Leon Creek Watershed Master Plan
Leon Springs Business Association
September 15, 2011
Agenda• Historic Floods• BRWM Partnership• BRWM Website• Leon Creek Watershed Master Plan• Leon Creek USACE Feasibility Study
Flood of 1921
SAR - Pecan St. Bridge
1998 Floodvement Projects
Leon Creek - IH10 near Camp Bullis & La Cantera Rd.
Olmos Creek - Hwy 281/Basse Rd & Olmos Basin Golf Course
2002 Flood
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:• 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
• DFIRM website– DFIRM floodplains– Aerial imagery–NFIP information
• Website will be regularly updated
BRWM websitewww.bexarfloodfacts.org
10
Leon Springs DFIRM
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
• 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, 50-yr, 100-yr, 100-yr FC, and 500-yr storm events
• Phase 1 (April 2008 – December 2008)– RSWFs– Stream/roadway crossing analysis
Leon Creek Watershed Master Plan
• 14 projects
• Total Cost: $275.6 million
• Phase 2 (April 2009 – April 2010) – NWWC Projects– Transportation
Corridor & Utility Crossings
– Stream Scour Analysis
– Alternative Development Techniques White Paper
Leon Creek Watershed Master Plan
• 21 projects• Total Cost: $147.8 million
• 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
Leon Creek Watershed Master Plan
http://imnh.isu.edu
• Phase 3 BMP & LID Modeling Results
Leon Creek Watershed Master Plan
• 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
http://www.beautifulleafgardens.com/garden_design
Office Building Rain Garden in Minnesota
Rain Water Harvesting
http://www.gulfcoastrenewableresources.com/rainwater_harvesting
WaterHarvest Slimline Tank
Permeable Pavements
http://www.casfm.org/stormwater_committee/MBP-02.htm
Modular Block Pavement - 1335 Elati St Denver, COPhoto Courtesty of Wenk Associates
Conservation Development
http://www.upstateforever.org/programs_comDes.html
Cluster Development minimizes impervious cover and promotes open or green space.
Traditional Development 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, CFMManager(210) [email protected]
Rafael Arias Jr., PE, CFMEngineer(210) [email protected]
Yolanda McGinnisAdmin. Assistant(210) [email protected]
Questions?
31
32
