Adam Migliore Meyer
GEOG 591
Exercise 2: Basic Terrain Analysis and Flow Path Mapping
Basic Terrain Analysis
Battle Creek Middle Watershed DEM Histogram
Battle Creek Upper Watershed DEM Histogram
Comparison
The Middle Watershed is notably more evenly distributed in terms of elevations whereas the Upper Watershed peaks in elevations between 60 and 260 units. This makes sense as the middle watershed is further east so it would be expected to be less hilly.
The Upper Battle Creek subwatershed has generally higher elevation than Middle Battle Creek, and skewed elevation histogram, which means elevation values tend to concentrated on a certain range of value. It implies relatively uniform elevation (-1.0).
The Middle Battle Creek subwatershed has lower elevation and more evenly distributed elevation histogram. This wide distribution of heights suggests a more varied terrain (-1.0).
Battle Creek Middle Watershed ASPECT Histogram
Battle Creek Upper Watershed ASPECT Histogram
Comparison
The Upper Watershed has more northeast-facing slopes whereas the Middle Watershed has more southeast-facing slopes. Relative distributions of flat, west, and north-facing slopes are similar in the same watersheds. However when looking at the map of these slopes as opposed to the histograms, the watersheds are very similar in the geographical distributions of the different slopes. North and northwest-facing slopes tend to be in the southern portions of these watersheds while the south, southeast, and southwest-facing slopes are in the northern regions.
Flow Direction Maps
Stream Network > 1000
The Flow Direction maps appear the same between the original DEM and the filled DEM.The flow direction is very similar for the original and filled DEM, except where pits exist (-1.0). However the Stream Networks are quite different. The Filled DEM shows connected streams whereas the original DEM has some stream segments that are separated. This would be expected as the filled DEM forces the stream network to be connected by filling any pits that would otherwise fragment it.
The major pits occur in the gaps between the unfilled stream network. This is obvious as the gaps are caused by the presence of pits. Many pits occur adjacent to impervious surface edges. The impervious surfaces appear to break the stream network. The stream network does not include manmade water infrastructure such as culverts that would maintain the stream connectivity.
Pit location: Around a main stream (Battle Creek) and roads (-1.0)
By filling the pits, some streams were rerouted and became more connected (-2.0).
Thresholds for the 1000 and 500 grid cell stream networks
According to the Flow Accumulation for the filled DEM, the threshold for defining 500 grid cell stream networks is 2.23 hectares and 5.00 hectares for the 1000 cell network. There is a greater threshold for the 1000 grid cell network because this stream network requires more area in order to accumulate more water.
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.
Range of Drainage Area
The range of drainage area for defining a stream head is between 2.23 and 5.00 hectares for the main channel of Battle Creek. However, for Battle Creek tributaries the drainage area can range from 1.91 hectares to 3.72.
Late submission (-1.0)
(18/25)
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