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.