An Internet/GIS-Based Tool to Assist Community Planners Bernie Engel Jon Harbor Don Jones and many others

Project Goal Create an interactive environmental analytical and educational program utilizing a WWW and GIS-based approach to answer questions associated with “urban sprawl” similar to: What will be the estimated impact on the environment due to placing a subdivision in one location vs another?

Land Use Change Pre-development Post-development

Land Use Change Pre-development Post-development

Short-term Impact

Long-term Impact Dominated by runoff from smaller storm events Increase in surface water quantity Decrease in surface water quality

Non-point Source (NPS) Pollution Originates from diffuse sources as a response to –Land use –Storm events Carried in stormwater runoff from –Agricultural lands, construction sites, urban areas Long-term impacts –Storage (lake) loss from sediment deposition –Adverse effect of chemical pollutants

L-THIA/NPS Model An overview / screening model – Quantify impact of development on long-term runoff and NPS pollution in urbanizing watersheds –Based on NRCS Curve Number (CN) technique. –User friendly, low data requirements.  Soil types  Land use / Land cover  Long-term daily precipitation record (30 years) –Identifies need for more detailed modeling. –"What-If" alternative evaluation with GIS

Little Eagle Creek (LEC) Watershed LEC Watershed Sub-basin 1 Sub-basin 2 Sub-basin 3 Sub-basin 4 Sub-basin Kilometers N EW S

Land Use Change in LEC Watershed

Change in Runoff and NPS Pollution -20% 0% 20% 40% 60% 80% RunoffNitrogenPhosphorusLeadCopperZinc

L-THIA WWW Input  State and County identify nearest weather station  Weather data queried from Oracle  User assigns land use (LU), hydrologic soil group, and projected LU area for up to three periods  Hydrologic soil group maps served with ArcView/IMS

L-THIA WWW Output  Runoff output table summarizes land use information entered, curve number, runoff depth, and runoff volume for each year

L-THIA WWW Chart  Bar graphs provide runoff depth, runoff volume, total volume, and average runoff depth

L-THIA WWW Chart  All NPS pollution estimates are available in tabular, bar chart, and pie chart forms

Summary and Conclusions L-THIA/NPS is: –A user-friendly, screening model. –Focused on long-term impacts on hydrology and NPS pollution. –Sensitive to land use change, antecedent moisture conditions, and climatic variability. –Accessible for simple “what-if” planning.