Simulated discharge from small watersheds before, during, and after disturbance

This study deals with the problem of inadequate historical hydrologic data, specifically the lack of good records for small watersheds. The ability to develop effective designs for projects dealing with drainage of a small watershed and to evaluate the potential impact of these designs upon the hydrology depends upon the ability to perform an interpretive analysis of hydrologic information. The lack of a historical record limits (precludes) the evaluation of potential impacts by inferences drawn from historical trends. The most obvious impact of development on a watershed is an immediate increase in stormwater runoff and surface erosion. The driving force behind these changes is rainfall. A rainfall generator was developed during the course of this study. The rainfall generator is based on a random number process and rainfall probabilities. This rainfall generator is linked with standard Soil Conservation Service techniques used for design of drainage control facilities for small watersheds. The procedures developed allow the evaluation of probable impacts of a proposed project upon the hydrology of a small watershed under seasonal conditions. Provisions are made for generation of daily precipitation (amount) on a continuous basis for any period of interest.