Urban Hydrology Construction Impacts Disturbed areas allow erosion

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 • Plan specifies measures to reduce discharge of sediment

Silt Fence

Hydromulch

Control Failure

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

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

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

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

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

Austin Rainfall/Runoff

Channel Degradation Bear Creek Fort Branch Shoal Creek Boggy Creek

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

Shoal Creek

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

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

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

Buildup of Pollutants

First Flush of Pollutants Stenstrom & Kayhanian, 2005

Zinc vs. Impervious Cover

Copper vs. Impervious Cover

TSS vs. Impervious Cover

Runoff Concentrations Constituent Avg. C Standard Exceedance ? ? ? 0 100% Lead 49 mg/L 0. 66 97% Copper 39 mg/L 3. 2 97% Zinc 207 mg/L 41 52% 1415 400 42% Gross Solids Fecal C.

Runoff Concentrations Constituent Avg. C Sediment 100 mg/L Nitrate 0. 93 mg/L TKN 2. 1 mg/L Total P 0. 11 mg/L Diss. P 1415

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

Sewer Lines in Creeks – Tannehill Branch

Barton Creek Wastewater Leak Algae blooms March 2, 2002

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

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

Filter System – Lamar & Loop 360

Uniform Distributed Small-scale Controls Maintaining Natural Hydrology Functions