Alluvial Bar Morphology and Dynamics in the Middle Rio

Grande: Application to Habitat Restoration for the Rio Grande

Silvery Minnow

Alluvial Bar Morphology and Alluvial Bar Morphology and Dynamics in the Middle Rio Dynamics in the Middle Rio

Grande: Application to Habitat Grande: Application to Habitat Restoration for the Rio Grande Restoration for the Rio Grande

Silvery MinnowSilvery Minnow

Mike Harvey

MMussetter EEngineering, IInc.

WORK CONDUCTED FOR:WORK CONDUCTED FOR:

New Mexico Interstate Stream Commission

Middle Rio Grande ESA Collaborative Program

WHAT IS A BAR ?WHAT IS A BAR ?

“Discrete alluvial feature formed by deposition and modified by erosion”

– Can be mid-channel or bank-attached– Can be subaerial or subaqueous– Can be stationary or mobile– Can be vegetated or unvegetated

?

PROJECT OBJECTIVESPROJECT OBJECTIVES

Evaluate bar changes over time in response to changes in flow, sediment supply and channel morphologyDevelop a bar classificationRelate fluvial processes to bar typesApply results to river/habitat restoration

MEI

9 STUDY SITES

MEI

1935 1955 1972

1992

1996 2001

Modified Braiding IndexModified Braiding Index((GermanoskiGermanoski, 1989), 1989)

Channel

bars

Channel

BraidBar

Ln

LL

MBI += ∑ )(2

EXPECTED MBI RESPONSESEXPECTED MBI RESPONSES((GermanoskiGermanoski and and SchummSchumm, 1993; , 1993; GermanoskiGermanoski and Harvey, 1993)and Harvey, 1993)

If D50 increases, and there is sediment supply: > MBI

If D50 increases, and there is no sediment supply: < MBI

If the bed aggrades: > MBI

If the bed degrades: < MBI

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

1935 1945 1955 1965 1975 1985 1995

Year

Bar

Inde

x

0

200

400

600

800

1000

1200

1400

1600

Ave

rage

Cha

nnel

Wid

th (f

t)

Modified Braid Bar Index

Alternate Bar Index

Active Channel Width

0.00

0.50

1.00

1.50

2.00

2.50

3.00

1935 1945 1955 1965 1975 1985 1995

Year

Bar

Inde

x

0

200

400

600

800

1000

1200

1400

Ave

rage

Cha

nnel

Wid

th (f

t)

Modified Braid Bar Index

Alternate Bar Index

Active Channel Width

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

1935 1945 1955 1965 1975 1985 1995

Year

Bar

Inde

x

0

200

400

600

800

1000

1200

1400

1600

Ave

rage

Cha

nnel

Wid

th (f

t)

Modified Braid Bar Index

Alternate Bar Index

Active Channel Width

Pena Blanca Central Avenue

Bernardo

0.00

0.50

1.00

1.50

2.00

2.50

3.00

1935 1945 1955 1965 1975 1985 1995

Year

Bar

Inde

x

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Ave

rage

Cha

nnel

Wid

th (f

t)

Modified Braid Bar Index

Alternate Bar Index

Active Channel Width

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1972 1982 1992 2002

Year

Bar

Inde

x

0

50

100

150

200

250

Ave

rage

Cha

nnel

Wid

th (f

t)

Modified Braid Bar Index

Alternate Bar Index

Active Channel Width

Bosque del Apache San Marcial

0.00

0.50

1.00

1.50

2.00

2.50

1947 1957 1967 1977 1987 1997

Year

Bar

Inde

x

0

100

200

300

400

500

600

700

800

900

1000

Ave

rage

Cha

nnel

Wid

th (f

t)

Modified Braid Bar Index

Alternate Bar Index

Active Channel Width

Escondida

YesSubaerialLevel-1,2Bank-attachedBank-attachedYesSubaerialLevel-1,2Mid-channelMid-channelNoSubaerialLevel-1Bank-attachedAlternateNoSubaerialLevel-1,2Mid-channelBraidNoSubaqueousBedMid-channelLinguoid

PerennialVegetation

Subaqueousor SubaerialElevationLocationBar Type

Hierarchical Bar Classification for the Middle Rio Grande

Hierarchical Bar Classification Hierarchical Bar Classification for the Middle Rio Grandefor the Middle Rio Grande

MEI

Linguoid bar

L-1 braid bars

L-1 braid bar

mud drape

L-2 braid bar

L-1 bank-attached bar

L-1 braid bar

L-1 mid-channel barL-2 braid bar

Linguoid bar

L-2 braid bar

L-2 mid-channel bar

L-1 mid-channel bar

L-2 mid-channel bar

L-2 bank-attached bar

L-1 bank-attached bar

HYDRAULIC ANALYSISHYDRAULIC ANALYSIS

One-dimensional HEC-RAS models

– Fixed-bed analysis– Calibrated to gauged flow at time of

survey and 2005 peak flow (Tetra Tech. (2005)

Central SiteCentral SiteBar Inundation Analysis

1.9-yr

2.9-yr

1.7-yr1.6-yr

1.1-yr

<1.01-yr

<1.01-yr

1.5-yr1.5-yr1.4-yr1.4-yr

1.03-yr

<1.01-yr

<1.01-yr

2.9-yr

5-yr

2.7-yr2.7-yr

1.4-yr

1.1-yr1.05-yr

<1.01-yr

4%

1%

4%5%

12%

29%

47%

95%

6%6%7%8%

21%

51%

91%98%

1%

0%

1%1%

7%

16%17%

92%

0

1000

2000

3000

4000

5000

6000

7000

8000

Linguoid Bar Level-1 Braid Bar

Alternate Bar

Level-2 Braid Bar

Level-1 Mid-Channel Bar

Level-1 Bank-Attached Bar

Level-2 Mid-Channel Bar

Level-2 Bank-Attached Bar

Bar Feature

Dis

char

ge (c

fs)

Mean Inundation Discharge

Minimum Inundation Discharge

Maximum Inundation DischargeMean Channel Capacity

Mean-daily exceedance percent and peak flood return interval of inudation discharge show n next to plotted value.

BAR INUNDATION BAR INUNDATION FREQUENCY & DURATIONFREQUENCY & DURATION

Table ES-1. Summary of frequency and duration of inundation of the

classified bar types at sites without excessive aggradation or degradation.*

Bar Type Inundation Recurrence

Interval

Days per Year of

Inundation

Percent of Year

Inundated Level 1 braid bars < 1 year 290 80% Alternate bars < 1 year 290 80% Level 2 braid bars < 1 year 146 <40% Level 1 mid-channel bars 1.5 years 90 25% Level 1 bank-attached bars 1.5 years 90 25% Level 2 mid-channel bars 2 years 36 <10% Level 2 bank-attached bars 2 years 36 <10%

*excluding the Pena Blanca, Bernalillo, Escondida and San Marcial sites.

BARS AND SHEAR STRESSBARS AND SHEAR STRESS

Table ES-2: Comparison of maximum in-channel shear stresses to the prevalence of bars in the sand-bed sites.

Site Names

Maximum In-Channel Shear

Stresses (lb/ft2)

Prevalence of Active Bars

Central Avenue <0.1 moderate to high number of active bars Bosque del Apache, San Marcial 0.1 high number of active bars Bernardo, La Joya, Lemitar 0.12 - 0.15 active bars are present Belen 0.2 moderate number of active bars Escondida 0.3 virtually no active bars

BARS AND VEGETATIONBARS AND VEGETATION

Shear stress limit for vegetation establishment ~ < 1 psfShear stress limit for vegetation removal ~ > 6 psf

Central Site Central Site –– Cross Section 2Cross Section 2

1000 1200 1400 1600Station (ft)

4945

4946

4947

4948

4949

4950

4951

4952

4953

Elev

atio

n (ft

)

Ground ElevationLingouid BarL1 Braid BarL2 Braid BarL1 Mid-ch BarComputed Water-Surface Elevation

0 100 200 300Number of Days (Mean-Daily Duration)

1.5-yr

2-yr

5-yr

10-yr

25-yr

50-yr100-yr

1 2 5 10 20 30 40 50 60 70Peak Exceedance Percent

Mean-Daily DurationPeak FrequencyShear Stress

0 0.1 0.2 0.3Shear Stress (lb/ft2)

737 cfs

329 cfs

1,055 cfs

2,110 cfs

3,490 cfs

4,450 cfs

5,410 cfs

7,600 cfs

BARS AND DEPOSITIONBARS AND DEPOSITION

Based on surveys of L1 and L2 bars in Albuquerque Reach, pre- and post-2005 high flows

Comparison based on 0.5 ft contour-interval topographic mapping

L1

POST-HIGH FLOWSEDIMENT DEPOSITION

2005

UpstreamBar

High Flow

UpstreamBar

Low Flow

DownstreamBar

High Flow

L1 L2 L2L1

L1

BARS AND DEGRADATIONBARS AND DEGRADATION

Degradation causes hydrologic abandonment of bars

If restoration is being considered is the bed currently stable?

If degradation continues, restoration will be compromised

Abandoned L-2 mid-channel bar

Bernalillo SiteBernalillo SiteBar Inundation Analysis

13.5-yr

4.2-yr3.6-yr

1.6-yr

1.2-yr

<1.01-yr

1.8-yr

1.3-yr1.2-yr

1.03-yr<1.01-yr

100-yr

10.1-yr8.6-yr

4.6-yr4.4-yr

0%

0%0%

6%

11%

32%

4%

8%9%

20%31%

33%

0%

0%0%

0%0%

32%

0

2000

4000

6000

8000

10000

12000

14000

Linguoid Bar Level-1 Braid Bar

Alternate Bar

Level-2 Braid Bar

Level-1 Mid-Channel Bar

Level-1 Bank-Attached Bar

Level-2 Mid-Channel Bar

Level-2 Bank-Attached Bar

Bar Feature

Dis

char

ge (c

fs)

Mean Inundation DischargeMinimum Inundation DischargeMaximum Inundation DischargeMean Channel Capacity

Mean-daily exceedance percent and peak f lood return interval of inudation discharge show n next to plotted value.

No

Ling

uoid

Bar

s Id

entif

ied

in S

tudy

Rea

ch

No

Leve

l-1 B

ank-

Atta

ched

Bar

s Id

entif

ied

in S

tudy

Rea

ch

Bernalillo Site Bernalillo Site –– Cross Section 10Cross Section 10

1000 1200 1400 1600 1800 2000Station (ft)

5046

5048

5050

5052

5054

5056

5058

5060

Elev

atio

n (ft

)

Ground ElevationL1 Braid BarAlternate BarL2 Braid BarL1 Bank-att BarL2 Mid-ch BarL2 Bank-att BarComputed Water-Surface Elevation

0 100 200 300Number of Days (Mean-Daily Duration)

1.5-yr

2-yr

5-yr10-yr

25-yr50-yr

100-yr

1 2 5 10 20 30 40 50 60 70Peak Exceedance Percent

Mean-Daily DurationPeak FrequencyShear Stress

737 cfs882 cfs1,055 cfs

2,110 cfs

3,490 cfs

4,450 cfs5,410 cfs

7,600 cfs8,940 cfs

0 0.1 0.2 0.3Shear Stress (lb/ft2)

Bernalillo SiteBernalillo Site

1.5 2 5 10 25 50 100

0

0.5

1

1.5

2

1000 3000 5000 7000 9000 11000 13000Discharge (cfs)

Dim

ensi

onle

ss G

rain

She

ar

Reach Averaged Hydraulics, D50=37 mm (WC4)

XS8 Hydraulics, D50=37 mm (WC4)

RI (years)

CONCLUSIONSCONCLUSIONS

Bar indices reflect changes in flow, sediment supply and channel morphology

Bar classification is a communication tool, and provides first-cut hydraulic assessments

CONCLUSIONSCONCLUSIONS

Active braid bars require average shear stresses < 0.2 psfInundation of bars leads to vertical growth and reduced frequency and duration of inundationDegradation will adversely affect restoration efforts, so vertical stability must be assessed

APPLICATION TO APPLICATION TO RESTORATIONRESTORATION

Bridge Blvd.

RIO GRANDE SILVERY MINNOWRIO GRANDE SILVERY MINNOWTARGETED LIFE STAGES:-EGGS - LARVAE- JUVENILES

BIOLOGICAL TARGET25 DAYS INUNDATION(~ 7 % EXCEEDENCE)

POST-COCHITI (1974 -2005)Flow Duration Curve:~ 4000 CFS

PHYSICAL NEEDS-LOW VELOCITY-SHALLOW DEPTH

10 30 50 70 9010.10.01 99 99.995Percent of Time Equaled or Exceeded

0.1

1

10

100

1,000

10,000

Dis

char

ge (c

fs)

DryNormalWet

Rio Grande at Albuquerque, NM (Central Ave.)USGS Gage no. 08330000

Flow Duration Curves

25-D

ay E

xcee

danc

e

Class

25-day Exceedance Discharge

(cfs)Dry 1426

Normal 3493Wet 5601

4953.7

4955.1

4956.3

4952

4953

4954

4955

4956

4957

4958

4959

100 1000 10000 100000

Discharge (cfs)

Wat

er-S

urfa

ce E

leva

tion

(ft)

Central Avenue Site (Section 13)

1430

cfs

(Dry

25-

day

Exce

eden

ce)

3500

cfs

(Nor

mal

25-

day

Exc

eede

nce)

5600

cfs

(Wet

25-

day

Exc

eede

nce)

Bridge Blvd.

Rio Grande Phase II

9.4

55.1

832.5

8.534.5

127.4

519

8

51.2

95.2

756.2

5.5 21.5 33.3

293.2

244.5

0

100

200

300

400

500

600

700

800

900

1400 cfs 3500 cfs 5600 cfs >6500 cfs

Discharge (cfs)

Are

a of

Inun

datio

n (a

cres

)

SDCI-40PDNNDC

Note: Areas of inundation represent habitat increases at discharges greater than 1,000 cfs.

Rio Grande Phase II

1.59.0

135.5

1.87.4

27.2

110.9

1.8

11.4

21.1

167.8

2.510.0

15.4

135.8

39.8

0

20

40

60

80

100

120

140

160

180

1400 cfs 3500 cfs 5600 cfs >6500 cfs

Discharge (cfs)

Are

a of

Inun

datio

n (a

cres

) / C

hann

el M

ile

SDCI-40PDNNDC

Note: Areas of inundation represent habitat increases at discharges greater than 1,000 cfs.

Potential Site

Bar Classification Reject

RejectSite

Availability & Constraints

Design Criteria -Egg Retention -Juvenile Habitat

Hydrologic Analysis-25-day duration (6.8% Exceedence)

Design Discharge1,400 cfs 5,600 cfs

3,500 cfs

Hydraulics (HEC-RAS, FLO-2D)Water-Surface Elevation

Design Elevation

L-II mcb, bab

bb, ab L-I mcb, bab

Prior Use Private Property Infrastructure Impacts

Available No Infrastructure Impacts

Dry Wet

Normal

SITE SELECTION SCREENING TOOL

98000 100000 102000 104000 106000 108000 110000 112000 114000Station (ft)

4970

4975

4980

4985

4990

4995

5000El

evat

ion

(ft)

6500 cfs5600 cfs3500 cfs2500 cfs1400 cfs300 cfsPhase II FeaturesChannel Bed

13i

12i

11i3b

10i

9i

8i7i North

6i North6i South6i Chan

14i1b South4i

3i2i

7i SouthFeature Areas(acres)PDN 13i - 3.32PDN 12i - 1.0PDN 11i - 2.76PDN 3b - 1.52PDN 10i - 0.1PDN 9i - 6.25PDN 8i - 0.7PDN 7i - 0.34PDN 6i - 2.63PDN 14i - 1.3PDN 1b - 1.73PDN 4i - 0.3PDN 3i - 2.02PDN 2i - 2.81

TAKE HOME MESSAGESTAKE HOME MESSAGESRestoration requires a clear understanding of river dynamics and biological objectives.Must be able to translate biological objectives into physical parameters to provide a basis of design.Bar classification provides a first-cut tool for relating fluvial process to habitat requirements and initial site selection.