SEDIMENT YIELD MODELING BY GROUPED RESPONSE UNITS

A geographic information system (GIS) is interfaced with a geomorphic- based hydrologic and sediment transport model. The modeling strategy m akes use of the ''grouped response unit'' concept whereby land classes are identified within homogeneous regions and used as hydrologic and sediment response units. The computational units are defined on the ba sis of homogeneity of topography and soil characteristics using freque ncy histograms of relevant parameters as objective criteria. The model is then applied to each land class within the computation units. The GIS/model interface is accomplished on an interactive basis in order t o allow the user to have some decision-making authority. The methodolo gy is demonstrated in detail and six years of runoff and sediment data are simulated for a watershed in western Puerto Rico. GIS functions a re used to demonstrate how the data may be analyzed under various opti ons the planner or manager may desire.