National Fish Habitat Action Plan (NFHAP) 2010 HCI Scores - by HUC8

This shapefile contains summaries of habitat condition indices (HCI scores) from the National Fish Habitat Action Plan (NFHAP) 2010 National Assessments for 8 digit Hydrological Unit Codes (HUC8s) of the United States. Initial HCI scores were developed in three separate assessments (Conterminous U.S., Hawaii, and Alaska) due to differences in data availability across these regions. In the initial NFHAP 2010 Alaska assessment HCI values were attributed to HUC12s. For this reason, to summarize data into HUC8s for Alaska an area-weighted average was used (i.e. the cumulative HCI score assigned to each HUC12 within a HUC8 was weighted by reach area using the formula (H1*A1+H2*A2...+HX*AX)/(A1+A2...+AX) where H = HCI score of the HUC12 and A = Area of the HUC12). To summarize data into HUC8s for the Conterminous United States and Hawaii a length-weighted average was used (i.e. the cumulative HCI score assigned to each river reach within a HUC was weighted by reach length using the formula (H1*L1+H2*L2...+HX*LX)/(L1+L2...+LX) where H = reach HCI score and L = reach length). Although data from all three assessments are summarized to HUC8s in this shapefile, it is important that values are not compared across assessment regions. More information on the three assessments can be found at the following links: Conterminous United States (http://dx.doi.org/doi:10.5066/F7B56GN1) ; Alaska (http://dx.doi.org/doi:10.5066/F7KD1VWD); Hawaii (http://dx.doi.org/doi:10.5066/F7V9863B).