McKee 10 11 05

Storm Drain Mapping and Impervious Surfaces in SF Bay Urban Areas: 

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

Regional Storm Drain Mapping: 

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

Slide3: 

Progress

Linkages Between Storm Drain Mapping and Impervious data: 

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

Other Uses(in the context of permits and TMDLs): 

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)

Definition of an Impervious Surface (Arnold and Gibbons, 1996): 

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*

Total Impervious Area (TIA)versusEffective Impervious Area (EIA): 

Total Impervious Area (TIA) versus Effective 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

Methods: 

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

TIA/EIA as an Indicator of Urban Impact to Surface Waters: 

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.

Linkage to Flow Hydrology? YES: 

Linkage to Flow Hydrology? YES % Impervious surfaces Peak flow Bankfull flow Total volume

Location of TIA / EIA: 

Location of TIA / EIA Lower watershed Upper watershed

Linkage to Physical Impacts? YES: 

Linkage to Physical Impacts? YES % Impervious surfaces Channel widening/ enlarging Sediment loads Stream temperature

Linkage to Contaminants? YES: 

Linkage to Contaminants? YES % Impervious surfaces Transmission of contaminants from sources Contaminant loads Eutrophication

Linkage to Biological Impacts? YES: 

Linkage to Biological Impacts? YES % Impervious surfaces Habitat quality and diversity Insect/ invertebrate diversity Fish numbers and diversity

Noticeable Impacts and Thresholds: 

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%

Summary (TIA / EIA): 

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

Literature: 

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.