Storm Drain Mapping and Impervious Surfaces in SF Bay Urban Areas

1. San Francisco Estuary Institute Storm Drain Mapping and Impervious Surfaces in SF Bay Urban Areas Impervious Surface Data Collection Workshop Regional Board October 11th 2005 Lester McKee San Francisco Estuary Institute

2. San Francisco Estuary Institute Regional Storm Drain Mapping Objective • Map >24 inch diameter stormwater conveyance systems of the Bay Area Team • Christopher Richard - Oakland Museum of California • Janet Sowers - William Lettis and Associates Inc. • Robin Grossinger - San Francisco Estuary Institute • Trish Mulvey – Clean South Bay / SFEI Board Period of Performance • 1993 - present

3. San Francisco Estuary Institute Progress

4. San Francisco Estuary Institute Linkages Between Storm Drain Mapping and Impervious data • Planning at the Bay scale • Modeling runoff of water, sediment and contaminant loads for improved problem definition during TMDL adaptive implementation • Planning at the watershed scale • Modeling for drainage design • Modeling for understanding channel maintenance needs • Modeling to understand the processes of contaminant sources, release, and transport

5. San Francisco Estuary Institute Other Uses(in the context of permits and TMDLs) • Planning at the site scale • Performance standards in new development and redevelopment (e.g. zero new EIA) • Education tool for increasing awareness of compacted soils* as TIA • Planning at the community, regional or watershed scale • No net increase towards agreed upon thresholds • Alternative futures analysis (modeling to determine how best to get to agreed upon thresholds) • Decision support for reaching hydro-modification or TMDL goals (e.g. area of EIA disconnected annually)

6. San Francisco Estuary Institute Definition of an Impervious Surface (Arnold and Gibbons, 1996) “Any material that prevents the infiltration of water into soil” • Roads, rooftops, parking lots • Sidewalks, patios, bedrock outcrops, and compacted soils*

7. San Francisco Estuary Institute Total Impervious Area (TIA)versusEffective Impervious Area (EIA) • TIA includes all impervious surfaces • A portion of rain will infiltrate when it runs onto lawns, swales, or driveways • EIA includes only impervious surfaces that drain to stormwater conveyances or receiving waters • 100% of rain runs off EIA

8. San Francisco Estuary Institute Methods • Direct • Digitization of aerial photography • Classification of remotely sensed (satellite) images • Collation of development / redevelopment plans • Indirect (mathematical relationships) • Conversion of land use data • Conversion of population density data

9. San Francisco Estuary Institute TIA/EIA as an Indicator of Urban Impact to Surface Waters • About 30-40 papers written prior to 2002 • See recent review articles: • Paul and Meyer, 2001. Streams in the urban landscape. • Gergel et al., 2002. Landscape indicators of human impacts to riverine systems. • Brabec et al., 2002. Impervious surfaces and water quality: A review of current literature and its implications for watershed planning.

10. San Francisco Estuary Institute Linkage to Flow Hydrology? YES • Peak flow • Bankfull flow • Total volume % Impervious surfaces

11. Flow Time from beginning of rain Flow Time from beginning of rain San Francisco Estuary Institute Location of TIA / EIA • Lower watershed • Upper watershed

12. San Francisco Estuary Institute Linkage to Physical Impacts? YES • Channel widening/ enlarging • Sediment loads • Stream temperature % Impervious surfaces

13. San Francisco Estuary Institute Linkage to Contaminants? YES • Transmission of contaminants from sources • Contaminant loads • Eutrophication % Impervious surfaces

14. San Francisco Estuary Institute Linkage to Biological Impacts? YES • Habitat quality and diversity • Insect/ invertebrate diversity • Fish numbers and diversity % Impervious surfaces

15. San Francisco Estuary Institute Noticeable Impacts and Thresholds • Noticeable Impacts (see reviews Brabec et al., 2002; Gergel et al., 2002) • Physical • Flow 5-50% • Channel form 2-30% • Chemical 8-50% • Biological • Fish 4-15% • Macro-inverts 8-15% • Thresholds (Schueler, 1995; Arnold and Gibbons, 1996) • Protected <10% • Impacted 10-30% • Degraded >30%

16. San Francisco Estuary Institute Summary (TIA / EIA) • Very good (if not best) indicator of urban impacts to surface waters • Need agreed upon regional definitions and methods • Data can be used for planning at virtually every scale • Data can be combined with storm drain mapping to develop watershed and regional hydrological models

17. San Francisco Estuary Institute Literature • Schueler, 1994. The importance of imperviousness. Watershed Protection Techniques 1, 100-111. • Schueler, 1995. The peculiarities of imperviousness. Watershed Protection Techniques 2, 233-238. • Arnold and Gibbons, 1996. Impervious surface coverage: The emergence of a key environmental indicator. Journal of the American Planning Association 62, 243-258. • Paul and Meyer, 2001. Streams in the urban landscape. Annual review of Ecology and Systematics 32, 333-365. • Brabec et al., 2002. Impervious surfaces and water quality: A review of current literature and its implications for watershed planning. Journal of Planning Literature 16, 499-514. • Gergel et al., 2002. Landscape indicators of human impacts to riverine systems. Aquatic Sciences 64, 118-128.