urban hydrology
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Urban Hydrology
Construction ImpactsConstruction 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 FenceSilt Fence
HydromulchHydromulch
Control FailureControl Failure
Degradation of Hill Country StreamsDegradation 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.)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.)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.)Degradation of Hill Country Streams (cont.)Road cut along Hamilton Creek
Hamilton Pool--first rain after road cut construction began
Bee CreekBee 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 Austin Rainfall/Runoff
Bear Creek
ShoalCreek
Fort Branch
Boggy Creek
Channel DegradationChannel Degradation
E. Bouldin Creek
Walnut Creek
Tannehill Branch
Shoal Creek
Little Walnut Creek
More of the SameMore of the Same
Shoal CreekShoal Creek
0 10 20 30 40 500
5
10
15
20
25
30
35
Connected imperviousness (%)
Num
ber
of s
peci
es
Y = 10 log10(x)*(-0.585)+1.775 - 1
Types of PollutionTypes 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 RunoffConstituents 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 PollutantsSources 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 PollutantsBuildup of Pollutants
First Flush of PollutantsFirst Flush of Pollutants
Stenstrom & Kayhanian, 2005
Zinc vs. Impervious CoverZinc vs. Impervious Cover
Copper vs. Impervious CoverCopper vs. Impervious Cover
TSS vs. Impervious CoverTSS vs. Impervious Cover
Runoff ConcentrationsRunoff Concentrations
Constituent Avg. C Standard Exceedance
Gross Solids ??? 0 100%
Lead 49 g/L 0.66 97%
Copper 39 g/L 3.2 97%
Zinc 207 g/L 41 52%
Fecal C. 1415 400 42%
Runoff ConcentrationsRunoff 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
Sealants reapplied Sealants reapplied every few years. every few years. About 600,000 About 600,000 gallons of sealant gallons of sealant are applied are applied annually in Austin. annually in Austin.
coal-tar-coal-tar-emulsion-emulsion-sealedsealed
asphalt-asphalt-emulsion-emulsion-sealedsealed
unsealed unsealed asphalt or asphalt or concreteconcrete
Other Sources of PollutantsOther Sources of Pollutants
Sewer Lines in Creeks – Tannehill Branch
Sewer Lines in Creeks – Tannehill Branch
Algae bloomsAlgae bloomsMarch 2, 2002March 2, 2002
Barton Creek Wastewater Leak
Barton Creek Wastewater Leak
Regulatory StrategiesRegulatory 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 RequirementsLocal 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 360Filter System – Lamar & Loop 360
Uniform Distributed Small-scale Controls
Maintaining Natural Hydrology Functions Maintaining Natural Hydrology Functions