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![Page 1: The Mission Reach Ecosystem Restoration Project: Floodplain Management Within a Multi-Objective Project Paradigm Steven Schauer San Antonio River Authority.](https://reader034.fdocuments.in/reader034/viewer/2022051315/56649d1f5503460f949f2dea/html5/thumbnails/1.jpg)
The Mission Reach Ecosystem Restoration Project:Floodplain Management Within a Multi-Objective
Project Paradigm
Steven SchauerSan Antonio River Authority
Tim Whitefield, P.E., CFMJacobs Engineering Group Inc.
May 24, 2012
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CREEK
ALAZAN
CR
EE
K
RIVER
SAN
AN
TON
IO
ALAMO ST.
NUEVA ST.
HILDEBRAND AVE.
LEXIN
GTO
N AVE.
LEGEND
TRIBUTARY
HEAD WATERS
MISSIONESPADA
35
37
35
410
9090
81
81
281
281
CR
EE
K
SAN
PED
RO
APACHE
W E
S
N
10
10
SAN JUANMISSION
SAN JOSEMISSION
CONCEPCIONMISSION
SAN ANTONIODOWNTOWN
CR
EE
K
MA
RT
INE
Z
ORIGINAL ALIGNMENTSOUTH OF DOWNTOWN
SACIP
Channelized River
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San Pedro Creek Tunnel
San Antonio River Tunnel
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MISSION REACH
• Partnership project between: – U.S. Army Corps of Engineers– San Antonio River Authority– Bexar County– City of San Antonio– San Antonio Water System– San Antonio River Oversight Committee– San Antonio River Foundation
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MISSION REACHECOSYSTEM RESTORATION & RECREATION
PROJECT
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• 23,500+ young trees & shrubs• 320 acres of riparian woodland habitat• 113 acres of aquatic habitat • 30 riffles/weirs • 13+ acres of embayment• 2 river remnants: San Juan & Espada
Restoring Habitat Features
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• OBJECTIVE:– Restore aquatic ecosystem function to highly
degraded river• CONSTRAINT:
– Must maintain “zero rise” in the 100 year water surface elevation
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Goal For Design Elements
• Pilot Channel – for sediment transport
• Vegetation – maintain flood capacity
• Structures and river features
Add additional functions back into the river - but maintain 100-year flood
carrying capacity
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Design of Pilot Channel
• Develop understanding of existing sediment yield &
capacity
• Determine desired regime - yield & capacity
• Size pilot channel for each phase (dimensions &
slope)
Guidelines:
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Design of Pilot Channel
• Pilot channel sized to carry "effective discharge"
• Hypothetical value presumed to transport most of the
sediment over time
• Flow for which frequency and sediment transport are
maximized
• Typically 1-2 year recurrence - can be more frequent
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Design of Pilot Channel
Effective
Flow2-Year 100-Year
U/S of San Pedro 1180 8292 21284
D/S of San Pedro 2320 22426 70396
2-Year
Effective Flow
100-Year
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Design of Pilot Channel
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Design of Pilot Channel
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Design of Pilot Channel
• Use riffle structures to establish "effective slope", also provide grade control
Effective Slope = 0.0018
Channel Slope = 0.0022
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Vegetation
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Vegetation
• Density:– Trees will be planted in 3 densities to model
various riparian conditions:– “A” – 250 trees per acre (~13 ft. o.c.)– “C” – 70 trees per acre (~25 ft. o.c.)– “D” – 27 trees per acre (~40 ft. o.c.)– “E” – herbaceous vegetation only – no trees
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Vegetation
•Manning's “n” values for project– Zone “A” – 0.15 – Zone “C” - 0.085– Zone “D” – 0.055– Zone “E” – 0.035
--Desire is for entire project to be suite "A" --Exceptions are considered "hydraulic concessions"
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Vegetation
Generally, denser areas should be further from the water
Type A density represents the most natural condition overtime, and should be relatively uniform
across the channel
Generally, denser areas near the water provide higher quality habitat
Type A provides the most hydraulic resistance, and should be used sparingly
BALANCE!
RestorationHydraulics vs
WHAT CRITERIA TO USE WHILE APPLYING VARIOUS DENSITIES?
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Vegetation
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Vegetation
Type A
Type C
Type D Type
E
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Vegetation
Type E
Type D
Type C
Type A
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Structures
• 22 Riffles• 8 Weirs• 4 Pedestrian Bridges• Toe protection for erosion control• Concrete and gravel trails
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River Features
•8 Embayments•2 “Run” segments•30 “Pool” segments•8 Scour Pools•2 Restored river remnants•7.5 acre “bottomland hardwood forest”•320 acres of wooded riparian corridor
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What is an Embayment?
• Man-made habitat features that tend to simulate oxbows
• Shallow water adjacent to channel• Increase surface area, shoreline length• Add variation to velocity and depth• Create habitat for plants & fish
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What Does it Look Like?
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Questions?
Steven Schauer
San Antonio River Authority
Manager of External Communication
210-302-3644
Tim Whitefield, P.E., CFM
Jacobs
Hydraulic Engineer
817.735.6286