BSEN 6220 GIS LAB #5

Transcription

1 BSEN 6220 GIS LAB #5 Dustin Till 10/29/2014

2 INTRODUCTION: ArcGIS is a geographic information system for working with maps and geographic information. It is used for creating and using maps, compiling geographic data, analyzing and sharing mapped information, and managing geographic information in a database. One of the many useful tools in ArcGIS is its ability to create a watershed. This is very useful in hydrology because this is the foundation of doing hydraulic analysis of a particular area. The objectives of this lab were to delineate a watershed in ArcGIS from the data downloaded from the previous assignment, manually correct the watershed to reflect the storm water infrastructure of the area, and label the lengths of the storm water channels. This lab includes assignments 3 and 4 from the Auburn Heritage Park case study. This case study allows us to apply what we have learned in GIS to a real world engineering problem. METHODS: The project from the previous assignment was to be opened in ArcMap. The following commands are found under Spatial Analyst Tools > Hydrology in ArcToolbox and describe how the watershed was created. The first step was to fill the DEM, using the Fill command and using the DEM as the input raster. Next, the flow direction was found using the Flow Direction command and using the fill DEM as the input raster. The flow accumulation was then found using the Flow Direction command and using the flow accumulation as the input raster. The next step was to create a pour point and place it at the outlet. This was done by creating a point feature and manually placing it at the outlet. Then, using the Snap Pour Point command in the toolbox, the pour point was snapped to the cell of the highest accumulated flow within a certain distance around it. The watershed was then created using the Watershed command and selecting the flow direction raster and the pour point feature. A map was then made showing the watershed. For the next part of the lab, Auburn Campus Base Mapping and storm water infrastructure data was imported into ArcMap. The watershed was manually corrected to reflect the storm water infrastructure. This was done by converting the watershed into a polygon feature. Using the editor toolbar, the vertices of the polygon were moved, reshaping the watershed. The length of each storm water line was labeled at the end. RESULTS: The watershed was successfully made, as can be seen in map 1 in the appendix. Map 2 shows the corrected watershed to reflect the storm water infrastructure. The screenshots show the corrections I made to the watershed.

3 CONCLUSIONS: Figure 1 in the appendix shows the watershed feature before any editing. Figure 2 shows one of the corrections I made. I extended part of to the center of the road because the water from the road will flow in storm water drains that flow into the watershed. I pulled the part back that went over the road to the middle of the road because the water on the other side will get diverted away from the watershed. I am assuming the road is graded to divert the water on each half to the corresponding side. Figure 3 shows that I pulled back the watershed in that area because all of the flow in that area will be diverted out of the watershed. Figure 4 shows that I extended the bottom portion of the watershed to include the road. This is also because the water that falls on the road will be diverted to the watershed. This lab allowed me to learn how to create a watershed from a DEM in ArcGIS. I also learned how to digitize data. I learned how to convert the watershed to a polygon feature class and how to edit the feature. This allowed me to get more familiar with the editor toolbar. This lab also gave me some experience in reading base maps and storm water infrastructure maps and editing the shape of the watershed to include other sources of water that come into it besides just the natural watershed. It is easy to see from doing this lab how useful GIS is for hydrology analysis.

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