Overall goal – Assess whether the proposed development of the Jarvis owned properties near Lake Monroe meet the requirements of the Monroe County zoning ordinance.
Approach:
1) Identify areas under protected zoning (ECO Zone 1 and 2, slopes > 12% and 15% respectively) within the Jarvis parcels
2) Identify which specific parcels in the newly proposed plan do not meet zoning requirements
3) Parcels that have any overlap with Area 2 can be considered Area 2 parcels. In other words if a parcel is part in Area 1 and part in Area 2 consider it a parcel that must adhere to the Area 2 rules.
Data Descriptions:
MC_Lake_Polygon - dataset with ‘fee taking’ line around which 1000ft and 2500ft buffers can be generated to find ECO Zone 1 and ECO Zone 2
Jarvis_parcels - Entire area of planned development, this is the study area boundary
Dem_sp - 10m DEM in State Plane (same as other layers)
PUD_parcels - Proposed parcel boundaries to be created in new development
Tasks and Methods for Addressing Project Goal(s)
Task 1: Create feature that represents the extent of the planned development. This will become the study area for subsequent analysis.
Methodology: The Jarvis Parcel dataset can serve as the extent and mask for raster data integration.
Task 2: Identify Area 1 and Area 2 extents
Methodology:
1) Create a data layer with a polygon edge at the fee-taking line (you’ll use the lake_polygons layer around which to create the buffers)
2) Create a 1000ft buffer around fee taking line to create Area 1 extent (ArcToolbox : Analysis Tools : Buffer).
3) Create 2500ft buffer around fee taking line.
4) Cut 1000ft buffer from 2500ft buffer to create Area 2 extent (several methods, e.g. Analysis Tools : Overlay : Erase).
Task 3: Identify areas > 12% in ECO Zone 1 (Area 1)
Methodology:
1) Create Slope dataset from DEM (Spatial Analyst main menu : Surface : Slope Or ArcToolbox : Spatial Analyst : Surface : Slope). Hint: set “extent” in Spatial Analyst to that of the Jarvis Parcels layer before creating the slope dataset to reduce processing time and dataset size.
2) Reclassify Slope dataset to areas a) greater than 12% and b) equal to or less than 12% (From Spatial Analyst Toolbar : Reclassify, or from ArcToolbox : Spatial Analyst : Reclass : Reclassify)
3) Now you need to clip the reclassed slope dataset with the ECO Zone 1 area. There are several ways to do this. Here is one method, you might want to explore others:
a. Set the Analysis Mask to the ECO Zone 1 area dataset
b. Use the Raster Calculator to basically make a copy of the reclassed slope dataset (Spatial Analyst : Raster Calculator, then just double click the name of your reclassed slope dataset so that it gets entered into the big empty window, then click Evaluate – see Raster Calculator in the Desktop Help for more info)
Task 4: Identify areas > 15% in ECO Zone 2
Methodology:
1) Pretty much the same as the methodology for Task 3. The only trick here is you need to exclude the ECO Zone 1 area from the ECO Zone 2 buffer. So make a 2500ft buffer (same method as you used to make the 1000ft buffer). Then use a tool like the Erase tool (ArcToolbox : Analysis Tools : Overlay : Erase) to eliminate the ECO Zone 1 area.
Task 5: Identify which parcels do not meet the guidelines of the Monroe County planning ordinance
Methodology:
What you need to do here is find the size of each contiguous area of < 12% slopes in each parcel (remember, each parcel in ECO Zone 1 must have > 1 acre of contiguous < 12% slope area). Vector representation is helpful here since we need patch size.
Deliverables:
1) (10 pts) Map of areas in ECO Zone 1 > 12% slope
2) (10 pts) Map of areas in ECO Zone 2 > 15% slope
3) (10 pts) Make a map of the parcels that are not in accordance with the Monroe County Planning Ordinance (Parcels in ECO Zone 1 must have at least 1 contiguous acre < 12% slope, Parcels in ECO Zone 2 must have at least 1 contiguous acre < 15% slope). This map should also show the < 12% slope area in Area 1 parcels and the < 15% slope area in Area 2 parcels.
Questions
1) (5 pts) What is the total area of < 12% slopes in the ECO Zone 1 portion of the Jarvis Parcel?
2) (5 pts) What is the total area of < 15% slopes in the ECO Zone 2 portion of the Jarvis Parcel?
3) (10 pts) Describe the algorithm used to calculate slope from a raster DEM in ArcGIS. Include a figure to help with your description.
4) (10 pts) Describe sources of error in the slope algorithm, why might the slope dataset you create not be an accurate depiction of the real world slope in the study area?
5) (5 pts) How many patches of < 12% area exist within the entire Jarvis Parcel area?
6) (5 pts) How many patches of < 15% area exist within the entire Jarvis Parcel area?
7) (10 pts) Why might your count of the number of patches in #5 and 6 not be correct representations of the real world?
8) (10 pts) Make a flow chart of the processing for this lab up through Task 4
9) (5 pts) How many parcels are not in compliance with the Monroe County Planning. To answer this provide a list of those parcels (by PUD_Code) in compliance and those out of compliance.
Ancillary note : One source of problems with pre-processing of data for this lab was that the DEM was in a different spatial reference system than the parcel data. When using any datasets derived from the parcel data (in State Plane) as a mask to subset products from the DEM (which is in UTM), the results were always empty – annoyingly there was no error message suggesting what might be the problem. The UTM version of the DEM had elevation values in meters.
So I converted the DEM to State Plane (NAD 83). But now the DEM spatial units were feet (the default units for State Plane), but the elevation values (also called z-units) were meters. Thus any slope dataset derived from this version of the DEM would be screwed up because the slope algorithm calculates rise over run, and the rise units were in meters while the run units were in feet, but the GIS didn’t know that – it just assumes the rise units and the run units are the same. So I calculated a new version of the DEM just multiplying the cell values by 3.28084 (1m = 3.28084 ft). Slope dataset derived from this version of the DEM are just fine since the rise units (elevation) are now feet, as well as the run units.