CEEn 414 - Civil Engineering Applications of GIS

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Characterizing the susceptibility of Park City Watershed for Erosion and Slope failure

Table of Contents

  1. Overview

  2. Data

  3. Analysis

  4. Submit

Overview

Pack City is located in Utah, northeast of Provo. It is a mountainous watershed with relatively steep slopes. The community is concerned about the possibility of hazards and environmental degradation resulting from erosion and slope stability problems.  As a GIS expert you can assess the area and select the regions within the Park City watershed that are susceptible to erosion and slope failure. You will perform the following assessments to develop a susceptibility map.

I) Erosion Assessment:

Areas inside the watershed meeting the following condition are highly susceptible to erosion.

                      Rainfall depth > = 3.0 inch and Slope >= 25° and Soil Texture = Loam or Clay Loam and land uses that have undergone human intervention.

Develop an Erosion map

Your Map should show areas with High and Low Erosion susceptibility.                  

II) Slope stability Assessment:

We will determine the factor of safety for slope failure using the following empirical equation:

Where:

C = Cohesion Factor (Use 35 for Loam and 38 for Clay Loam)

f = Friction angle (Use 25° for Loam and 27° for Clay loam)

g = Unit weight (Use 13 for Loam and 15.3 for Clay Loam)

a = Slope

Z = Depth (Use 2.75m for Loam and 2.15m for Clay Loam)

Areas with a factor of safety greater than or equal to 3.0 are SAFE and areas less than 3.0 are UNSAFE. Develop a slope stability scenario map showing the SAFE and UNSAFE regions.

You will use soil type, land use, DEM, grid rainfall and other data to perform this analysis. The following section has the links for the necessary data (Click the link to download) and projection information of each data.

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Data

DEM: Geographic Coordinate System, NAD83, horizontal units - degrees and vertical units meters

Land Use data: UTM NAD 83, Zone 12, both the vertical and horizontal units are in meters

This is land use shape file that covers the areas around the Park City watershed.

Soil Type (Soil622 and Soil613) data : UTM NAD 83, Zone 12, both the vertical and horizontal units are in meters.

Note: There are two soil files Soil622 and Soil613 which you will need to cover the watershed you are going to analyze.

This is SSURGO soil data. when you download the data, you will see two folders ("spatial" and "tabular") in both the files. The soil shapefile is in the "spatial" folder with name soilmu_a_ut622.shp and soilmu_a_ut613.shp.

Watershed polygon: It is the boundary polygon shape file in UTM NAD 83, Zone 12. (Make sure it is zone 12).

Aerial Photo: You need to download it on your own from the terraserver or other location.

Rainfall Grid: The rainfall grid is 100 year return period storm for 24 hour duration downloaded from NOAA atlas for Utah.  The spatial information extracted from its metadata is:

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.00833333
Longitude_Resolution: 0.00833333
Geographic_Coordinate_Units: Decimal degrees
Planar:
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: row and column
Coordinate_Representation:
Abscissa_Resolution: 0.00833333
Ordinate_Resolution: 0.00833333
Geodetic_Model:
Horizontal_Datum_Name: D_WGS_1972 (WGS72)
Ellipsoid_Name: D_WGS_1972
Semi-major_Axis: 6378135.000000
Denominator_of_Flattening_Ratio: 298.260000

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Analysis Guidelines

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Download all necessary data from the links above and from the internet if necessary. Then Open all the data in ArcCatalog.
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Make sure that proper projection systems has been defined for each dataset. If not, use the information given above to
define the projections.
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Create a personal geodatabase. Your geodatabase should have all the data you will use for this project. The data include:

DEM, Land use shape file, Soil type shape files, Rainfall grid, Watershed polygon and aerial photo of your watershed, and others that you may create.

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Make sure that the data frame coordinate is UTM NAD 83, Zone 12 and both the vertical and horizontal units are in meters
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There are two soil shape files necessary to cover the watershed you want to analyze. Before you convert these features to raster, do not forget to merge them together into a single file. Since you will be using the map algebra you need to reclassify the "Texture" field in the soils data to some integer value before you convert it to raster as text cannot be operated in the map algebra.

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You might need to choose the Conversion tool in the spatial analyst to convert the shape files to raster. You can either use Features to Raster or Polygons to Raster, make your selection so that it works to meet your requirement.
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Use the Watershed boundary polygon as the mask to extract the raster that fall within your watershed. Extract the DEM,  Land use, Soil and Rainfall grids.
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The rainfall data grid has cell values which are rainfall data in 1000th of an inch. Perform a suitable calculation to convert the rainfall depth to inches.
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Determine the area in the watershed with "Human Intervened land use" (From Land use grid).
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Human intervened land use are represented as:
LUCODE Land use description
11 Residential area   
12 Commercial Services 
13 Industrial                                                   
14 Transportation, Communication
15 Industrial and commercial
16 Mixed Urban or Built Up land 
17 Other Urban or Built Up land
21 Cropland and Pasture 
22 Orchards, Grooves, Vineyards, Nurseries
23 Confined Feeding Operations   
24 Other Agricultural Land 
  All other land uses are not human intervened
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You will need to create other raster datasets for Cohesion C, Unit weight g, Depth Z and friction angle f.

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Use map Algebra to determine the areas susceptible to erosion and to determine the factor of safety.

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Submit

  1. Develop an erosion susceptibility map. 

  2. Develop a factor of safety against slope stability map.

  3. Develop a combined soil hazards map that shows the overlap of the two.

  4. Develop a layout(s) showing the area that matches the above mentioned criteria for erosion and slope stability. Make your layout as professional as can be. You might want to include North arrow, Map title, graticule/grid, Inset map, Areal Photo or Topo Map, etc.

 

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Email the TA when you are finished and include a link to your assignment.

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