Tyler Tran
Exercise 2
Figure 1. Slope histogram of upper Battle Creek.
Figure 2. Slope histogram of middle Battle Creek.
Figure 3. Aspect histogram of middle Battle Creek.
Figure 4. Aspect histogram of upper Battle Creek.
Q1. Differentiate between terrain characteristics in each of the subwatershed areas based on the DEM and aspect distributions. How are DEM and aspect distributed in each of the two subwatersheds?
The upper Battle Creek watershed is more consistent in elevation, while the middle Battle Creek watershed varies more in elevation according to the DEM histograms. Upper Battle Creek watershed has less variety in terms of slope—a large amount of the slopes in the upper Battle Creek watershed are low-sloping areas, while in the middle Battle Creek watershed, slopes vary more consistently between 0 and 26 degrees. Much of the upper Battle Creek landscape faces the northeast, while a dominant aspect for the middle Battle Creek landscape is southeast-facing.
Also the Upper Battle Creek subwatershed has generally higher elevation than Middle Battle Creek (-0.5).
Q2. Compare the stream network and flow direction maps between the original and filled DEM. What is the major difference between them?
Before the fill was performed, there were areas without connectivity in the stream flow because of the presence of pits and their disruptive effects on stream flow. After the fill, there is connectivity between the stream network without breaks in the flows. In terms of flow direction, after the fill is performed, the flow has a more distinct flow than simply flowing into a pit area.The flow direction is very similar for the original and filled DEM, except where pits exist.
Q3. Comment on the spatial distribution of depression cells. Where can you find major pits? How does filling pits affect the flow paths of this area? Why?
The spatial distribution of pits can be explained by their proximity to roads and large highways. The feature does not recognize that there are culverts and that water can flow beneath the roads, instead reading them as if the roads act as dams. Many of the pits in the watersheds are seen alongside larger roads such as Franklin Street and Cameron Avenue. Filling the pits affects the flow paths in the areas by allowing the streams to resemble a more natural flow pattern without the interruption of roads or other infrastructure features.
Pit location: Around a main stream (Battle Creek) (-1.0) and roads.
By filling the pits, some streams were rerouted and became more connected.
Any map to support your answer? (-1.0)
Q4. How many hectares is the 1000 and the 500 grid cell threshold that defines the stream heads? Use “FlowAcc_fill”, “str_1000_fill” and “str_500_fill” for the comparison.
Q5. What range of drainage area (in hectares) appears to define a stream head in this area?
Pixel counts for grid cell thresholds defining stream heads:
500: 601 pixels = 2.23 hectares
1000: 1346 pixels = 5.00 hectares
I need to see the detailed equation for your results;
For stream_500, 601 *400 * 0.000009290304 hectare = 2.233 hectares
For stream_1000, 1346 *400 * 0.000009290304 hectare = 5.002 hectares
(22.5/25)