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This repository contains the set of Python scripts that were developed to create a custom ArcGIS geoprocessing tool to assit the Cumberland County (Pennsylvania) Department of Public Safety with their SARA Tier II reporting.

The goal of this repository to is to provide a starting point for other government agencies that perform SARA Tier II reports. As your organization may use different datasets in your analysis, the tool would need to be updated to reflect those changes.

While this tool was created for a specific purpose, the scripts could be refactored to perform a proximity analysis for a location that is defined by latitude/longitude.

Analysis Summary

  1. Create a projected point feature from the user provided latitude/longitude coordinates.
  2. Create a multi-ring buffer feature class around the point feature. The user provides the buffer distance(s) and units.
  3. Perform an analysis to see if any building polygon features that intersect the point feature intersect a FEMA floodplain.
  4. For each ring in the multi-ring buffer feature class, clip a U.S. Census Block dataset. A proportional population and number of households is calculated for each ring in the multi-ring buffer feature class.
  5. For each ring in the multi-ring buffer feature class, select any vulnerable facilties that intersect the multi-ring buffer feature. If any features are selected, they are exported to a Microsoft Excel file.
  6. A project map (.mxd) is created from a template file. The point feature and multi-ring buffer feature are added to the map. The map is saved, and exported to a .pdf file.

Summary of Tool

This tool consists of eight (8) Python scripts. is the script that the custom tool is built from. The other seven scripts are modules which are imported into or other modules.

This tool collects parameters from the ArcGIS tool's form using the arcpy.GetParameterAsText() method. All inputs are required.

  1. SARA Name (string) - the name of the SARA facility.
  2. SARA Address (string) - the street address of the SARA facility.
  3. PATTS ID (string) - an unique identifier for each SARA facility.
  4. Chemical Info (string) - information about the chemical(s) being used for the analysis
  5. Latitude (double) - the latitude in decimal degrees of the SARA facility.
  6. Longitude (double) - the longitude in decimal degrees of the SARA facility.
  7. Distances for Risk Radius (double; multiple values allowed) - the distance(s) for each risk radius buffer.
  8. Risk Radius Units (string; drop-down list) - the units for the risk radius buffers
  9. Output Directory (folder) - the folder location where the data and files for the analysis are generated.

A helper module that handles reporting errors to the user. It lists the error message, line number, and file in which the error occurs. It is based upon a custom geoprocessing tool developed by Esri's Jake Skinner.

This module takes the user entered latitude/longitude coordinates and re-projects it to State Plane coordinates. It then creates a multi-ring buffer on the projected point layer, using the buffer units and distances provided by the user. The module is called within this module.

The projected point feature class and multi-ring buffer feature class are returned from the module for use in other parts of the analysis.

A helper module which tests whether a building polygon feature related to the user submitted latitude/longitude coordinates intersect a FEMA floodplain. It is used within the module. A Select By Location analysis is performed between the point feature class (generated in and a building polygon layer. If the building polygon layer contains the point feature class, then the selected building polygon layer participates in a select by location analysis against the FEMA floodplain layer. A message is written to an output text file as to whether the site intersects or does not intersect a floodplain.

This module calculates the proportional population and number of households within each risk radius using U.S. Census block-level data. A ratio is created between the original area of the Census block feature and the post-clip area. This ratio value is used to calculate the proportional population and number of households.

For example, if a Census block feature contains 1,000 people and 500 households, but only 50% percent of it's original area is within a risk radius, then the assigned population would be 500, and the assigned number of households would be 250. This is currently my best solution to deal with aggregrate data like Census blocks. I am well aware of the limitations and assumptions being used.

The population and number of households for each risk radii are also written to the project text file that is generated in the user-defined output directory.

A helper module which converts a feature class to a Microsof Excel file. It is used within the module. It performs a select by location between the featureLayer and intersectLayer parameters. If records from the featureLayer are selected, the layer is exported to Excel. If not features are selected, a warning message is provided to the user.

This module is used to identify any vulnerable facilities within each risk radii. I am not aware of any standard as to what a vulnerable facility is. Our Emergency Management office defines these, and they have changed over time. A Select By Location analysis is performed against each vulnerable facility within each risk radii ring. If features are selected, then the selected features are exported to a Microsoft Excel file. The module is used to assist with this process.

Vulnerable Facilities

  • Daycares
  • Health & Medical Sites (excluding pharmacies)
  • Schools (public & private)
  • Mental Health Intellecttual & Development Disabilities (MHIDD) Facilities
  • Public Shelters
  • SARA Facilities (hazmat)
  • Emergency Response & Law Enforcement Facilities
  • Hydrography (NHD polylines)
  • Municipalities (sub-divisions of counties)
  • Counties
  • Natural Gas Facilities

This module uses a template map document (.mxd) and creates a project map document for the analysis. Information about the SARA site (name, address, and chemical information) is updated on the map. The projected point and mulit-ring buffer layers are added to the map, and symbolized using layer (.lyr) files. Lastly, the map is exported an Adobe Reader file (.pdf).


ArcPy scripts for a custom geoprocessing tool to estimate population and identify vulnerable facilities in proximity to SARA tier 2 facilities








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