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
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Urban Hydrology
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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
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Silt FenceSilt Fence
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HydromulchHydromulch
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Control FailureControl Failure
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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
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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
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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
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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
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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
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Austin Rainfall/Runoff Austin Rainfall/Runoff
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Bear Creek
ShoalCreek
Fort Branch
Boggy Creek
Channel DegradationChannel Degradation
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E. Bouldin Creek
Walnut Creek
Tannehill Branch
Shoal Creek
Little Walnut Creek
More of the SameMore of the Same
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Shoal CreekShoal Creek
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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
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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
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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
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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
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Buildup of PollutantsBuildup of Pollutants
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First Flush of PollutantsFirst Flush of Pollutants
Stenstrom & Kayhanian, 2005
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Zinc vs. Impervious CoverZinc vs. Impervious Cover
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Copper vs. Impervious CoverCopper vs. Impervious Cover
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TSS vs. Impervious CoverTSS vs. Impervious Cover
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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%
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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
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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
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Sewer Lines in Creeks – Tannehill Branch
Sewer Lines in Creeks – Tannehill Branch
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Algae bloomsAlgae bloomsMarch 2, 2002March 2, 2002
Barton Creek Wastewater Leak
Barton Creek Wastewater Leak
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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
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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
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Filter System – Lamar & Loop 360Filter System – Lamar & Loop 360
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Uniform Distributed Small-scale Controls
Maintaining Natural Hydrology Functions Maintaining Natural Hydrology Functions