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Long-Term Hydrologic Impact Analysis

Local Government Environmental Assistance Network

L-THIA estimates changes in recharge, runoff, and nonpoint source pollution resulting from past or proposed development. It estimates long-term average annual runoff for land use and soil combinations, based on community-specific long-term climate data. In the basic model, the only inputs are: location (state and county), soil type in area where the land use will occur (available online if unknown), and type and size of land use change (e.g., 100 acres of agricultural land converted to 50 acres high-density residential and 50 acres commercial). L-THIA will generate estimated runoff volumes and depths, and expected nonpoint source pollution loadings to water bodies. Results can be displayed in tables, bar graphs, and pie charts. More advanced models are available.


Stormwater management, Water quality

The LPS Benefits Toolkit is a compilation of online calculators and tools that can be used to estimate landscape performance. The Landscape Architecture Foundation (LAF) compiles and writes descriptions of the tools in the Benefits Toolkit. LAF has no involvement in the development, review, or maintenance of the tools. If you have questions or comments on the Toolkit itself, contact us at (email hidden; JavaScript is required).

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