The NWS has responsibility for forecasting flash flood potential. The development of a series of GIS data layers to aid in the development of an improved flash flood forecasting system is underway at Michigan Technological University. The particular focus of this study is the development of GIS data layers that are used to parameterize the National Flood Frequency equations, as compiled by the USGS (Water-Resources Investigations Report 94-4002). The data layers will include elevation, slope, flow direction, and accumulations along with the more state-specific parameters required in the flood regression equations for return flows ranging from Q2 to Q100. The return flow values will be used in the determination of threshold runoff, defined as the depth of rainfall excess required to cause flooding in small streams. The requirement of diverse data layers unique to each area provides a challenge in integration of data and sources. The results of this particular study will produce a coherent and complete collection of coverages for estimating flood regression values for the United States.