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 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 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

Bear Creek Shoal Creek Fort Branch Boggy Creek Channel Degradation

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

Shoal Creek

Types of Pollution Point Sources –Conventionally industrial or wastewater treatment –Any discharge from a pipe or ditch Non-Point Source –Agriculture 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 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 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 ConstituentAvg. CStandardExceedance Gross Solids???0100% Lead 49  g/L % Copper 39  g/L 3.297% Zinc 207  g/L 4152% Fecal C %

Runoff Concentrations ConstituentAvg. C Sediment100 mg/L Nitrate0.93 mg/L TKN2.1 mg/L Total P0.11 mg/L Diss. P1415

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 Other Sources of Pollutants

Sewer Lines in Creeks – Tannehill Branch

Algae blooms March 2, 2002 Barton Creek Wastewater Leak

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