Forest and Wetlands Important for Protecting Water Quality and Watershed Integrity Background: The objective of the analysis is to identify forests and wetlands important in protecting water quality and sustaining watershed integrity. This "watershed value" is based on physical and biological functions that store precipitation, retain and assimilate nutrients, moderate runoff, protect soils and maintain important critical landscape functions such as those of riparian buffers. These functions, when present, serve to protect water quality. It is well accepted that forests and wetlands are the best land cover for sustaining the integrity of watershed functions and in providing high quality water; therefore the analysis attempts to identify a nexus between a forest or wetland and the parameters that enable these lands to sustain watershed functions. Additionally, it attempts to place a value on wetlands or forests that if lost, would have significant potential to degrade watershed integrity/water quality. Data Layers: Local parameters (scored for each 36.73 meter pixel): Proximity to water Soil Erodibility Slope Wetland function Net primary productivity Forest Fragmentation patch size Hydrogeomorphic regions Floodplains Regional Parameters (Summarized by HUC-11 and scored for each 36.73 meter in the watershed): Stream density Percent of watershed forested Percent of imperviousness Water quality Drinking water supply Methodology: Data was collected for each parameter and an Arc-Info grid raster layer was created and rescaled to 36.73-meter resolution and clipped to represent the Chesapeake Bay watershed. Then each parameter was classified into ranges based on its influence on watershed integrity/water quality and assigned a score (0-4). The parameters were also assigned a weight to emphasize those parameters with greater influence on water quality/watershed integrity. For each individual parameter, the weight was multiplied by the score and a number was assigned to each grid cell. Finally, the corresponding numbers for each grid cell were summed in order to score forests and wetlands for their importance or value in protecting watershed integrity/water quality. ------- Parameters used in to identify the important lands for protecting water quality, along with the rank assigned to the value range and the weight assigned to the parameter. Resource Lands Assessment Topic: Identification and prioritization of areas important to water quality areas for the Resource Lands Assessment (Forest and W etlands) Conservation Priority Index Ranking of value ranges Param eter Data Source Scale 4 3 2 1 W eight li in I'll x Mr.11 I'.i r;i in i-1 l i s (lnr;i 1) L S G S MI D 1 :1 0 0 k 1 SO - 270 m 2 7 0 m 5 Erodible Soils STATSGO (kfact) 1 :250K > .30 (High) .2 - .3 (Moderate) < .2 (None to Slight) 2 Net Prim ary Productivity USFS 1 km 4 3 2 1 3 Slope DEM >15% 15 - 10% 5-10% < 5% 3 1 IMIllinli.il |' .| l.i III i-l c |s (l"l'.lll W etland Function * NWI - cumulative score of w ater- related functions 1 :1 00K score >.3.5 score = 3.0 score <3.0 5 Forest Fragm entation - Patch Size (HA) CBP 1 :1 00K > 1000 400 - 1000 100 - 400 <100 2 FEMA 100 year flood plain FEMA Yes 2 - - - ' ~ : l< i-iiinn.i I \\ .i ii-i-s|ii-d I'.i r.i in i-li-I's Stream Density-m eters/sqkm NHD 1 :100K > 1.042 0.77 - 1.042 0.524 - 0.769 0 - 0.523 4 % Forested MRLC 1997 1 :1 00K 40 - 65% 30 - 40; 65 - 75% 15 - 30; 75 - 85% < 1 5 ; > 8 5 % 3 % Impervious Surface MRLC 1997 1 :1 00K 5 to 1 5 % < 5% 15 to 25% > 25% 2 W ater Q uality Sparrow/DU 1 :100K Good Fair Very Good Poor 5 Municipal Surface W ater Supplies USGS - pop. Served/ # of intakes 1 :1 00K High/H igh, High/Med, Med/High, Low/High, H igh/L o w Med/Med Med/Low, Low/Med Low/Low 4 ------- |