Design Elements by pptfiles

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									The Mission Reach Ecosystem Restoration Project:
 Floodplain Management Within a Multi-Objective 
               Project Paradigm




                      Steven Schauer
                 San Antonio River Authority

                  Tim Whitefield, P.E., CFM
                Jacobs Engineering Group Inc.

                        May 24, 2012
Channelized River
 San Pedro
Creek Tunnel

San Antonio
River Tunnel
        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
     MISSION REACH
ECOSYSTEM RESTORATION &
   RECREATION PROJECT
     Restoring Habitat Features
• 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
• OBJECTIVE:
  – Restore aquatic ecosystem function to highly
    degraded river
• CONSTRAINT:
  – Must maintain “zero rise” in the 100 year
    water surface elevation
    Goal For Design Elements
   Add additional functions back into the
    river - but maintain 100-year flood
              carrying capacity

• Pilot Channel – for sediment transport

• Vegetation – maintain flood capacity

• Structures and river features
       Design of Pilot Channel
                 Guidelines:
• Develop understanding of existing sediment yield &
  capacity
• Determine desired regime - yield & capacity
• Size pilot channel for each phase (dimensions &
  slope)
        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
Design of Pilot Channel


               100-Year




                 2-Year


          Effective Flow
                                     Effective 
                                                  2-Year   100-Year
                                       Flow

                  U/S of San Pedro     1180       8292      21284


                  D/S of San Pedro     2320       22426     70396
Design of Pilot Channel
Design of Pilot Channel
    Design of Pilot Channel
• Use riffle structures to establish
  "effective slope", also provide grade
  control



          Effective Slope = 0.0018




                                     Channel Slope = 0.0022
Vegetation
                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
                   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"
                         Vegetation
 WHAT CRITERIA TO USE WHILE APPLYING VARIOUS DENSITIES?


                              BALANCE!

         Hydraulics              vs                    Restoration


Generally, denser areas should            Generally, denser areas near the
  be further from the water              water provide higher quality habitat



  Type A provides the most                 Type A density represents the
  hydraulic resistance, and               most natural condition overtime,
  should be used sparingly                and should be relatively uniform
                                                across the channel
Vegetation
        Vegetation


Type 
 D                   Type 
                      E

Type 
 C

                     Type 
                      A
        Vegetation
                     Type 
                      D


Type                 Type 
 C                    E


Type 
 A
                Structures
•   22 Riffles
•   8 Weirs
•   4 Pedestrian Bridges
•   Toe protection for erosion control
•   Concrete and gravel trails
            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
   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
What Does it Look Like?
                  Questions?


     Steven Schauer           Tim Whitefield, P.E., CFM
San Antonio River Authority            Jacobs
   Manager of External           Hydraulic Engineer
    Communication
                                    817.735.6286
      210-302-3644
                              tim.whitefield@jacobs.com
  sschauer@sara-tx.org

								
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