DETERMINING LAND DEVELOPMENT EFFECT ON

SURFACE RUNOFF USING GIS

Objectives

To assess the changes in water flow due to development

Validate USGS Data and Hydrology Analysis Tools

Study Area Location

Study Area (Continued)

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

Land Cover, Roads & Development

DEM, Roads & Development

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)

Surface Runoff Coefficient Values (VDOT)Cell Values1 Description1 Surface Runoff Coefficient4

11 Open Water 0.01

21 Developed, Open Space 0.22

22 Developed, Low Intensity 0.50

23 Developed, Medium Intensity 0.75

34 Developed, High Intensity 0.95

31 Barren Land (Rock/Sand/Clay) 0.30

41 Deciduous Forest 0.30

42 Evergreen Forest 0.30

81 Pasture/Hay 0.70

82 Cultivated Crops 0.70

90 Woody Wetlands 0.05

95Emergent Herbaceous

Wetlands0.05

Road Reclassification

Surface Runoff Before & After Development

Flow Accumulation Tool

Derived Stream Network Before and After Development

Ratio of Water Accumulation in Stream Network

Ratio of Water Accumulation in Stream Network in ArcScene

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

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

Questions?