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Model land use change between the years of 1978 and 2010 within the study boundaries.
Determine the percentage of land uses (forest, open space, and urban space) in this area within these time periods.
Calculate the change in land uses and storm water runoff over this time period.
Evaluate the usefulness of this method for use in an urban area
Methods (Data Collection)
DEM (Digital Elevation Model) obtained from City of Salisbury GIS Division
Soil Data obtained from Rowan County
Aerial Imagery from 1978 obtained from City of Salisbury GIS Division
Satellite Imagery from 2009 obtained from City of Salisbury GIS Division
The following data was required to complete the project:
1978 Aerial vs. 2009 Satellite Imagery Zoomed
Methods (Incorporate data into GIS)
DEM was used to create data involving flow direction , and flow accumulation to create stream channels.
Imagery was digitized and clipped to create two land cover maps for 1978 and 2009.
Soil Data was clipped for the study area and grouped in to Hydro groups ( A-D ) (A = low runoff potential and D = higher runoff potential.)
4 inch Rainfall map was created using flow direction and accumulation techniques.
The Curve Number Runoff ( CNR) Equation was used to show runoff totals for both time periods
The higher the CN , the higher potential for runoff
Methods: (CRN) Equation
Q = (P - I a ) 2
P - I a + S
Q = runoff
P = precipitation
S = potential maximum soil moisture retention after runoff begins
I a = initial abstraction, basically the amount of water before runoff , such as infiltration , or interceptance by vegetation.
I a is the percentage of S: I a = 0.2S
Q is then:
Q = (P - 0.2S ) 2
(P + 0.8S)
The Curve Runoff Number , CN is then related:
S = 1000 - 10
Results Land Use Statistics for the year (1978) Forest = 53% Open Space = 40% Urban = 7% Flow Accumulation at Innes St. point from a 4 inch rainfall: 78,592 Land Use Statistics for the year (2009) Forest = 50 % Open Space = 35% Urban = 15% Flow Accumulation at Innes St. point from a 4 inch rainfall: 92,131 Land Use Change between 1978 and 2009 Forest = -3% Open Space = - 5% Urban = +8%
Project Significance and Encountered Issues
Projects like this one can be significant because they reinforce what is already known about the impacts of urbanization on storm water runoff.
Knowledge has been used in the development of storm water retention ponds.
From this example, downstream development which is near the floodplain has been removed over the years and discouraged .
This next slide shows a couple issues I encountered: My evaluation is that the CNR Method would work better for areas with greater change in elevation and less urbanized environments.