Long-Term Impact Assessments

Community planners, developers and citizens of a community should be aware of the long-term impacts of landuse change on their environmental resources. L-THIA, Long-Term Hydrologic Impact Assessment, is designed to help these people to quantify the impact of land use change on the quantity and quality of their water. This tool uses the land use and a soil characteristic from the user along with thirty years of precipitation data to determine the average impact that a particular land use change or set of changes will have on both the annual runoff and the average amount of several non-point source pollutants. For those unfamiliar with the hydrologic (water related) impacts of land use change this tool along with the supporting documents will hopefully give the user enough information to start asking questions about land use changes in their area.

There are several input screens for spreadsheet L-THIA, which are available from the side bar to the left.

For residents of EPA Region 5 states, there is a GIS version which automatically categorizes landuse and soil based on your location using Google Maps (tm).

[ Online watershed delineation (OWL) and LTHIA ]

For those new to L-THIA and land use planning Basic Input is a good place to start. There are eight choices for land use types which most land uses fall into. For those familiar with land use planning terms or need to describe a custom land use, Detailed Input gives more land use options. The fourteen choices for land uses includes 6 lot sizes for residential housing and an option to define a custom land use. After using the Basic Input for a few analyses, a user would be able to use the Detailed Input.

Additional information about long-term impacts of land use change and L-THIA can be found in the Documentation section (click on the words in the navigation bar to the left). Along with background information about L-THIA there is information on how to interpret you results and what you can do to minimize the impacts of land use change.