Lauren Cole
UEP 232
Assignment -5
April 1, 2013
Project Data Preparation and Basic Spatial Analysis
The Town of Sudbury, MA is undergoing development changes to their town center in
order to address specific traffic and flooding issues. Sudbury is located in the greater Boston
area, and with this project, has the potential to become a leader in the implementation of
green infrastructure improvements in the New England area. GIS spatial analysis tools are
helpful for determining low points in elevation around the study area, and correspondingly
what locations will be the most suitable sites for implementing Low Impact Development
infrastructure improvements-- such as bioretention ponds, rain barrels, and catch basins. The
following research questions were used as a guide for the overall site suitability of LID
improvements:
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Research Question 1: What are the best locations to place LID infrastructure
improvements in the town center of Sudbury, MA?
Research Question 2: What are the accurate sizes of these LID infrastructure
improvements?
In order to begin the project, I set workspace settings to my Assignment 5 folder on my
H Drive. This system worked well, although I quickly learned that next time I will need both a
workflow folder AND either a “temp” or “scratch” folder to help with the organization process.
Screen Shot: Baselayer with AutoCAD File of Project Location
Next, a PDF of an AutoCAD file that contains specific location information was added to
the basemap as an overlay. As displayed in the screenshot above, the roads are color coded
into three different sections labeled: Imp_ West (Purple), Imp_ East (Green), and Imp_ South
(Yellow). These sections were determined using AutoCAD, and were based on three low points
around the study area.
Data Sets and Tools: Methodology
Data Set 1: Impervious Surface Area (vector)
Coordinate system: NAD_1983_StatePLane_FIPS_2001_Mainland
Clip/Select Tool: Overlay, Clip, Spatial Analyst, Map Algebra, and Raster Calc
Calculate Areas for Polygon: See Screen Shot, Calculated for each of the three polygons
Screen Shot: Impervious Surface Source
In order to answer the two research questions, we first needed to establish low points
and pinpoint where flooding currently occurs. This step was achieved by making site visits, and
through the use of the AutoCAD PDF file described above. Because the amount of impervious
surface has direct implications for the amount of runoff occurring in the three designated
drainage areas, I used the overlay feature to put the impervious surface rastor onto our
basemap and PDF file. In order to calculate the specific areas of impervious surface in each of
the three drainage areas, it was necessary to select three new polygons, and then use the Map
Algebra Tool, and Raster Calc Tools. The cell size for the Impervious surface raster was 1 meter
x 1 meter, so it was necessary to use the MA State Plane (m) projection.
Screen Shot: Select Tool of Project Area, with Color Coded Imp. Surface Coverage
Screen Shot: Source of Baselayer W/ Impervious Surface
Screen Shot: Calculated Area of New Polygons
Data Set 2: Elevation
Coordinate system: NAD_1983_StatePLane_FIPS_2001_Mainland
Clip/Select Tool: Overlay, Clip, Zonal Statistics as Table
Calculate Areas for Polygon: See Screen Shot
Next, the elevation datalayer was added. The cell size of elevation is 5 meters x 5
meters, which did not accurately line up with our baselayer, or impervious surface coverage.
Therefore, the new area of the elevation was not calculated. Again, the layer was clipped to the
project area. Since the study area is so small, I will need to figure out better ways of displaying
the elevation range of the area.
Screen Shot: Source of Elevation Datalayer
Data Set 3: Schools (polygon)
Coordinate system: NAD_1983_StatePLane_FIPS_2001_Mainland
Clip/Select Tool: Clip
Calculate Areas for Polygon: N/A
The project area is mostly residential, and not very densely populated. We added in the
“schools” datalayer from MassGIS, and clipped it down to our specific project area. The
projection remains the same- NAD_1983_StatePLane_FIPS_2001_Mainland.
Screen Shot: % Slope w/ One School (Turquoise dot)
Data Set 4: Parcels (polygon)
Coordinate system: NAD_1983_StatePLane_FIPS_2001_Mainland
Clip/Select Tool: Clip, Spatial Analyst, Surface Slope, Zonal Statistics as Table
Calculate Areas for Polygon: N/A
After the parcels datalayer was added, we were able to combine it with the elevation
layer, through the Zonal Statistics as Table Tool. This created a new shapefile which
represented the elevation range on each parcel. When looking at this shapefile in conjunction
with the elevation (Low points), and impervious surface, we can pick out which parcels would
be the best for installing LID infrastructure improvements.
Screen Shot: Hillshade
Screen Shot: Hillshade with Impervious Surface in Project Area
A next step could be to select for the parcels with the highest hillshade ranges with
impervious surface coverage. This could show us critical areas for LID improvements. The area
was not recalculated in this exercise, but would certainly need to be as a next step.
Screen Shot: Complete Datalayers Used