1. DETERMINING LAND DEVELOPMENT EFFECT ON SURFACE RUNOFF USING GIS

2. Objectives  To assess the changes in water flow due to development  Validate USGS Data and Hydrology Analysis Tools

3. Study Area Location

4. Study Area (Continued)

5. Data  Bureau of Transportation Statistics (BTS) Road  National Land Cover Dataset (NLCD) 2001 – Land Cover  National Elevation Dataset (NED) 1/3 Arc Second  Digitized Land Development Data

6. Land Cover, Roads & Development

7. DEM, Roads & Development

8. Surface Runoff Calculation Q = C*i*A Q = Peak Flow (volume/time) C = Runoff Coefficient (dimensionless) i = Rainfall intensity (depth/time) A = Drainage Area (area)

9. Surface Runoff Coefficient Values (VDOT) Cell Values 1 Description 1 Surface Runoff Coefficient 4 11Open Water0.01 21Developed, Open Space0.22 22Developed, Low Intensity0.50 23Developed, Medium Intensity0.75 34Developed, High Intensity0.95 31Barren Land (Rock/Sand/Clay)0.30 41Deciduous Forest0.30 42Evergreen Forest0.30 81Pasture/Hay0.70 82Cultivated Crops0.70 90Woody Wetlands0.05 95 Emergent Herbaceous Wetlands 0.05

10. Road Reclassification

11. Surface Runoff Before & After Development

12. Flow Accumulation Tool

13. Derived Stream Network Before and After Development

14. Ratio of Water Accumulation in Stream Network

15. Ratio of Water Accumulation in Stream Network in ArcScene

16. Conclusion  New development in the study area could cause as much as 30% increase in water flow in some areas  USGS Data & Hydrology Analysis yielded reasonable results  The methodology could be used to assess the need for public agencies to proactively address future developments

17. Study Limitations & Future Study Suggestions  Proposed Grade (elevation) of New Development assumed unchanged  More recent Land Cover Data  Proposed Development is assumed as a single Land Cover Category  Effects of existing/proposed pour points are ignored

18. Questions?