A set of GIS tools has been developed to analyze the impacts of roads on forest watersheds from USDA Forest Service road inventory information. A database schema was developed to represent the road inventory in a structured way. The sediment production for each road segment is calculated from slope, length, road surface condition and flow path vegetation and used to calculate accumulated sediment load at each drain point and sediment input into each stream segment. The impact of road drainage on terrain stability is calculated using an infinite plane slope stability model based on slope and contributing area with the added effect of road drainage on specific discharge. Drain point gullying is also predicted using slope and contributing road length at each drain point. The final function in the tool set analyzes the fragmentation of fish habitat due to the potential blockage of fish passage at stream crossings.
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