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Urban Hydrology

Urban Hydrology. Construction Impacts. Disturbed areas allow erosion to occur High concentrations of sediment can impact creeks and ponds Construction General Permit Storm Water Pollution Prevention Plan (SWPPP) must be prepared for project

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Urban Hydrology

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  1. Urban Hydrology

  2. Construction Impacts • Disturbed areas allow erosion to occur • High concentrations of sediment can impact creeks and ponds • Construction General Permit • Storm Water Pollution Prevention Plan (SWPPP) must be prepared for project • Plan specifies measures to reduce discharge of sediment

  3. Silt Fence

  4. Hydromulch

  5. Control Failure

  6. Degradation of Hill Country Streams Green Hole on Lick Creek, west Travis County, Summer 2003 Green Hole on July 27, 2004, after rainfall caused overflow from the West Cypress Hills subdivision detention pond for development construction

  7. Degradation of Hill Country Streams (cont.) Dead Mans Hole on Dead Mans Creek, east Hays County, before construction of a small dam in the watershed Dead Mans Hole after construction of the dam

  8. Degradation of Hill Country Streams (cont.) Road cut for land development in Hamilton Creek basin began June, 2007 Hamilton Pool prior to June 2007

  9. Degradation of Hill Country Streams (cont.) Road cut along Hamilton Creek Hamilton Pool--first rain after road cut construction began

  10. Bee Creek Bee Creek near Hwy 71, West Travis County, prior to development in basin Bee Creek, August 2007, immediately after development began in basin

  11. Austin Rainfall/Runoff

  12. Bear Creek Channel Degradation Fort Branch ShoalCreek Boggy Creek

  13. More of the Same Little Walnut Creek E. Bouldin Creek Shoal Creek Walnut Creek Tannehill Branch

  14. Shoal Creek

  15. Types of Pollution • Point Sources • Conventionally industrial or wastewater treatment • Any discharge from a pipe or ditch • Non-Point Source • Agriculture

  16. Constituents in Urban Runoff • Bacteria • Nutrients • Insecticides • Herbicides • Metals – zinc, copper, lead • Hydrocarbons – PAHs • Sediment

  17. Sources of Pollutants • Vehicles – Tires, Brake pads, Fluids, Tracking • Atmospheric Deposition • Fertilizers • Pesticides • Pets • Pavement abrasion • Channel Erosion

  18. Buildup of Pollutants

  19. Stenstrom & Kayhanian, 2005 First Flush of Pollutants

  20. Zinc vs. Impervious Cover

  21. Copper vs. Impervious Cover

  22. TSS vs. Impervious Cover

  23. Runoff Concentrations

  24. Runoff Concentrations

  25. Other Sources of Pollutants Sealants reapplied every few years. About 600,000 gallons of sealant are applied annually in Austin. coal-tar-emulsion-sealed asphalt-emulsion-sealed unsealed asphalt or concrete

  26. Sewer Lines in Creeks – Tannehill Branch

  27. Barton Creek Wastewater Leak Algae blooms March 2, 2002

  28. Regulatory Strategies • Do nothing • Do something (structural) • Meet a performance standard • Meet water quality standards

  29. Local Requirements • Austin – Achieve pollutant reduction comparable to a sand filter system, or “no discharge” of stormwater. • LCRA – Reduce TSS, TP, and O&G by 75% • TCEQ – Reduce the increase in TSS discharged by 80%. • Houston – Do something

  30. Filter System – Lamar & Loop 360

  31. Uniform Distributed Small-scale Controls Maintaining Natural Hydrology Functions

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