This study presents the development and testing of a simple calibration approach based on observed direct runoff values derived from readily available stream-gauge data available over the Internet; no complicated processing is required in the calibration process and, other than the stream-gauge data, no additional information is required beyond that used in an L-THIA model run.
L-THIA model predictions are found to be approximately 50 percent lower than actual observed direct runoff for the LEC watershed.
If the pace of land-use change or intensification is not captured in the available data, then L-THIA results should underpredict observations during periods of urbanization.
A thorough analysis of the causes of L-THIA underprediction is beyond the scope of this paper.
Impacts of urbanization on surface hydrology, Little Eagle Creek, Indiana, and analysis of L-THIA model sensitivity to data resolution.
In a GIS application, L-THIA can handle the computationally intensive task of distributing runoff calculations for numerous land use polygons over space.
Initial applications of L-THIA involved assessing the impact of land use change on groundwater recharge, and of suburbanization on runoff into a wetland in northeast Ohio (Harbor, 1994; McClintock et al, 1995).
Recent applications of L-THIA include Minner's (1998) analysis of variations in urban sprawl impacts for the major climate regions of the U.
In addition to CNs from soil and land use coverages, L-THIA runoff calculations require a long-term precipitation data set.
Runoff depth calculations were performed using L-THIA for each of the rainfall data sets.
The significant contribution of roadway areas to total runoff demonstrates that they are important areas to define in L-THIA analyses.
Using streamflow monitoring measurements near the outlet of Holetown Creek, taken during the wet season between June and December of 1992 (Delcan 1995b; Delcan 1995c), L-THIA runoff volume calculations can be compared to field measured runoff volumes.