Use Of GPS And GIS For Preparation Of Input Maps For AGNPS Model Based On Elevation
Agricultural Non-Point Source (AGNPS) is a distributed parameter model that predicts soil erosion and nutrient transport from agricultural watersheds for real or hypothetical storms. Erosion modeling is built upon the Universal Soil Loss Equation (USLE), which predicts the long term average an...
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| Format: | Monograph |
| Language: | English |
| Published: |
Universiti Sains Malaysia
2005
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| Online Access: | http://eprints.usm.my/57566/ http://eprints.usm.my/57566/1/Use%20Of%20GPS%20And%20GIS%20For%20Preparation%20Of%20Input%20Maps%20For%20AGNPS%20Model%20Based%20On%20Elevation_Wong%20Kok%20Foo.pdf |
| Summary: | Agricultural Non-Point Source (AGNPS) is a distributed parameter model that
predicts soil erosion and nutrient transport from agricultural watersheds for real or
hypothetical storms. Erosion modeling is built upon the Universal Soil Loss Equation
(USLE), which predicts the long term average annual rate of erosion on a field slope
based on rainfall pattern, soil type, topography, crop system and management practices.
The determination of slope and its corresponding slope length is identified by slope and
aspect classes. In the present study, elevations of about 500 well-distributed points
were taken by using Global Positioning System (GPS). Root Mean Square Error
(RMSE) of these elevations was determined by comparing the elevation interplolated
from the contours. By combining the elevation of points and the contour maps, a
Digital Elevation Model (DEM) was created by using Geographical Information
System (GIS). From the DEM, various parameters such as flow direction, flow
accumulation, watershed area, slope, aspect, hillshade and LS factor map was
produced. Flow direction is determined by finding the steepest descent from each cell
while flow accumulation represent the amount of rain that would flow through each
cell, assuming that all rain become runoff. The watershed areas are described as the
surface runoff as being the locus of points within an area where runoff produced inside
the parameter will move into a single watershed outlet. Slope, aspect and hillshade are
useful in determining the LS factor. A detailed analysis for determination of LS factor
is carried out using the AGNPS – GIS interface. Results shows that the values of LS
factor vary from 0 – 111. |
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