,096.0

Ｂ－３ 23,550.3 12,508.3 5,275.2 1,824.0 1,457.8 44,615.5

Ｂ－２－２ 23,914.4 12,508.3 5,362.9 1,839.7 1,479.3 45,104.5

4.5.2 Economic Benefit The benefit in a Flood Prevention Project is the expected amounts of average annual damage reduction prevented by the project based on the difference of damage reduction amount between With Project Case and Without Project Case.

To put it concretely, details are given below.

(1) Arrangement of the assets in the probable flood area

(2) Calculation of the flood damage amounts by each occurrence probability through the flood simulation in Without Project Case

(3) Calculation of the expected amounts of average annual damage reduction based on the flood damage amounts both in With Project Case and Without Project Case

Table 4.47 shows the detail of Flood Damage.

Table 4.46 Detail of Flood Damage Division Detail

Direct Damage

Damage to Residential Buildings Damage to Household Effects Damage to Depreciable Assets of Business Establishments Damage to Inventories of Business Establishments Damage to Agricultural Crops Damage to Infrastructure

Indirect Damage

Loss of Interruption of Business Activities Emergency Cleaning Cost for Household Emergency Measure for Business Establishments


Final Report 4-77

(1) Assets in the probable flood area

Table 4.47 Assets in the probable flood area Item Quantity Assets（Pesos）

Number of Residential Buildings 2,703,072 511,421,308,169

Residential Area (m2) 132,450,550 -

Number of Household 2,703,072 -

Number of a Household 11,623,212 -

Household Effects - 257,873,112,047

Number of Business Establishments (Manufacturing)

12,480 -

Depreciable Assets - 74,218,756,576

Stock Inventories - 62,659,009,122

Number of Business Establishments (Retailing)

311,581 -

Depreciable Assets - 90,371,391,749

Stock Inventories - 765,461,898,115

Cultivated Land Area (m2) 6,911,629 -

Crops - 27,646,515 Note; Each unit value is estimated below by multiplying CPI based on the past investigation (Detailed

Engineering Design of Pasig-Marikina River Channel Improvement Project, (hereinafter, referred to as ”Detailed Investigation”).

・Residential Building ：189,200 Pesos/Building ・Household Effects：95,400 Pesos/Household ・Depreciable Assets of Business Establishments (Manufacturing)：5,947,100 Pesos ・Stock Inventories of Business Establishments (Manufacturing)：7,241,400 Pesos ・Depreciable Assets of Business Establishments (Retailing)：201,100 Pesos ・Stock Inventories of Business Establishments (Retailing)：2,456,700 Pesos ・Crops：40,000 Pesos/ha

(2) Flood Damage

1) Direct Damage

a) Damage to Residential Buildings The damage to residential buildings in the probable flood area is estimated as follows.

Damage to Residential Building = Assets Amount of Residential Buildings in a unit area x Damage Rate of Residential Buildings in inundation depth

Damage Rate of Residential Buildings in inundation depth is shown below.

Table 4.48 Damage Rate of Residential Buildings in inundation depth Inundation Depth Less than 0.5m 0.5 m～0.99 m 1.0 m～1.99 m 2.0 m～2.99 m 3.0 m and over

Damage Rate 0.092 0.119 0.266 0.580 0.834 Source: The Manual of Economical Investigation of Flood Disaster (the Ministry of Land, Infrastructure and

Transportation, Japan 2005 April)

b) Damage to Household Effects

The damage to household effects in the probable flood area is estimated as follows. Damage to Household Effects = Amounts of Household Effects in a unit area x Damage Rate of

Household Assets in inundation depth

Damage Rate of Household Effects in inundation depth is shown below.


Final Report 4-78

Table 4.49 Damage Rate of Household Assets in inundation depth Inundation Depth Less than 0.5m 0.5 m ～0.99 m 1.0 m ～1.99 m 2.0 m ～2.99 m 3.0 m and over

Damage Rate 0.145 0.326 0.508 0.928 0.991 Source: The Manual of Economical Investigation of Flood Disaster (the Ministry of Land, Infrastructure and

Transportation, Japan 2005 April) c) Damage to Business Establishments

The damage to business establishments in the probable flood area is estimated as follows. Damage to Depreciable Assets = Amounts of Depreciable Assets in a unit area x Damage Rate

of Depreciable Assets in inundation depth Damage to Stock Inventories = Amounts of Stock Inventories in a unit area x Damage Rate of

Stock Inventories in inundation depth

Damage Rate of Business Establishments in inundation depth is shown below.

Table 4.50 Damage Rate of Depreciable Assets and Stock Inventories in inundation depth Inundation Depth Less than 0.5 m 0.5 m～0.99 m 1.0 m～1.99 m 2.0 m～2.99 m 3.0 m and over

Damage Rate (Depreciable Assets)

0.232 0.453 0.789 0.966 0.995

Damage Rate (Stock Inventories)

0.128 0.267 0.586 0.897 0.982

Source: The Manual of Economical Investigation of Flood Disaster (the Ministry of Land, Infrastructure and Transportation, Japan 2005 April)

d) Damage to Agricultural Crops

The damage to agricultural crops is estimated as follows. Damage to Agricultural Crops = Amount of Agricultural Crops in a unit area x Damage Rate of

Agricultural Crops in inundation depth

Damage Rate of Agricultural Crops in inundation depth is shown below

Table 4.51 Damage Rate of Agricultural Crops in inundation depth Inundation Depth Less than 0.5 m 0.5 m～0.99 m 1.0 m～1.99 m 2.0 m～2.99 m 3.0 m and over

Damage Rate (7 days and over)

0.67 0.74 0.91 0.91 0.91

Source: The Manual of Economical Investigation of Flood Disaster (the Ministry of Land, Infrastructure and Transportation, Japan 2005 April), Average Value of Cultivated Field

e) Damage to Infrastructure

Damage to Infrastructure is 35% of Total Assets Amount in the same way as “Preparatory investigation”.

2) Indirect Damage Indirect Damage is 10% of Total Direct Damage in the same way as “Preparatory Investigation”. (3) Damage Amount

Table 4.53 shows the damage amount, 112,312 million Pesos for 30- probability year flow amount and 182,916 million Pesos for 100-probability year flow amount.


Final Report 4-79

Table 4.52 Damage Amount by Probability year ITEM

2-probability year 5-probability year 10-probability year 20-probability year 30-probability year 50-probability year 100-probability year

Number of Residential Buildings 2,231,905,354 6,553,171,480 8,701,915,032 10,718,881,437 12,338,687,289 15,008,257,030 19,793,054,564

Household Effects 2,231,905,354 6,553,171,480 8,701,915,032 10,718,881,437 12,338,687,289 15,008,257,030 19,793,054,564

Number of Business

Establishments (Manufacturing)

Depreciable Assets 836,532,676 2,573,997,642 3,371,030,413 4,063,096,629 4,619,283,775 5,690,163,598 7,578,291,351

Stock Inventories 1,018,591,871 3,134,190,871 4,104,686,256 4,947,370,639 5,624,603,845 6,928,545,119 9,227,596,473

Number of Business

Establishments (Retailing)

Depreciable Assets 557,744,554 1,716,171,057 2,247,579,691 2,709,003,583 3,079,832,315 3,507,274,298 5,052,702,482

Stock Inventories 6,813,580,532 20,965,278,148 27,457,130,920 33,094,028,355 37,624,187,210 46,346,531,390 61,725,381,341

Crops 2,008,619 3,832,554 4,709,093 5,181,819 5,397,013 5,570,595 5,810,989

Sub Total 13,692,268,958 41,499,813,231 54,588,966,438 66,256,443,899 75,630,678,734 92,494,599,059 123,175,891,764

Infrastructure 4,792,294,135 14,524,934,631 19,106,138,253 23,189,755,365 26,470,737,557 32,373,109,671 43,111,562,117

Indirect Damage 1,848,456,309 5,602,474,786 7,369,510,469 8,944,619,926 10,210,141,629 12,486,770,873 16,628,745,388

Total 20,333,019,403 61,627,222,649 81,064,615,160 98,390,819,190 112,311,557,920 137,354,479,602 182,916,199,270

Damage Amount （Pesos）

(4) (4) Expected Amount of Average Annual Damage Reduction Consequently the expected amount of average annual damage reduction can be estimated about 25,671 thousand Pesos for 30-probability year flow amount and 28,937 thousand Pesos for 100-probability year flow amount as shown below, which is calculated by multiplying the amount of average annual damage corresponding to probable flood with occurrence probability and by accumulating the annual damage of each probable flood.

Table 4.53 Expected Amount of Average Annual Damage Reduction (30-probability year flow amount) 1,000 Pesos

①

Without Project

②

With Project

③

Damage

Reduction (①

-②）

12,294,036

19,428,628

23,915,014

25,670,867

0.100

0.050

0.017

98,390,819

112,311,558

Sectional

probability

12,294,036

7,134,592

4,486,386

1,755,853

98,390,819

112,311,558

40,980,121

71,345,919

89,727,717

0.3000

0

0

0

0 105,351,189

20,333,019

61,627,223

81,064,615

20,333,019

61,627,223

81,064,615

2,860

3,030

1/2

1/5

1/10

1/20

1/30

Size of Flow

(m3/s)

Average Annual

Exceedance

Probability

1,620

2,290

2,670

Damage Amount

Sectional

Average

Damage

Amount of

Average

Annual Damage

Expected

Amount of

Average Annual

Damage

Reduction

Table 4.54 Expected Amount of Average Annual Damage Reduction (100-probability year flow amount) 1000 Pesos

①

Without Project

②

With Project

③

Damage

Reduction (①

-②）

12,294,036

19,428,628

23,915,014

25,670,867

27,335,307

28,936,661

12,294,036

7,134,592

4,486,386

1,755,853

1,664,440

1,601,353

124,833,019

160,135,339

0.300

0.100

0.050

0.017

0.013

0.010

40,980,121

71,345,919

89,727,717

105,351,189

0

20,333,019

61,627,223

81,064,615

98,390,819

112,311,558

137,354,480

182,916,199

0

0

0

0

0

0

20,333,019

61,627,223

81,064,615

98,390,819

112,311,558

137,354,480

182,916,199

1/2

1/5

1/10

1/20

1/30

1/50

1/100

Expected

Amount of

Average AnnualDamage

Reduction

Size of Flow

(m3/s)

Average Annual

ExceedanceProbability

Damage Amount

Sectional

AverageDamage

Sectional

probability

Amount of

AverageAnnual Damage

The map of areas likely to be inundated by probability year are shown in Figures below.


Final Report 4-80

Figure 4.63 Map of areas likely to be inundated by probability year（1/2、1/5）



Final Report 4-81


Figure 4.66 Map of areas likely to be inundated by probability year（1/100）


Final Report 4-82

4.5.3 Economic Evaluation

The economic evaluation for 13 cases (3-case under 30-year return period and 10-case of 100-year return period) shown in Table 4.56 is carried out by utilizing both the abovementioned economic cost and benefit. 13 cases are confirmed to be expected on a economic benefits as a result of high cost-effectiveness as organized into the Table4.57. Economic Internal Rate of Return (EIRR)

Although there is a discrepancy between cases that 3-case under 30-year return period shows over 25% of EIRR and 10-case of 100-year return period shows 17% of EIRR range, all cases have a high cost-effectiveness because of the value far above 15% of EIRR.

Net Present Value (NPV) All cases have a high cost effect judging from that the benefit exceeds the economic cost greatly, yet there is a discrepancy between 3-case under 30-year return period with over 40,000 Million Pesos of NPV and 10-case of 100-year return period with the range between 8,000 Million Pesos and 11,000 Million Pesos of NPV in a manner similar to EIRR.

Benefit Cost Ratio (B/C Ratio) A similar relation holds for B/C Ratio. Although there is a discrepancy 3-case under 30-year return period showing over 3 of the B/C Ratio and 10-case of 100-year return period showing the B/C Ration raging between 1.3 and 1.5, all cases have a high cost-effectiveness because of the value far above 1 of B/C Ratio.

The case showing highest value for EIRR and B/C among 13 cases is the case ① (Phase IV Component Buildup Plan). As concerns NPV, the case ② (Alternative Plan A)) comes first. From this, meanwhile 3-case under 30-year return period indicates high evaluation, there is no big difference between 10-case of 100-year return period. The cash flows for all cases are shown in Appendix.

Table 4.55 Investigation Cases

Return Period Case Alternative

Economic Internal Rate of Return (EIRR)

Net Present Value (NPV)

Benefit Cost Ratio (B/C Ratio)

1/30 ① Alternative Plan O* 63.50% 91,769 Million Pesos 8.1 ② Alternative Plan A 62.60% 98,136 Million Pesos 7.9 ③ Alternative Plan B 28.00% 40,868 Million Pesos 3.7

1/100 ④ Alternative Plan (A-1) 17.60% 10,973 Million Pesos 1.4 ⑤ Alternative Plan (A-2-1) 17.30% 9,854 Million Pesos 1.4 ⑥ Alternative Plan (A-3) 17.00% 8,689 Million Pesos 1.3 ⑦ Alternative Plan (A-2-2) 17.00% 8,542 Million Pesos 1.3 ⑧ Alternative Plan (O-1) 17.70% 11,259 Million Pesos 1.5 ⑨ Alternative Plan (O-2) 17.40% 10,189 Million Pesos 1.4 ⑩ Alternative Plan (B-1) 17.50% 10,591 Million Pesos 1.4 ⑪ Alternative Plan (B-2-1) 17.20% 9,369 Million Pesos 1.4 ⑫ Alternative Plan (B-3) 17.10% 9,024 Million Pesos 1.3 ⑬ Alternative Plan (B-2-2) 17.10% 8,877 Million Pesos 1.3

* : Design Flood Discharge of 2,900m3/s is reevaluated as 1/20 years flood as previously mentioned.

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peak

Fict

iona

l Hye

togr

aph

Hye

togr

aph

base

d on

pro

babl

e ra

infa

ll in

tensit

ies b

y ra

infa

ll du

ratio

ns o

f Por

t Are

a

Type

1: T

ypho

on O

ndoy

Typ

e O

bser

ved

Hye

togr

aph

Type

2: M

iddl

e-pe

ak F

ictio

nal H

yeto

grap

h H

yeto

grap

h ba

sed

on p

roba

ble

rain

fall

inten

sitie

s by

ra

infa

ll du

ratio

ns o

f Por

t Are

a

Obs

erve

d 7

Hye

togr

aphs

+

Mid

dle-

peak

Fi

ction

al

Hye

togr

aph

Evalu

ation

JIC

A Pr

epar

atory

Stu

dy ap

plied

sam

e meth

od as

JICA

Mas

ter P

lan in

1990

. WB

Stud

y an

alyze

d Ty

phoo

n O

ndoy

Typ

e and

Mid

dle-

peak

Fict

iona

l Typ

e and

appl

ied T

ypho

on O

ndoy

Ty

pe.

It

is ne

cess

ary

to an

alyze

var

ious

hye

togr

aphs

sinc

e it i

s unc

ertai

n th

at w

hich

hye

togr

aph

with

enlar

gem

ent t

o pr

obab

le ra

infa

ll ca

uses

the l

arge

st pe

ak d

ischa

rge.

In th

is St

udy,

anot

her 6

hye

togr

aphs

bes

ide

Typh

oon

Ond

oy T

ype

and

Mid

dle-

peak

Fict

iona

l Typ

e is

anal

yzed

and

con

clude

d th

at pe

ak d

ischa

rge

and

nece

ssar

y ca

pacit

y of

stor

age

facil

ity b

ecom

es m

axim

um w

hen

Typh

oon

Ono

dy T

ype i

s app

lied.

Estim

ation

of

Basin

Ave

rage

Ra

infa

ll

Obj

ectiv

e Im

porta

nt It

em to

estim

ate p

roba

ble r

ainfa

ll, p

eak

disc

harg

e and

scale

of s

tora

ge fa

cility

(cap

acity

) con

sequ

ently

Estim

ation

M

ethod

of

Ba

sin

Aver

age

Rain

fall

Rain

fall

at Po

rt A

rea x

Rain

fall A

djus

tmen

t Coe

fficie

nt

Esti

mate

d as

uni

form

rain

fall

in w

hole

area

Ty

pe 1

: Typ

hoon

Ond

oy T

ype

Thi

esse

n M

ethod

and A

djus

tmen

t by

IDW

Meth

od

Esti

mate

d ea

ch 3

4 Th

iesse

n Po

lygo

n Ty

pe 2

: Mid

dle-

peak

Fict

iona

l Hye

togr

aph

IDW

Meth

od

Esti

mate

d fo

r 3 S

ub-b

asin

s

Adj

usted

by

Thies

sen

Meth

od a

nd I

DW

Meth

od b

ased

on

obse

rved

rain

fall

Evalu

ation

JIC

A Pr

epar

atory

Stu

dy ap

plied

sam

e meth

od as

JICA

Mas

ter P

lan in

1990

. 199

0 M

aster

Plan

did

not

cons

ider

spati

al va

riatio

n du

e to

lack

of d

ata. I

n W

B St

udy,

meth

ods t

o an

alyze

sp

atial

and

time v

ariat

ion

wer

e app

lied

base

d on

rece

nt d

ata.

Sp

atial

varia

tion

shall

be

cons

ider

ed to

esti

mat

e ba

sin a

vera

ge ra

infa

ll ac

cura

tely.

Thus

, in

this

Stud

y, m

ethod

s to

anal

yze

spati

al an

d tim

e va

riatio

n ar

e ap

plied

bas

ed o

n da

ta af

ter

1994

.

Des

ign

Rain

fall

Dur

ation

O

bjec

tive

Item

whi

ch af

fect

peak

disc

harg

e and

scale

of s

tora

ge fa

cility

(cap

acity

), de

pend

ing

on b

asin

char

acte

ristic

s suc

h as

bas

in ar

ea, s

lope

, lan

duse

and

so o

n.

A

pplie

d D

esig

n Ra

infa

ll D

urati

on

2 da

ys r

ainfa

ll is

appl

ied t

o co

ver

obse

rved

rain

fall

dura

tion

of p

ast f

lood

s.

2 da

ys r

ainfa

ll is

appl

ied t

o co

ver

obse

rved

rain

fall

dura

tion

of p

ast f

lood

s.

Rel

atio

n be

twee

n ra

infa

ll an

d w

ater

lev

el i

s an

alyz

ed.

Due

to it

s hig

h co

rrel

atio

n, 1

day

rain

fall

is a

pplie

d.

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

84

Item

JIC

A Pr

epar

atory

Stu

dy

WB

Stud

y D

ata C

olle

ction

Sur

vey

(TH

IS S

TUD

Y)

Evalu

ation

Bo

th JI

CA S

tudy

and

WB

Stud

y ap

plied

2 d

ays r

ainfa

ll to

cove

r the

obs

erve

d ra

infa

ll du

ratio

ns. H

owev

er, p

recip

itatio

n un

til fl

ood

conc

entra

tion

time i

s the

mos

t im

porta

nt in

runo

ff an

alysis

. Th

us, c

orre

latio

ns o

f 1 d

ay ra

infa

ll an

d 2

days

rain

fall

with

wat

er le

vel a

re ex

amin

ed an

d it

is fo

und

that

corre

latio

n of

1 d

ay ra

infa

ll is

muc

h hi

gher

than

2 d

ays r

ainfa

ll. S

ince

it d

oes

not e

ffect

to ru

noff

analy

sis th

at 1

day

rain

fall

does

not

cove

r obs

erve

d ra

infa

ll, it

is ap

prop

riate

to ap

ply

1 da

y ra

infa

ll.

Ba

sin A

vera

ge

Prob

able

Rain

fall

Obj

ectiv

e Im

porta

nt to

estim

ate r

unof

f disc

harg

e for

each

pro

babl

e yea

r.

App

lied

Basin

Av

erag

e Pr

obab

le Ra

infa

ll

Who

le Ba

sin (2

day

s)

・30

yea

rs

392.

3mm

・

100

year

s

445

.8m

m

Type

1: T

ypho

on O

ndoy

Typ

e O

bser

ved

2 da

ys ra

infa

ll x

Enlar

gem

ent R

atio

Esti

mate

d ea

ch 3

4 Th

iesse

n Po

lygo

n 3

Sub

-bas

in A

vera

ge R

ainfa

ll (T

rial b

y WB

Stud

y)

Ret

urn

Perio

dSB

-01

SB-0

2SB

-31

3036

836

939

010

043

944

446

8

Prob

able

2 d

ays

Rai

nfal

l

Ty

pe 2

: Mid

dle-

peak

Fict

iona

l Hye

togr

aph

Esti

mate

d fo

r 3 S

ub-b

asin

s R

etur

nPe

riod

SB-0

1SB

-02

SB-3

130

368

366

382

100

438

441

458

Prob

able

2 d

ays

Rai

nfal

l

Who

le B

asin

(1 d

ay)

・30

yea

rs

232.

4mm

・

100

year

s

285

.5m

m

Evalu

ation

2

days

bas

in av

erag

e pro

babl

e rain

fall

was

estim

ated

bot

h by

JICA

and

WB

Stud

ies. I

n th

is St

udy,

1 da

y ba

sin p

roba

ble r

ainfa

ll is

estim

ated

.

In th

is St

udy,

typh

oon

type

rain

fall

and

mon

soon

type

rain

fall

are

anal

yzed

sep

arate

ly, b

ecau

se th

ese

typh

oon

and

mon

soon

are

diff

eren

t phe

nom

ena

and

it is

unce

rtain

whi

ch

phen

omen

a ca

uses

larg

er fl

oods

. As a

resu

lt of

ana

lysis

, typ

hoon

type

rain

fall

caus

es la

rger

pro

babl

e ra

infa

ll. It

is sa

id th

at ac

cura

cy o

f pro

babl

e an

alysis

is im

prov

ed b

y an

alyzi

ng

rain

fall

with

caus

es.

Floo

d D

ischa

rge

at St

.Nin

o

Obj

ectiv

e D

ischa

rge a

t Sto

.Nin

o is

impo

rtant

to ca

libra

te m

odel

cons

tants

whi

ch is

the k

ey o

f acc

urac

y of

runo

ff m

odel.

Si

nce i

t is d

ifficu

lt of

cont

inuo

us o

bser

vatio

n of

disc

harg

e dire

ctory

, H-Q

equa

tion

to co

nver

t fro

m w

ater l

evel

to d

ischa

rge i

s app

lied.

A

pplie

d Es

timati

on

of F

lood

D

ischa

rge

Ann

ual

high

est

wat

er l

evel

in 1

958-

77,

1986

, an

d 19

94-2

009

wer

e con

verte

d to

disc

harg

e.

H-Q

Equ

ation

:

・Q

= 3

2.03

×( H

-10.

80)2

H

< 1

7.0

・Q

= 1

7.49

× (H

-8.6

1)2

H >

17.

0 H

-Q e

quati

on w

as m

ade

base

d on

obs

erve

d di

scha

rge

and

wat

er le

vel d

ata in

195

8-77

and

1986

. M

ax. d

ischa

rge o

f Typ

hoon

Ond

oy (2

009)

・

3,21

1m3 /se

c

Ann

ual

high

est

wate

r le

vel

in

1958

-77,

19

86,

and

1994

-200

9 w

ere c

onve

rted

to d

ischa

rge.

H-Q

Equ

ation

:

・Q

= 3

1.44

×( H

-10.

96)2

H

> 1

3.0

H

-Q e

quati

on w

as m

ade b

ased

on

obse

rved

disc

harg

e an

d w

ater

lev

el da

ta in

195

8-77

and

198

6, a

nd e

stim

ated

di

scha

rge

by u

nifo

rm f

low

and

obs

erve

d w

ater

lev

el in

19

94-2

009.

M

ax. d

ischa

rge o

f Typ

hoon

Ond

oy (2

009)

・

3,95

0m3 /se

c

Ann

ual h

ighe

st w

ater l

evel

in 1

958-

77, 1

986,

and

1994

-200

9 w

ere c

onve

rted

to d

ischa

rge.

H-Q

Equ

ation

: ・

Q =

32.

03 ×

( H-1

0.80

)2

H <

14.

0 ・

Q =

25.

65 ×

(H-1

0.46

)2

H >

14.

0 H

-Q e

quati

on w

as m

ade

base

d on

obs

erve

d di

scha

rge

and

wat

er l

evel

data

in

1958

-77

and

1986

, an

d es

timat

ed

disc

harg

e by

non

-uni

form

flow

and

obs

erve

d w

ater

leve

l in

1994

-200

9.

Max

. disc

harg

e of T

ypho

on O

ndoy

(200

9)

・3,

480m

3 /sec

Evalu

ation

H

-Q eq

uatio

n by

JICA

Stu

dy w

as b

ased

on

obse

rved

data

, how

ever

, obs

erve

d da

ta du

ring

flood

was

spar

se an

d ac

cura

cy in

hig

h w

ater

leve

l is u

ncer

tain.

H

-Q eq

uatio

n by

WB

Stud

y w

as b

ased

on

obse

rved

and

estim

ated

data

, how

ever

, acc

urac

y of

esti

mat

ed d

ischa

rge i

s low

sinc

e ene

rgy

grad

ient a

nd ro

ughn

ess c

oeffi

cient

appl

ied fo

r

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

85

Item

JIC

A Pr

epar

atory

Stu

dy

WB

Stud

y D

ata C

olle

ction

Sur

vey

(TH

IS S

TUD

Y)

estim

ation

is n

ot p

rope

r.

In th

is St

udy,

non-

unifo

rm fl

ow ca

lcul

ation

is ap

plied

to es

timate

H-Q

equa

tion

in h

igh

wate

r lev

el so

that

accu

racy

in h

igh

wate

r lev

el is

impr

oved

. A

pply

ing

the H

-Q eq

uatio

n es

timat

ed in

this

Stud

y, pe

ak d

ischa

rge a

t Sto

.Nin

o of

Ond

oy T

ypho

on is

estim

ated

as 3

,500

m3/

s. Si

nce a

ccur

acy

of H

-Q eq

uatio

n is

impr

oved

, acc

urac

y of

estim

ated

disc

harg

e is a

lso im

prov

ed.

Runo

ff A

naly

sis

Obj

ectiv

e It

is th

e ana

lysis

to co

nver

t rain

fall

to d

ischa

rge,

and

accu

racy

of a

naly

sis ef

fect

peak

disc

harg

e and

scal

e of s

tora

ge fa

cility

. Ru

noff

Ana

lysis

M

ethod

Rain

fall-

Runo

ff M

odel

Stor

age F

uncti

on M

ethod

: Mou

ntain

ous A

rea

Q

uasil

inier

Sto

rage

Typ

e: U

rban

ized A

rea

Calib

ratio

n an

d Ve

rifica

tion

of M

odel

Para

met

ers

2

flood

s in

2004

was

repr

oduc

ed.

M

odel

para

met

ers

wer

e ca

libra

ted t

o co

nfor

m

calcu

lated

hyd

rogr

aph

to o

bser

ved

disc

harg

e.

Pa

ram

eter

s fo

r St

orag

e Fu

nctio

n M

ethod

(de

lay

facto

rs)

wer

e de

term

ined

ba

sed

on

prev

ious

m

odel.

Inte

grate

d A

naly

sis M

odel

of B

asin

, Ri

ver

and

Floo

d Pl

ains

Ba

sin:

Rain

fall-

Runo

ff M

odel

(S

CS

Uni

t H

ydro

grap

h M

ethod

)

Rive

r: O

ne-d

imen

siona

l Uns

teady

Flo

w M

odel

Fl

ood

Plain

: Tw

o-di

men

siona

l Uns

tead

y Fl

ow M

odel

Calib

ratio

n an

d Ve

rifica

tion

of M

odel

Para

met

ers

Fl

ood

by O

ndoy

Typ

hoon

was

repr

oduc

ed.

M

odel

para

met

ers

wer

e ca

libra

ted

to

conf

orm

ca

lculat

ed h

ydro

grap

h to

obs

erve

d pe

ak d

ischa

rge

and

wat

er le

vel.

Mod

el w

as v

erifi

ed b

y re

prod

ucin

g 20

04 fl

ood

and

1998

floo

d.

Inte

grate

d A

naly

sis m

odel

of b

asin

, riv

er c

ourse

and

flo

od

plain

.

Basin

: Rain

fall-

Runo

ff M

odel

(WEB

-DH

M M

odel)

Rive

r Co

urse

: O

ne-d

imen

siona

l N

on-u

nifo

rm

Flow

M

odel

Fl

ood

Plain

: Tw

o-di

men

siona

l Uns

tead

y Fl

ow A

naly

sis

Mod

el

Ca

libra

tion

and

Verif

icatio

n of

Mod

el Pa

ram

eter

s

Floo

d by

Ond

oy T

ypho

on w

as re

prod

uced

.

Mod

el pa

ram

eter

s w

ere

calib

rated

to

co

nfor

m

calcu

lated

hyd

rogr

aph

to o

bser

ved

hydr

ogra

ph a

s w

ell

as p

eak

disc

harg

e and

wat

er le

vel.

Mod

el w

as v

erifi

ed b

y re

prod

ucin

g 20

04 f

lood

and

20

12 fl

ood.

Evalu

ation

JIC

A St

udy

appl

ied lu

mpe

d sy

stem

mod

el so

that

spati

al va

riatio

n of

rain

fall

coul

d no

t rep

rodu

ced

well

.

WB

Stud

y als

o ap

plied

lum

ped

syste

m m

odel.

To

repr

oduc

e spa

tial v

ariat

ion,

rive

r bas

in w

as se

gmen

talize

d in

to sm

all s

ub-b

asin

s, ho

wev

er, i

t cou

ld n

ot re

prod

uce w

ell.

Th

is St

udy

appl

ies d

istrib

uted

syste

m m

odel

whi

ch c

an re

prod

uce

spati

al va

riatio

n of

rain

fall.

Thi

s mod

el ca

n als

o an

alyz

e lo

ng te

rm ru

noff

so th

at it

can

repr

oduc

e so

il an

d riv

er

cour

se co

nditi

ons b

efor

e flo

od.

In W

B St

udy,

peak

disc

harg

e an

d w

ater l

evel

wer

e co

nfor

med

in th

e ca

libra

tion

of m

odel.

On

the

othe

r han

d, c

alibr

ation

of m

odel

in th

is St

udy

is co

nduc

ted to

con

form

calc

ulate

d hy

drog

raph

to o

bser

ved

hydr

ogra

ph as

well

as p

eak

disc

harg

e and

wate

r lev

el.

Cons

ider

ing

mod

el ch

arac

terist

ics an

d ca

libra

tion

meth

od, f

lood

analy

sis m

odel

in th

is St

udy

is ap

prop

riate

com

parin

g pr

evio

us st

udies

.

Wate

r Lev

el in

La

guna

Lak

e O

bjec

tive

Wate

r lev

el in

Lag

una L

ake e

ffect

disc

harg

e of M

angg

ahan

Flo

odw

ay an

d w

ater l

evel

of M

arik

ina R

iver

ups

tream

of M

angg

ahan

Flo

odw

ay.

A

pplie

d W

ater

Leve

l in

La

guna

La

ke

Aver

age W

ater L

evel

durin

g Fl

ood:

12.

2m

Obs

erve

d W

ater

Lev

el du

ring

Ond

oy T

ypho

on:

12.7

8-13

.85m

Past

Hig

hest

Wate

r Lev

el af

ter M

angg

ahan

Flo

odw

ay

Cons

tructe

d: 1

3.90

m

Evalu

ation

JIC

A St

udy

appl

ied av

erag

e wat

er le

vel d

urin

g flo

od w

hich

is le

ss th

an o

bser

ved

wat

er le

vel d

urin

g O

ndoy

Typ

hoon

.

WB

Stud

y ap

plied

obs

erve

d w

ater l

evel

durin

g Ty

phoo

n O

ndoy

, how

ever

, wat

er le

vel i

n La

guna

Lak

e at

the

mom

ent o

f pea

k w

ater

leve

l of M

arik

ina

Rive

r is l

ess t

han

peak

wat

er

level.

In

this

Stud

y, pa

st m

axim

um w

ater

leve

l is a

pplie

d sin

ce th

ere

is a

case

that

peak

wate

r lev

el in

Lag

una

Lake

occ

ur p

rior t

o pe

ak w

ater

leve

l in

the

river

, and

wate

r lev

el in

Lag

una

Lake

doe

s not

dec

line i

n sh

ort t

ime o

nce r

ise.

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

86

Item

JIC

A Pr

epar

atory

Stu

dy

WB

Stud

y D

ata C

olle

ction

Sur

vey

(TH

IS S

TUD

Y)

Wate

r lev

el in

Lag

una

Lake

effe

ct di

scha

rge

of M

angg

ahan

Flo

odw

ay a

nd it

is n

eces

sary

that

plan

ned

dive

rsion

disc

harg

e is

main

tain

ed a

fter p

eak

wat

er le

vel i

n La

guna

Lak

e. D

iver

sion

volu

me

to M

angg

ahan

Flo

odw

ay is

qui

te im

porta

nt to

floo

d co

ntro

l plan

of P

asig

-Mar

ikin

a Riv

er. C

onsid

erin

g sa

fety

of f

lood

con

trol p

lan, t

he a

pplie

d w

ater

leve

l in

this

Stud

y is

appr

opria

te.

In

unda

tion

Ana

lysis

O

bjec

tive

It is

impo

rtant

for e

valu

ation

of p

lanne

d flo

od co

ntro

l fac

ilitie

s.

App

lied

Inun

datio

n A

naly

sis

Inun

datio

n Ana

lysis

Mod

el

Ri

ver:

One

-dim

ensio

nal U

nstea

dy F

low

Mod

el

Floo

d Pl

ain:

Two-

dim

ensio

nal

Uns

tead

y Fl

ow

Mod

el

Fl

ood

by T

ypho

on O

ndoy

was

repr

oduc

ed.

Si

mul

ation

res

ults

wer

e w

ell c

onfo

rmed

with

in

tervi

ew su

rvey

resu

lts.

Inte

grate

d A

naly

sis M

odel

of B

asin

, Ri

ver

and

Floo

d Pl

ains

Fl

ood

by T

ypho

on O

ndoy

was

repr

oduc

ed.

Si

mul

ation

re

sults

w

ere

wel

l co

nfor

med

w

ith

inun

datio

n m

ap b

ased

on

flood

dam

age s

urve

y.

Inte

grate

d A

naly

sis m

odel

of b

asin

, riv

er c

ourse

and

flo

od

plain

.

Floo

d by

Typ

hoon

Ond

oy w

as re

prod

uced

.

Sim

ulati

on re

sults

wer

e well

conf

orm

ed w

ith in

unda

tion

map

bas

ed o

n flo

od d

amag

e sur

vey.

Evalu

ation

N

ot so

muc

h di

ffere

nce a

mon

g th

e stu

dies

.

Basic

Des

ign

Disc

harg

e W

ithou

t In

unda

tion

Pr

obab

le D

ischa

rge a

t Sto

.Nin

o ・

30 y

ears

2,

740

m3 /se

c ・

100

year

s

3,

210

m3 /se

c

(Not

anal

yzed

) Pr

obab

le D

ischa

rge a

t Sto

.Nin

o ・

30 y

ears

3,

990

m3 /se

c ・

100

year

s

4,

980

m3 /se

c

With

In

unda

tion

(Not

anal

yzed

) Pr

obab

le D

ischa

rge a

t Sto

.Nin

o ・

30 y

ears

3,

600

m3 /se

c ・

100

year

s

4,

100

m3 /se

c La

rge

scale

inun

datio

n at

left

side

betw

een

conf

luen

ce o

f N

angk

a Riv

er an

d Ro

sario

Weir

by

dyke

bre

ak

・30

yea

rs

3,03

0 m

3 /sec

・10

0 ye

ars

3,58

0 m

3 /sec

Floo

d D

ischa

rge

Allo

catio

nDes

ign

30 y

ears

Pr

evio

us d

ischa

rge a

lloca

tion

is ap

plied

.

Coun

term

easu

res a

gain

st 30

yea

r pro

babl

e flo

od:

・Ri

ver I

mpr

ovem

ent

・M

CGS

(Not

impl

emen

ted in

Pha

se II

I) 30

yea

rs pr

obab

le di

scha

rge (

with

MCG

S)

Secti

on

Q(m

3/s)

Waw

a 1,

590

(Non

e)

The f

ollo

win

g co

unter

mea

sure

are r

ecom

men

ded.

Co

unter

mea

sure

s aga

inst

30 y

ear p

roba

ble f

lood

: A

ltern

ative

-A;

・Ri

ver I

mpr

ovem

ent

・M

CGS

・Im

prov

emen

t of

Man

ggah

an F

lood

way

A

ltern

ative

-B;

・Ri

ver I

mpr

ovem

ent

・M

CGS

・Co

nstru

ction

of R

etard

ing

Basin

30

yea

rs pr

obab

le di

scha

rge (

with

MCG

S)

uni

t: Q

(m3 /s)

Secti

on

Alt-

A

Alt-

B W

awa

2,72

0 2,

720

The

Rep

ublic

of

the

Phili

ppin

es

Dat

a C

olle

ctio

n Su

rvey

on

Floo

d M

anag

emen

t in

Met

ro M

anila

Fina

l R

epor

t 4-

87

Item

JIC

A Pr

epar

atory

Stu

dy

WB

Stud

y D

ata C

olle

ction

Sur

vey

(TH

IS S

TUD

Y)

Rodo

riges

Brid

ge

2,11

0 Be

fore

Nan

gka R

iver

2,

420

St. N

ino

2,90

0 M

anga

han

Floo

dway

2,

400

Low

er M

arik

ina R

iver

50

0 N

apin

dan

Chan

nel

0 Pa

sig R

iver

60

5 Sa

nJua

n Ri

ver

700

Pasig

Riv

er –

Man

ila B

ay

1,20

0

Mon

talba

n Br

idge

3,

560

3,56

0 (R

etard

ing

Basin

)

St

. Nin

o 3,

100

2,90

0 M

anga

han

Floo

dway

2,

600

2,40

0 Lo

wer

Mar

ikin

a Riv

er

500

500

Nap

inda

n Ch

anne

l 0

0 Pa

sig R

iver

60

0 60

0 Sa

nJua

n Ri

ver

700

700

Pasig

Riv

er –

Man

ila B

ay

1,30

0 1,

300

100

year

s (N

one)

Alte

rnati

ve

2 in

cludi

ng

the

follo

win

g m

easu

res

is re

com

men

ded.

Co

unter

mea

sure

s aga

inst

100

year

pro

babl

e flo

od:

・Ri

ver I

mpr

ovem

ent

・M

arik

ina D

am

・Re

tardi

ng B

asin

・

Non

-stru

ctura

l Mea

sure

s 10

0 ye

ars p

roba

ble d

ischa

rge (

with

out M

CGS)

Se

ction

Q

(m3/

s) W

awa

3,60

0 M

arik

ina D

am

900

Mon

talba

n Br

idge

2,

400

(Reta

rdin

g Ba

sin)

St

. Nin

o 2,

900

Man

gaha

n Fl

oodw

ay

2,00

0 Lo

wer

Mar

ikin

a Riv

er

1,00

0 N

apin

dan

Chan

nel

600

Pasig

Riv

er

850

SanJ

uan

Rive

r 1,

000

Pasig

Riv

er –

Man

ila B

ay

1,80

0

Alte

rnati

ve A

-2-1

and

B-3

are s

how

n in

belo

w.

Coun

term

easu

res a

gain

st 10

0 ye

ar p

roba

ble f

lood

: A

lerna

tive-

A-2

-1;

・Ri

ver I

mpr

ovem

ent

・M

CGS

・Im

prov

emen

t of

Man

ggah

an F

lood

way

・

Mar

ikin

a Dam

A

lerna

tive-

B-3;

・

Rive

r Im

prov

emen

t ・

MCG

S ・

Mar

ikin

a Dam

・

Retar

ding

Bas

in

100

year

s pro

babl

e disc

harg

e (w

ith M

CGS)

u

nit:(

m3 /s)

Secti

on

A-2

-1

B-3

Waw

a 3,

230

3,23

0 M

arik

ina D

am

1.26

0 1.

260

Mon

talba

n Br

idge

2,

140

2,50

0 (R

etard

ing

Basin

)

St

. Nin

o 3,

100

2,90

0 M

anga

han

Floo

dway

2,

400

2,40

0 Lo

wer

Mar

ikin

a Riv

er

500

500

Nap

inda

n Ch

anne

l 0

0 Pa

sig R

iver

60

0 60

0 Sa

nJua

n Ri

ver

780

780

Pasig

Riv

er –

Man

ila B

ay

1,40

0 1,

400

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