Evaluating Connectivity Among Habitat Patches Using NetMap

To assess the role of stream connectivity in fish population structure, we need data and metrics that appropriately quantify connectivity and population structure. As this symposium illustrates, there are many options. In dealing with connectivity, for example, we can look at flow distance and network structure, or at the distribution of habitat patch types, sizes, proximity, and persistence. Likewise, we have options in assessing human impacts on connectivity: loss of longitudinal connectivity by barriers, added connectivity via canals and roads, loss of lateral connectivity with floodplains and hillslope processes. In many cases, there are data with which to characterize these attributes, but the amount of data processing required to create appropriate metrics can be daunting. This is where NetMap comes in. NetMap is a data analysis system, currently linked with ArcGIS, to use available digital data to characterize geomorphic controls on fluxes of water and sediment in a river system. NetMap uses a linked network and raster data structure that maintains information at the finest grain, but can integrate over any scale. NetMap is used for a variety of habitat assessments (e.g., intrinsic potential), but has not been applied (as far as I know) for assessments of connectivity. I will illustrate how tools in NetMap might be used to define connectivity metrics and how these can be linked to other data sets for further analyses.