An Internet/GIS-Based Tool to Assist Community Planners

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

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Land Use Change

• Pre-development

Post-development
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Land Use Change

• Pre-development

Post-development
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Short-term Impact
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Long-term Impact

• Dominated by runoff from smaller storm events
• Increase in surface water quantity
• Decrease in surface water quality

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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

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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

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Little Eagle Creek (LEC) Watershed
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Land Use Change in LEC Watershed
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Change in Runoff and NPS Pollution
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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

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L-THIA WWW Output

• Runoff output table summarizes land use
  information entered, curve number, runoff depth,
  and runoff volume for each year

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L-THIA WWW Chart

• Bar graphs provide runoff depth, runoff volume,
  total volume, and average runoff depth

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L-THIA WWW Chart

• All NPS pollution estimates are available in
  tabular, bar chart, and pie chart forms

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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.