Leon Creek Watershed Master Plan
Leon Springs Business Association
September 15, 2011
Agenda
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Historic Floods
BRWM Partnership
BRWM Website
Leon Creek Watershed Master Plan
Leon Creek USACE Feasibility Study
Flood of 1921
SAR - Pecan St. Bridge
1998 Flood
vement Projects
Leon Creek - IH10 near Camp Bullis & La Cantera Rd.
2002 Flood
Olmos Creek - Hwy 281/Basse Rd &
Olmos Basin Golf Course
Need for Partnership
• Flooding knows no boundaries
• Sharing of resources
• Project vetting process
Bexar Regional Watershed
Management
• Interlocal Agreement (ILA) established a
partnership for watershed management
between:
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Bexar County (County)
City of San Antonio (COSA)
San Antonio River Authority (SARA)
20 Suburban Cities
BRWM Objectives
• Flood Control
• Storm Water Management
• Water Quality
BRWM website
www.bexarfloodfacts.org
• DFIRM website
– DFIRM floodplains
– Aerial imagery
– NFIP information
• Website will be regularly updated
Leon Springs DFIRM
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Leon Creek Watershed Master Plan
This project will deliver a Holistic Watershed Master Plan
for the Leon Creek watershed
• Flood control projects
• Water quality – qualitative analysis
• Alternative development techniques
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Phase 1 - Regional Detention Projects
Phase 2 - Natural Water Way Conveyance Projects
Phase 3 - Combinations of Phase 1 and Phase 2 projects
Leon Creek Watershed Master Plan
• Leon Creek
Watershed
– Western Bexar
County
– Area: 237 sqmi
– Approximately
1,500 buildings in
the 100-year
floodplain
Damage Density Map
Watershed Annual Flood Damages
• Leon Creek:
$3,064,000
• San Antonio River: $7,703,000
• Salado Creek:
$4,721,500
Note: Damage calculation includes 10-yr, 50yr, 100-yr, 100-yr FC, and 500-yr storm events
Leon Creek Watershed Master Plan
• Phase 1 (April 2008 – December 2008)
– RSWFs
– Stream/roadway crossing analysis
• 14 projects
• Total Cost: $275.6 million
Leon Creek Watershed Master Plan
• Phase 2 (April 2009 –
April 2010)
– NWWC Projects
– Transportation
Corridor & Utility
Crossings
– Stream Scour Analysis
– Alternative
Development
Techniques White
Paper
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21 projects
Total Cost: $147.8 million
Leon Creek Watershed Master Plan
• Phase 3 (May 2010 – January 2011)
– RSWF & NWWC Project combinations
– LIDs, BMPs, NCD, Riparian/conservation
buffers
– Qualitative Water Quality assessment
Leon Creek Watershed Master Plan
• Phase 3
– Non-structural options
evaluation:
• Quantified flood
mitigation of BMPs
• Recommendation:
future development
with BMPs to reduce
hydrologic impact
and drainage
infrastructure
expense
http://imnh.isu.edu
Leon Creek Watershed Master Plan
• Phase 3 BMP & LID Modeling Results
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Rain barrels, rain gardens
Green roofs, pervious pvmt.
Conservation development1
Cisterns, green roofs
Conservation development2
Bioretention and pavement
1. Non-infiltration BMPs
over karst regions (e.g.
rainwater harvesting, green
roofs)
2. Infiltration BMPs (e.g.
bioretention, rain gardens,
pervious pavement)
Bioretention/Rain Gardens
Office Building Rain Garden in Minnesota
http://www.beautifulleafgardens.com/garden_design
Rain Water Harvesting
WaterHarvest Slimline Tank
http://www.gulfcoastrenewableresources.com/rainwater_harvesting
Permeable Pavements
Modular Block Pavement - 1335 Elati St Denver, CO
Photo Courtesty of Wenk Associates
http://www.casfm.org/stormwater_committee/MBP-02.htm
Conservation Development
Traditional Development
Cluster Development minimizes impervious
cover and promotes open or green space.
http://www.upstateforever.org/programs_comDes.html
Cluster Development
LCWMP – Phase 3 Cost Estimates
Total cost :
$140 million
LCWMP – Phase 3 Cost Estimates
Impacts of Implementing All
Recommended Projects
• Flood Damage Reduction
– $1,165,300
• Total Construction Cost
– $140,000,000
• Flood Reduction Ratio
– 0.26
Next Steps for SARA
• Detailed Water Quality Modeling
– Identification of Low Impact Development projects
– Identification of BMPs
• Stream Preservation, Rehabilitation, and
Restoration projects
• DFIRM map maintenance – FEMA LOMR
Delegation for SARA
• Inclusion of Sustainability Practices using TBL
approach
Contacts – Watershed Management
Russell Persyn, PE, PhD, CFM
Manager
(210) 302-3615
rpersyn@sara-tx.org
Rafael Arias Jr., PE, CFM
Engineer
(210) 302-3650
rarias@sara-tx.org
Yolanda McGinnis
Admin. Assistant
(210) 302-3630
yolandam@sara-tx.org
Questions?
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