Evaluating hydroclimatic systems across large metropolitan areas

The characteristics of Mediterranean semi-arid environments and severely altered hydrologic systems in large metropolitan areas generate numerous unique challenges for environmental modeling. This dissertation represents an effort to assess hydroclimatic systems in southern California metropolitan areas using both GIS-based and traditional hydrologic modeling with an emphasis on data and model quality issues that influence regional hydroclimatic assessments. Chapter 1 introduces the motives for modeling hydroclimatic systems and evaluating the quality of input data and various environmental models.; Chapter 2 focuses on the evaluation of the "fitness for use" of the National Hydrography Dataset (NHD). Numerous problems were identified and solutions proposed to enhance the NHD data quality and facilitate their use with the Nature Conservancy GIS tools to assess watershed conditions across the greater Los Angeles metropolitan area.; Chapter 3 utilizes spatially-distributed rainfall data and runoff measurements to examine the spatial and temporal variations in hydrologic responses and flood dynamics across the greater Los Angeles metropolitan area from 1921 to 2000. This research documents the changing flood behavior and increasing flood hazard in some watersheds due to rapid urbanization.; Chapter 4 utilizes TOPMODEL to simulate the spatial distribution of stream runoff and soil moisture content. The results show that TOPMODEL is only moderately successful when applied to semi-arid environments and that further elaboration of the model parameterization of runoff processes is required to achieve reasonable simulations in such environments.; Chapter 5 assesses a GIS-based terrain model, SRAD, in simulating one of the environmental parameters - land surface temperature (LST) - using remote sensing data at multiple temporal scales. The results show that the efficiency of environmental models varies not only with spatial scale but also temporal scale. The annual SRAD prediction provided the best agreement with remotely sensed LST, with considerably less agreement at the daily and monthly scales.; Although these chapters constitute separate research contributions, collectively they help to characterize the hydroclimatic system across large metropolitan areas. In addition, they address issues of data quality, scale, place (e.g. landscape location), and boundary conditions in GIS-based environmental modeling using new datasets from alternative perspectives.