“v”, “l”, and “s” canals churchill county, nevada

Breach Inundation Analysis

USBR Newlands Project

“V”, “L”, and “S” Canals Churchill County, Nevada

January 2013

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TABLE OF CONTENTS

1. Purpose…………………………………………………………………………………………………. 5 2. Study Area…………………………………………………………………………………………….. 5 3. Project Datum……….……………………………………………………………………………... 6 4. Topographic and Geometric Data…………………………………………………………. 6 5. Hydrologic Data……………………………………………………………………………………. 7 6. Embankment Failure Scenarios…………………………………………………………….. 8 7. Inline Check-Structure Failure Scenarios……………………………………………….. 8 8. Canal System Hydraulic Modeling………………………….…………………………….. 8

8.1 Base HEC-RAS Model……………………………………………………………………… 9 8.2 Canal Embankment Failure Models…………….…………………………………. 12 8.3 Inline Structure Failure Models………………….…………………………………… 12

9. Two Dimensional Floodplain Mapping…………………………………………………. 13 9.1 FLO-2D Model……………………………………………………………………………….. 13

10. Sensitivity Analysis………………………………………………………………………………. 15 8.1 HEC-RAS Sensitivity……………………………………………………………………….. 15 8.2 FLO-2D Sensitivity………………………………………………………………………….. 15

11. Results…………………………………………………………………………………………………… 16 12. List of References………………………………………………………………………………….. 18

Appendix A Result Plates

Appendix B Quality Control Certification

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TABLES

Table 4-1 Inline check structures Table 4-2 Bridges Table 5-1 Estimated Canal Flow Rate Table 9-1 FLO2D Inflow Grid Location Table 9-2 Roughness Coefficients Table 7-1 Results Summary

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PLATES

PLATE 1 General Map PLATE 2 Study Area PLATE 3 FLO-2D Topography PLATE 4 Water Surface Profile – V Canal PLATE 5 Water Surface Profile – L Canal PLATE 6 Water Surface Profile – S Canal PLATE 7 Levee Breach V Canal – Depth of Inundation PLATE 8 Levee Breach V Canal – Time to One Foot Inundation PLATE 9 Levee Breach V Canal – Velocity of Floodwater PLATE 10 Levee Breach L Canal #1 – Depth of Inundation PLATE 11 Levee Breach L Canal #1 – Time to One Foot Inundation PLATE 12 Levee Breach L Canal #1 – Velocity of Floodwater PLATE 13 Levee Breach L Canal #2 – Depth of Inundation PLATE 14 Levee Breach L Canal #2 – Time to One Foot Inundation PLATE 15 Levee Breach L Canal #2 – Velocity of Floodwater PLATE 16 Levee Breach S Canal #1 – Depth of Inundation PLATE 17 Levee Breach S Canal #1 – Time to One Foot Inundation PLATE 18 Levee Breach S Canal #1 – Velocity of Floodwater PLATE 19 Levee Breach S Canal #2 – Depth of Inundation PLATE 20 Levee Breach S Canal #2 – Time to One Foot Inundation PLATE 21 Levee Breach S Canal #2 – Velocity of Floodwater PLATE 22 Inline Check Structure Failure VC3 – Depth of Inundation PLATE 23 Inline Check Structure Failure VC3 – Time to One Foot Inundation PLATE 24 Inline Check Structure Failure VC3 – Velocity of Floodwater PLATE 25 Inline Check Structure Failure VC6 – Depth of Inundation PLATE 26 Inline Check Structure Failure VC6 – Time to One Foot Inundation PLATE 27 Inline Check Structure Failure VC6 – Velocity of Floodwater PLATE 28 Inline Check Structure Failure LC1 – Depth of Inundation PLATE 29 Inline Check Structure Failure LC1 – Time to One Foot Inundation PLATE 30 Inline Check Structure Failure LC1 – Velocity of Floodwater PLATE 31 Typical V Canal Cross Section PLATE 32 Typical L Canal Cross Section PLATE 33 Typical S Canal Cross Section PLATE 34 Fernley, NV Breach Location PLATE 35 Fernley Breach Pictures #1 PLATE 36 Fernley Breach Pictures #2 PLATE 37 Water Surface Profile, Sensitivity Analysis – V Canal PLATE 38 Water Surface Profile, Sensitivity Analysis – L Canal PLATE 39 Water Surface Profile, Sensitivity Analysis – S Canal

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1. Purpose The purpose of this study is to assist Churchill County in the evaluation of flood consequences relative to hypothetical beach scenarios of the Bureau of Reclamation Newland Irrigation project’s “V”, “S”, and “L” canals. Inundation maps were developed for 5 levee embankment and 3 inline check structure failure scenarios. The probability of each hypothetical scenario occurring was not evaluated. It is anticipated this flood consequence information will be used by Churchill County to evaluate emergency evacuation routes and manage future development. A general map of the study area is provided as Plate 1. The analysis is limited to the “V”,”S” and “L” canals within the study area. Failure of lateral canals were not included since they have significantly lower flow capacity and probability of failure was estimated to be insignificant. Inundation from flood flows on the Carson River was not included in the analysis and the limit of the study area was defined as the FEMA 1% Annual Chance of Exceedance floodplain for the Carson River.

2. Study Area The study area is located within Churchill County, Nevada. The study area is subject to potential flooding if a breach were to occur in the embankments of the “V”, “S”, and “L” canals of the U.S. Bureau of Reclamation’s Newland Irrigation Project. A map of the study area is provided as Plate 2. A map of the topography of the study area is shown in Plate 3. The U.S. Bureau of Reclamation’s Newland Irrigation Project provides irrigation water from the Truckee and Carson Rivers to about 55,000 acres of cropland in the Lahontan Valley near Fallon and bench lands near Fernley in western Nevada (USBR, 2012). Water for the Newlands Project is diverted from the Truckee River into the Truckee Canal for irrigation of the Truckee Division and for conveyance to Lahontan Reservoir for storage. Water stored in Lahontan Reservoir or conveyed by the Truckee Canal is released into the Carson River either directly or through the Lahontan Powerplant. Water is then diverted from the Carson River into the `V` and `T` Canals at Carson Diversion Dam for irrigation of the Carson Division. The “T” canal runs north of the Carson River approximately 9 miles and is located outside the study area. The capacity of the “T” canal is 450 cfs and has a bottom width of 10 feet. The “V” canal runs south of Carson River approximately 27 miles and provides irrigation water to the study area. The capacity of the “V” canal is 1,500 cfs and has a bottom width of 22 feet and 2:1 side slope. Within the study area, the “V” canal splits into the “S” and “L” canals which have no published capacity. The “S” and “L” bottom widths were surveyed during this study and estimated to be 50 feet and 35 feet respectively. Inline check structures along the canal are used manage stages and divert flows to lateral sub-canals and irrigation fields.

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Within the study area the “V”, “S”, and “L” canals are perched above adjacent land and flows are contained by levee embankments. Significant flooding and economic loss could occur if an embankment or check structure failure resulted in a rapid release of canal water. Flood risk from canal failure was recognized after recent failures on the Newland Project’s canal system. A January 2007 levee breach on the Newland Project’s Truckee-Carson canal caused extensive flooding in Fernley, Nevada. Pictures of the 2007 Truckee-Carson canal failure are provided in Plate 34-36. The Lewis Spillway structure on the “V” canal failed in June 2008 sending a flood wave down a creek but resulted in no urban damages.

3. Project Datum All elevations presented herein are based on NAVD88 vertical datum. All horizontal data presented herein are based on NAD83 horizontal datum and Nevada West State Plain horizontal projection. All elevations and horizontal coordinates are in units of in U.S. survey feet.

4. Topographic and Geometric Data The topographic data used for this modeling effort was based on Light detection and ranging (LIDAR) data. LIDAR was flown by Sanborn to capture the land of Churchill County and surrounding area (553 square miles) between March 29 and June 17, 2011. The LIDAR mapping was specified to support a contour interval of 1 foot and vertical accuracy of 0.5’ RMSE. Further details of the LIDAR survey conducted for this study are given in the report titled “LiDAR Campaign (Churchill County, NV) Report of Survey” (Reference 1). The data source was in NAVD88 vertical datum and NAD83 horizontal datum, project in Nevada West State Plane in U.S. survey feet. Bridge and inline check structure surveys were conducted by GA Engineering, Planning and Land Surveying Inc. of Reno Nevada. The surveys were conducted for bridges and structures on the V, S, and L canals around Fallon, Nevada. The bridges and inline check structure surveys were completed between November 12, 2010 and March 3, 2011 in survey-grade detail and are given in Table 3.1 and 3.2. Surveys were conducted in NAVD88 vertical datum and NAD83 horizontal datum.

Table 4-1 - Inline Check Structures Canal Structure

V Canal VC1 - 26 Foot Drop Structure V Canal VC2 V Canal VC3 V Canal VC4 V Canal VC5 V Canal VC6 V Canal VC7 V Canal VC8 S Canal SC1

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L Canal LC1 L Canal LC2 L Canal LC3

Canal BridgeV Canal Sheckler Bridge (VB4)V Canal Strasdin Bridge (VB5)V Canal McLean Bridge (VB6)V Canal Highway 50 & Williams Bridge (VB7) V Canal Railroad Trussel Bridge (VB8)S Canal Venuracci Bridge (SB2)S Canal Coleman & HWY 95 Bridge (SB3)S Canal Paiute Bridge (SB4)S Canal Rio Vista Bridge (SB5)L Canal Casey Road Bridge (LB1)L Canal Lattin Bridge (LB2)L Canal Allen Road Bridge (LB4)L Canal High School Road Bridge (LB5)L Canal Schurz Highway Bridge (LB6)L Canal Maine Street Bridge (LB7)L Canal Harrigan Bridge (LB8)

Table 4-2 - Bridges

5. Hydrologic Data Flow rates in the “V”, “S” and “L” canals are regulated by the Carson River Diversion Dam. Since the canals are manmade and flows are regulated, a natural flow hydrologic flood frequency analysis is not applicable. The Truckee Carson Irrigation District (TCID) has some gage data for recorded flows within the “V”, S, and “L” canals. However, this information was considered unreliable due to unmeasured losses in the system. These losses include percolation, water transferred to and from lateral canals, and direct pumping from the canal at differing locations. Normal operating flows within the “V”, S, and “L” canals were estimated for this study by varying the flow rate of the hydraulic model (model described below) to match a measured water surface profile. The water surface profile was surveyed by Churchill County on 12/23/2010 while the canal system was flowing at full capacity. Plates 4 through 6 shows computed water surface profiles and measured water surface elevations for the “V”, “S” and “L” canals. The resulting flow rates are provided in table 5.1. The flow rates include a lateral canal transfer of 40 cfs from the Carson River into the “S” Canal. The flow enters the “S” canal just upstream of Repogle Weir at station 14500.

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Table 5-1 - Estimated Canal Flow Rate Canal Reach Flow (cfs)

V Canal 275 S Canal (Station 27317.3 to 14500.7) 118

S Canal 158 L Canal 157

6. Embankment Failure Scenarios

Flood inundation initiated by a levee embankment piping failure followed by canal breach was evaluated. Simulations were conducted independently at the five locations shown in Plate 2. One canal breach was simulated on the “V” canal, two canal breaches are on the “S” canal and two locations are on the “L” canal. The location for each breach simulation was determined with input from Churchill County Engineering Department. The locations are intended to demonstrate the range of consequences from hypothetical breach locations within the study area. The locations are based on the canal location relative to topographic features, urban density, and relative distance to critical infrastructure. Breach failure characteristics were based data collected by Churchill County, from the 2007 levee failure at Fernley, NV. The breach was within the same system and the canals were constructed in a similar fashion, Plates 35 and 36 show pictures of the breach and the immediate inundated area. A detailed geotechnical investigation was not conducted for this study. The levee embankments were constructed in 1903 and design standards are unknown. The levees were assumed to be constructed from local borrow soils which are primarily silty sands. The assumptions for all breach scenarios are as follows:

• Only one breach is simulated per scenario. • Failure is initiated by piping.

• Time to complete failure would take 10 minutes. • At full development, the width of breach equals two times the width of the canal at

the breach location.

• At full development the levee breach extends from top of levee to the landside toe with breach side slopes of zero.

7. Inline Check-Structure Failure Scenarios Flood inundation initiated by an upstream inline structure failure was also evaluated. Check structures are used to maintain water levels along the canal over a range of flow. The check structures act like small dams or drop structures and impound water in the upstream reach.

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Failure of a check structure would rapidly release the impounded water into the downstream reach and could exceed the canal capacity causing an overtopping or piping failure. The Sacramento District - Dam Safety Section, with assistance from Churchill Country Engineering, performed a hazard assessment1 of the study area to determine areas of potential failure. Churchill County identified three inline check structures to analyze for potential failure, VC-3, VC-6 and LC-1 (shown in Plate 2). The assumptions for all inline check structure failure scenarios are as follows:

• The entire inline check-structure would fail. Partial failure was not assumed.

• A complete failure would occur over 6 minutes. • The failure mode would be similar to piping.

• No repairs to structure that failed during the simulation. • After an inline structure fails, it is assumed levee embankments downstream of the

check structure will also fail if the water surface elevation is a half a foot (or less) from the top of levee for more than 24 minutes. The levee embankment failure assumptions are the same as described in Section 6.

8. Canal System Hydraulic Model

A one-dimensional unsteady hydraulic model, HEC-RAS (version 4.1.0), was used to model the canal system within the study area and develop breach hydrographs for 5 levee breach scenarios and 3 inline check structure failure scenarios. The breach scenario models were developed from a base model that represents the canals operating at full capacity (with no failures). Stages and flows in this base model were calibrated to water surface profiles measured by Churchill County Engineering on 12/23/2010. 8.1 Base Model

a) Geometry Cross sections were generated using Geo-RAS from LIDAR provided by Churchill County. Model cross section spacing varies based on required accuracy. From Carson Division Dam (XS 26800) to just upstream of the “26 foot drop” structure (XS 24489.45), a cross section spacing of roughly 1,500 feet apart was used on the “V” canal. This portion of the reach was included only for routing purpose and no failure analysis has been performed for this portion of the reach. For all other model reaches the cross section spacing varies from 200 to 400 feet apart. Typical cross sections for each respective canal can be found on Plates 31 to 33.

b) Storage Areas and Storage Area Connections

1 SPK – Dam Safety Section - Qualitative Hazard Assessment – Inline Check Structures, Truckee-Carson Irrigation District, Churchill County, NV (July 2011)

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Storage areas and storage area connections were also generated through Geo-RAS from LIDAR provided by Churchill County. The storage areas and storage area connections model the water leaving the canal system within the study area.

c) Lateral Structures Levee embankments were modeled as a series of lateral structures in HEC-RAS. The lateral structures were drawn along the crest of the levees. Levee embankment crest elevations were obtained from the LIDAR data using Geo-RAS. The levees were then connected to the Storage Areas to allow the flow to leave the channel and flow into the overland areas.

d) Upstream Boundary Conditions HEC-RAS Model cross section 26800 along the V Canal represents the upstream boundary condition. Inflow to the model was estimated as a steady flow hydrograph of 275 cfs which reflects the normal operating flow.

e) Internal Boundary Conditions. The model includes a lateral canal transfer of 40 cfs from the Carson River into the “S” Canal. The flow enters the “S” canal just upstream of Repogle Weir at station 14500.

f) Downstream Boundary Conditions The downstream boundary condition for the both “S” canal (XS 50.12576) and the “L” canal (XS 74.39626) were rating curves developed from the measured stages and estimated flows. The rating curves assume the downstream weir type check structure will maintain a relatively consistent stage over a full range of flow. The exception was for the “V” Canal Inline Check Structure Breach run (VC1), which used normal depth as the downstream boundary condition. This was due to instability in the model to converge on a solution. The V Canal is far enough upstream from the location of the boundary condition that normal depth will not affect the solution.

g) Manning’s roughness Coefficient The “V”, “S” and “L” canals are all earthen channels (primarily sand) that are relatively uniform and straight. It is assumed the Truckee Carson Irrigation District (TCID) maintains the canals and prevents vegetation growth within the canals. Since all canals display the same characteristics, a roughness of 0.022 was selected for all portions of the canals. The Manning’s roughness coefficient was estimated from Chow’s Open-Channel Hydraulics handbook2 After analysis was complete Churchill County mentioned that in summer months some vegetation grows on the outer banks of the canals. The Manning’s roughness coefficient

2 Chow, V.T. – Open-Channel Hydraulics (pg. 119 Figure 5.5-11)

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was estimated from Chow’s Open-Channel Hydraulics handbook3 and determined to be closer to 0.026 for the summer months. The sensitivity analysis (Section 8.1, a) showed change in roughness to the outer banks would not significantly impact the results.

h) Bridges/Inline Structures Bridges and inline structures within the modeled canal reaches were included. The inline structure surveys identify each gate’s width, height and concrete invert. Wood slats can be inserted into the gates to raise the invert and some gate openings can be adjusted by mechanical gates. Churchill County advised that the gate configurations are rarely changed and the pictures taken during the survey represent each structure’s typical gate configuration. Based on these pictures each gate’s invert and height of opening were estimated. Churchill County conducted a survey of the typical water surface when the V, S and L canals are at full capacity. To validate the model to match these survey water surface elevations some of the gate configurations were slightly altered. Since the inline structure surveys only included invert elevations of concrete gates and did not account for wood slates in place, the invert elevation was estimated. These estimates were altered until the model water surface profile matched the surveyed elevations. No floating debris was included on any of the bridge piers. There is an existing debris removal system at the upstream most check structure (26 Foot Drop) that is assumed to remove most debris from the canal system.

i) Bank Stations Bank stations are estimated using the water surface elevation of the canals while at full capacity.

j) Obstructed Areas Obstructed areas were used for areas right of the right levee and left of the left levee to prevent the HEC-RAS model from erroneously using that area as conveyance.

k) Expansion/Contraction Coefficients All cross sections upstream and downstream of bridges were assigned an expansion coefficient of 0.3 and a contraction coefficient of 0.1. Cross sections upstream and downstream of inline structures were assigned expansion and contraction coefficients of 0.5 and 0.3, respectively. All other cross sections have an expansion and contraction coefficient of zero.

3 Chow, V.T. – Open-Channel Hydraulics (pg. 119 Figure 5.5-11)

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8.2 Canal Embankment Failure Models Flood inundation was simulated for scenarios in which the canal breach was initiated by a levee embankment failure. Model simulations were conducted independently at the five locations shown in Plate 2. The model assumptions for all canal breach scenarios are as follows:

• Only one breach is simulated per model plan.

• Failure mode is piping. • Time to complete failure would take 10 minutes.

• At full development, the width of breach equals two times the width of the canal at the breach location.

• At full development the levee breach extends from top of levee to the landside toe with breach side slopes of zero.

• Assume there are only flows in the V, S and L canals. Except for the inflow from the Carson River into the S canal at cross section 14500, there are no water transfers with smaller lateral canals.

• At time of failure, the V, S and L canals are at full capacity described in Table 3-1. • After a failure occurs the Carson River Diversion Dam is the only check structure

closed in response to a failure. Based on estimated response time, the check structure is closed 6 hours after the failure.

8.3 Inline Structure Failure Models Flood inundation was simulated for scenarios in which the canal breach was initiated by overtopping from an upstream inline structure failure. The assumptions for all inline check structure failure models are as follows:

• Fail the whole inline structure (not portion)

• Time to complete failure: 6 minutes • Failure mode is piping

• After an inline structure fails, it is assumed levees downstream of the check structure will also fail if the water surface elevation is a half a foot (or less) from the top of levee for more than 24 minutes. The levee failure assumptions are the same as described in Section 8.2.

• Assume there are only flows in the V, S and L canals. Except for the inflow from the Carson River into the S canal at cross section 14500, there are no water transfers with smaller lateral canals.

• At time of failure, the V, S and L canals are at full capacity described in Table 3-1.

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• After a failure occurs the Carson River Diversion Dam is the only check structure closed in response to a failure. Based on estimated response time, the check structure is closed 6 hours after the failure.

9. Two Dimensional Floodplain Mapping A two dimensional model, FLO-2D (version 2009.06, build no. 09-11.07.06) was used to develop inundation maps for each of the failure scenarios. Results from the HEC-RAS model are used as inputs into the FLO-2D model. 9.1 FLO-2D Model

a) Grid Element Development The computational grid size for the model is 100 x 100 feet. This was determined to be the optimal grid size based on peak flows, level of inundation mapping detail and model run time. LIDAR (described in Section 3) was used to develop elevation points for each grid element in the FLO-2D model. The elevation data was too dense for the FLO-2D preprocessing program. ARCGIS was used to resample the data using a nearest neighbor algorithm to a 25 x 25 foot grid. The computation grid was developed by averaging the elevation points using the standard deviation difference to filter the grid element elevations. The topography within the FLO-2D boundary is shown in Plate 6.

b) Inflow nodes Breach hydrographs (water leaving the canal) from the HEC-RAS results were used for flow inputs into the FLO2D model. Inflow nodes are placed in the grid element at the location of failure. A 10-minute hydrograph increment was found to represent the breach hydrograph in sufficient detail. Inflow grid elements for each breach location are described in Table 9.1.

Table 9-1 – FLO2D Inflow Grid Element Location

Breach Location grid element number Levee Breach - V Canal 40362 Levee Breach - L Canal #1 49297 Levee Breach - L Canal #2 54833 Levee Breach - S Canal #1 15719 Levee Breach - S Canal #2 21895 Inline Check Structure Failure - VC3 51171 & 8387 Inline Check Structure Failure - VC6 36183 & 29672 Inline Check Structure Failure - LC1 55329

c) Outflow nodes Outflow nodes were placed at grid cells along the boundary of the FLO-2D model. Since the model boundaries were chosen to capture flooding in populous areas, minimal flooding in agricultural areas outside the model extents is not considered significant. For

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model stability, outflow nodes were placed at locations where minimal flows reach the model boundary.

d) Manning’s “n” values Roughness values were assigned using aerial photography. Since these are roughness values that represent relatively shallow flow, they are higher than the roughness used to represent the channel. Typical roughness values are based on FLO2D’s recommended Manning’s “n” roughness values and are described in Table 9-2.

Table 9-2 - Roughness Coefficients

Land Use Manning's n value Residential 0.11 Park Areas 0.065 Commercial 0.11

Rural/Agriculture 0.09 Default Floodplain

Value 0.09

e) Width Reduction Factors In FLO-2D width reduction factors and area reduction factors can be used to represent obstructions in the study area (i.e. a neighborhood of houses). Width reduction factors reduce the width of conveyance in each element. Three areas in the model were assigned width reduction factors. Dense commercial areas were assigned a value of 0.9, Downtown/dense residential areas were assigned a value of 0.3 and light residential was assigned a value of 0.1.

f) Area Reduction Factors Area reduction factors were not used in this modeling effort. The area reduction option in FLO-2D reduces the storage volume of a grid element. There were no areas within the model that required reduced storage volume.

g) Floodplain infiltration The infiltration option was not used in the FLO-2D model.

h) Levees and Embankments Levees and embankments were included only in areas where it would affect the inundation mapping results. It is time intensive to add levee details in each grid cell, so aerial photos and preliminary inundation maps were used to determine locations where levee details were needed to simulate the inundation. If this model were to be used for

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other purposes, additional levee information may need to be coded into the mode to represent the hydraulic conditions.

10. Sensitivity Analysis A sensitivity analysis of major hydraulic model assumptions was conducted. Sensitivity analysis was performed by altering the assumption and comparing to the results of the final adopted condition. 10.1 HEC-RAS Sensitivity

a) Roughness Coefficient Manning’s n values were increased and decreased by 20%. The base model with no breaches was used to create two new plans; one with Manning’s n value of 0.0264 and the other with roughness of 0.0176. The water surface profiles were compared against each other, as shown in Plates 31-33. The V canal was not sensitive to the changes in roughness values, while the variation on roughness did seem to have a slight impact on the S and L canals. The largest difference in water surface profiles for the S and L canals typically occurred downstream of inline check structures. At locations downstream of check structures, the largest difference in water surface elevation on the S canal was 0.48 feet and 0.22 feet on the L canal.

b) Breach Parameters

Another major assumption that could impact the results is the breach parameters. Of all the breach parameter inputs, the one that could most significantly change the breach hydrograph is the breach width. In the adopted condition for final analysis it was assumed the breach width was equal to twice the width of the canal. A breach width equal to the width of the canal was used for the sensitivity analysis. The VC-6 inline check structure failure scenario was used to compare the breach hydrographs with the two varying breach widths. The sensitivity run with breach widths equal to the canal widths, created smaller breach hydrographs with 29% less volume (left bank failure) and 15.6% less volume (right bank failure) than the run with breaches equal to twice the canal widths.

10.2 FLO-2D Sensitivity The roughness values in FLO-2D were increased by 20%. The resulting roughness for park areas have a roughness of 0.078, residential and commercial have a roughness of 0.132 and rural/agricultural and the default floodplain value have a roughness of 0.108.

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Increasing the roughness values caused a decrease in floodplain velocity up to 3 feet per second within the study limit. The water surface elevation varied ±0.5 feet in the majority of the grid elements.

11. Mapping and Results The inundation maps indicate flood consequences within the study area from breach failures on V, S and L canals. The maps do not address flood hazard from the Carson River, its tributaries, or any other irrigational canals. The flooding scenarios are based on the canals at full capacity. Inundation from flood flows on the Carson River was not included in the analysis and the limit of the study area was defined as the FEMA 1% Annual Chance of Exceedance floodplain for the Carson River. Results are described in maps showing maximum depth of inundation (Flow Depth at Cell.shp), maximum velocity (Velocity at Cell.shp) and time from breach to 1 foot of flood depth (Time for One Foot.shp) at each grid cell. The depth of inundation ranged from 0 to 4 feet with the velocity of the flow lower than 1 foot/sec. Flow Depth results show what the maximum depth (feet) in an individual FLO2D cell regardless of the time step it achieved the maximum depth. Time (hr) to 1 foot of depth shows the time from the initial levee breach (either through overtopping or levee breaching) till an individual FLO2D cell to reach 1 foot of depth. The maximum velocity results (ft/s) are the maximum velocity the flow reaches within any given cell. Table 11-1 shows the total number of acres inundated (for depths greater than 0.1ft) and the corresponding, depth of inundation, time to one foot inundation and velocity maps for each failure scenario.

Table 11-1 – Results Summary

Failure Scenario Acres

Inundated** Depth of

Inundation Time to 1 Foot

Inundation Velocity Levee Breach - V Canal 304.87 PLATE 7 PLATE 8 PLATE 9 Levee Breach - L Canal #1 304.64 PLATE 10 PLATE 11 PLATE 12 Levee Breach - L Canal #2 310.84 PLATE 13 PLATE 14 PLATE 15 Levee Breach - S Canal #1 574.61 PLATE 16 PLATE 17 PLATE 18 Levee Breach - S Canal #2 577.82 PLATE 19 PLATE 20 PLATE 21 Inline Check Structure Failure - VC3 773.88 PLATE 22 PLATE 23 PLATE 24 Inline Check Structure Failure - VC6 1750.92 PLATE 25 PLATE 26 PLATE 27 Inline Check Structure Failure - LC1 478.42 PLATE 28 PLATE 29 PLATE 30

**Surface area of inundation regardless of the time of occurrence (for flow depths greater than the "TOL" value typically 0.1ft)

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The inundation maps for the inline check structure failures are not at the location of the failed check structure. The volume of water behind the check structures was not big enough to overwhelm the downstream canals and overtop the levees; instead, after a check structure failure, a floodwave would travel down the canals and pass through the study area with no flooding. Because of this, it was assumed (as documented in Section 5.3) that if the water surface elevation is within 0.5 feet of the top of levee for more than 24 minutes, a levee failure would occur. For some of the check structure failures, this occurred miles downstream of the check structure failure location.

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12. References

Chow, V. T. (1959). Open-Channel Hydraulics. The Blackburn Press.

GA Engineering, Planning and Land Surveying Inc., Churchill Country Flood Hazard Study and Modeling “V” Line, “S” Line and “L” Canals Sheet Drawings: 2010.

O’Brien, J. (2009)FLO-2D Pocket Guide. Version 2009.06.

Stojicevic, M. M. (2008). Capital Projects and Engineering Manager. Fernley Nevada Levee Breach 2008 Power Point Presentation.

U.S. Department of the Army – Hydrologic Engineering Center (January 2010). HEC-RAS River Analysis System User’s Manual. Retrieved from http://www.hec.usace.army.mil/software/hec-ras/documents/HEC-RAS_4.1_Users_Manual.pdf

U.S. Department of the Army – Hydrologic Engineering Center (January 2010). HEC-RAS River Analysis System Hydraulic Reference Manual. Retrieved from http://www.hec.usace.army.mil/software/hec-ras/documents/HEC-RAS_4.1_Reference_Manual.pdf

U.S. Department of the Interior – Bureau of Reclamation (May 11, 2011). Project Details - Newlands Project, Retrieved from http://www.usbr.gov/projects/Project.jsp?proj_Name=Newlands+Project

http://www.hec.usace.army.mil/software/hec-ras/documents/HEC-RAS_4.1_Users_Manual.pdf

http://www.hec.usace.army.mil/software/hec-ras/documents/HEC-RAS_4.1_Users_Manual.pdf

http://www.hec.usace.army.mil/software/hec-ras/documents/HEC-RAS_4.1_Reference_Manual.pdf

http://www.hec.usace.army.mil/software/hec-ras/documents/HEC-RAS_4.1_Reference_Manual.pdf

http://www.usbr.gov/projects/Project.jsp?proj_Name=Newlands+Project

APPENDIX A

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U.S. ARMY CORPS OF ENGINEERSSACRAMENTO DISTRICT

GENERAL MAP

BREACH INUNDATION ANALYSIS"V", "L", and "S" CANALS

CHURCHILL COUNTY, NEVADA

SEP 2012

!"c$

I½

LegendCarson River

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal

Interstate

Highway

Primary Road

Railroad

County Boundary

Study LocationStudy Location´

Elevation in Feet4,400 to 4,600

4,600 to 4,800

4,800 to 5,000

5,000 to 5,400

5,400 to 5,800

below 3,900

3,900 to 4,000

4,000 to 4,100

4,100 to 4,200

4,200 to 4,300

4,300 to 4,400

!(")

")

")

XXW

XXWXXW

XXWXXW

CCaarr ssoo nn RR ii vv ee rr

SodaLake

ShecklerReservoir

Fallon NavalAir Station

FallonMunicipal

Airport S LineReservoir

Drumm Ln

Union Ln

N A

llen

Rd

Har

rigan

Rd

Pas

tur e

Rd

f low

f lowRattlesnakeHill

S-Canal #2S-Canal #1

L-Canal #2L-Canal #1

V-Canal #1 LC1VC6

VC3

£¤95

£¤50

FallonC H U R C H I L LC H U R C H I L L

C O U N T YC O U N T Y

0 1 2Miles



STUDY AREA



SEP 2012

LegendT-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal

Limit of Mapping*

XXW Modeled Levee Failure

") Modeled Structure Failure

Highway

Major Road

Railroad

´

Background Imagery: Bing Maps Aerial

*The boundary is defined by the probability of flooding from the V, S, and L canals.It does not include probability of flooding from the Carson River or other irrigation canals.

!(")

")

")

XXW

XXWXXW

XXWXXW

CCaarrssoo nn RRii vvee

rr

SodaLake

ShecklerReservoir


FallonMunicipal

AirportS LineReservoir

Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Past

ure

Rd

RattlesnakeHill

f low

f low

TT-- LL ii nnee CCaannaall

SS--LL iinnee CCaannaall

LL--LLiinnee CCaannaa ll

VV--LLiinnee CCaannaall S-Canal #2S-Canal #1

L-Canal #2L-Canal #1

V-Canal #1 LC1

VC6VC3

£¤95

£¤50

Fallon

0 1 2Miles



FLO-2D MODELAREA TOPOGRAPHY



SEP 2012

LegendXXW Modeled Levee Failure

") Modeled Structure Failure

Canal

Model Boundary

Carson River Model Reach

S-Canal Model Reach

V-Canal Model Reach

L-Canal Model Reach

´

Elevation in Feetbelow 3,940

3,940 - 3,950

3,950 - 3,960

3,960 - 3,970

3,970 - 3,980

3,980 - 3,990

3,990 - 4,000

4,000 - 4,020

4,020 - 4,040

4,040 - 4,060

4,060 - 4,100

4,100 - 4,140

above 4,140

PLATE 4

BREACH INUNDATION ANALYSIS “V”, “L”, AND “S” CANALS


WATER SURFACE PROFILE

V CANAL

U.S ARMY CORPS OF ENGINEERS SACRAMENTO DISTRICT

Inflow - 275 CFS

1Canal Stationing begins at the junction of the L and S Canals 2High Water Marks (OWS Max WS) shown were provided by Churchill County 3Vertical Datum is NAVD 88

FIGURE 4




L CANAL


PLATE 5

Inflow - 158 CFS

1Canal Stationing for the L Canal is based off a starting point LC3 near Wildes Rd and Testolin Rd 2High Water Marks (OWS Max WS) shown were provided by Churchill County 3Vertical Datum is NAVD 88

FIGURE 5




S CANAL


PLATE 6

Inflow 40 CFS, Total Flow 157 CFS

1Canal Stationing for the S Canal begins 500 feet upstream of the Reservoir Rd Bridge. 2High Water Marks (OWS Max WS) shown were provided by Churchill County 3The Carson River delivers an additional 40 CFS at Station 14500. 4Vertical Datum is NAVD 88.

Inflow 117 CFS

XXW

CCaa rr ssoo nn RRii vv ee rr


FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

V-Canal #1

£¤95

£¤50

0 1 2Miles



SIMULATED LEVEE BREACH:V-CANAL LOCATION 1,

DEPTH OF INUNDATION



SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal


Inundation Depthbelow 1 foot

1 to 2 feet

2 to 4 feet

above 4 feet

*Mapping only describes inundation from the indicated levee breach, inundationfrom the Carson River or other sources are not included.

´

XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

V-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal


TimeInundation below 1 foot

less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours

greater than 48 hours


´


TIME TO ONE FOOT INUNDATION

XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

V-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal


Feet per Secondless than 0.1

0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1


´


VELOCITY OF FLOODWATER

XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

L-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal

´


1 to 2 feet

2 to 4 feet

above 4 feet

´


SIMULATED LEVEE BREACH:L-CANAL LOCATION 1,

DEPTH OF INUNDATION


XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

L-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal

´


less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´





XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

L-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal

´


0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´





XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

L-Canal #2

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



1 to 2 feet

2 to 4 feet

above 4 feet

´


DEPTH OF INUNDATION


XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

L-Canal #2

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´




XXW



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

L-Canal #2

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´




XXW CCaa rr ssoo nn RRii vv ee rr


FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

S-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



S-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



1 to 2 feet

2 to 4 feet

above 4 feet

´

SIMULATED LEVEE BREACH:S-CANAL LOCATION 1,DEPTH OF INUNDATION




FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

S-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



S-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´


SIMULATED LEVEE BREACH:S-CANAL LOCATION 1,




FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

S-Canal #1

£¤95

£¤50

0 1 2Miles





SEP 2012



S-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´




XXW CCaa rr ssoo nn RR

ii vv ee rr


FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

S-Canal #2

£¤95

£¤50

0 1 2Miles





SEP 2012



S-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



1 to 2 feet

2 to 4 feet

above 4 feet

´

SIMULATED LEVEE BREACH:S-CANAL LOCATION 2,DEPTH OF INUNDATION



ii vv ee rr


FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

S-Canal #2

£¤95

£¤50

0 1 2Miles





SEP 2012



S-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´





ii vv ee rr


FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

flow

S-Canal #2

£¤95

£¤50

0 1 2Miles





SEP 2012



S-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´




")

CCaa rr ss oonn RRii vv ee rr


FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Ha r

rigan

Rd

Fallon

RattlesnakeHill

f low

flo w

VC3

£¤95

£¤50

0 1 2Miles





SEP 2012

Legend") Modeled Structure Failure


V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



1 to 2 feet

2 to 4 feet

above 4 feet

´

SIMULATED INLINE CHECKSTRUCTURE FAILURE:V-CANAL LOCATION 3,

DEPTH OF INUNDATION*Mapping only describes inundation from the indicated levee breach, inundationfrom the Carson River or other sources are not included.

")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Ha r

rigan

Rd

Fallon

RattlesnakeHill

f low

flo w

VC3

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´




")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Ha r

rigan

Rd

Fallon

RattlesnakeHill

f low

flo w

VC3

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´




")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

VC6

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



1 to 2 feet

2 to 4 feet

above 4 feet

´



")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

VC6

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´




")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

VC6

£¤95

£¤50

0 1 2Miles





SEP 2012



V-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´




")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

LC1

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



1 to 2 feet

2 to 4 feet

above 4 feet

´

SIMULATED INLINE CHECKSTRUCTURE FAILURE:L-CANAL LOCATION 1,


")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

LC1

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



less than 2 hours

2 to 6 hours

6 to 12 hours

12 to 24 hours

24 to 48 hours


´




")



FallonMunicipal


Drumm Ln

Union Ln

N A

llen

Rd

Har

r igan

Rd

Fallon

RattlesnakeHill

f low

LC1

£¤95

£¤50

0 1 2Miles





SEP 2012



L-Canal Model Reach

Limit of Mapping*

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal



0.1 to 0.25

0.25 to 0.5

0.5 to 1

greater than 1

´




PLATE 31



TYPICAL V CANAL CROSS SECTION


PLATE 32



TYPICAL L CANAL CROSS SECTION


PLATE 33

BREACH INUNDATION ANALYSIS “V”, L”, AND “S” CANALS


TYPICAL S CANAL CROSS SECTION


SodaLake

ShecklerReservoir Fallon Naval

Air Station

FallonMunicipal

Airport

Drumm Ln

Union LnN A

llen

Rd

Ha r

rigan

Rd

Pas

ture

Rd

CarsonLake

LahontanReservoir

IÄ

!"c$

!

Carson RiverDiversion Dam

DE AD C AME L M O U N TA I NS

HOT S PR I N

GS MO U N TA I N S

f l o

wC a r son River

LL YYOO

NN

CCOO

UUNN

TT YYCC

HHUU

RRCC

HHII LL

LL

CCOO

UUNN

TT YY

FALLON

0 5Miles



FERNLEY LOCATION MAP



NOV 2012

!"c$

I½

LegendCarson River

T-Line Canal

S-Line Canal

V-Line Canal

L-Line Canal

Interstate

Highway

Primary Road

Railroad

County Boundary

Study LocationStudy Location´

Elevation in Feet4,400 to 4,600

4,600 to 4,800

4,800 to 5,000

5,000 to 5,400

5,400 to 5,800

below 3,900

3,900 to 4,000

4,000 to 4,100

4,100 to 4,200

4,200 to 4,300

4,300 to 4,400

FERNLEY

NOV 2012 PLATE 35

BREACH INUNDATION ANALYSIS “V”, “L”, AND “S” ANALYSIS


FERNLEY BREACH PICTURES


Aerial View of Levee Breach in the City of Fernley, NV

Aerial View of Levee Breach in the City of Fernley, NV

NOV 2012 PLATE 36



FERNLEY BREACH PICTURES


Overland Flooding of the City of Fernley, NV

Aerial View of Flooding of the City of Fernley, NV

FIGURE 30




ROUGHNESS SENSITIVITY ANALYSIS V CANAL


PLATE 37

FIGURE 31




ROUGHNESS SENSITIVITY ANALYSIS L CANAL


PLATE 38

FIGURE 5




ROUGHNESS COEFFICIENT ANALYSIS S CANAL


PLATE 39

APPENDIX B

QUALITY CONTROL CERTIFICATE

“v”, “l”, and “s” canals churchill county, nevada

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