Ilir Bejleri
Paul Zwick
Andy Lyons

A GIS Analysis Tool To Determine The Environmental Impact Of Transportation Corridors

To improve the environmental review process and project development of transportation projects in the State of Florida, the Governors' office and an intra-agency group including several federal and state agencies have developed the Environmental Screening Analysis, a methodology and process aimed to screen proposed transportation corridors for potential environmental impacts. Based on the proposed guidelines, Florida Department of Transportation and University of Florida have implemented Environmental Screening Analysis Tool, a semi-automated wizard driven GIS-enabled application. Through and integration of ArcView and MS Access and based on a very large standardized state-wide GIS database maintained at the University of Florida, the application analyses any proposed corridor and the adjacent areas in any part of Florida for major environmental flaws. The tool provides quantitative indicators to measure the impact severity and maps highlighting impacted areas, all in web-ready HTML format. In addition it allows for customization of criteria and tests, addition of new criteria, sharing of criteria and tests between users and comparative analysis of multiple corridor alternatives. Current research directions of expanding the application to analytically determine the least environmental impacted path and an attempt to implement the tool on the web are briefly discussed.

Keywords: GIS Analysis, Transportation, Environmental Evaluation, Environmental Impact, GIS Application

Introduction

In response to the Transportation Equity Act for the 21st Century passed by Congress in 1998 (US DOT 2000), the Florida Department of Transportation is making great efforts to streamline the process of transportation planning and environmental review of highway projects (FDOT 2000). In collaboration with University of Florida, FDOT had developed a large statewide geographic digital database and a number of software tools to streamline project development and implementation. The focus of this paper is to describe one of the tools called Environmental Screening Analysis Tool designed to assist transportation planners of MPO-s and FDOT in their environmental impact evaluation of transportation projects.

Environmental Screening Analysis

Environmental Screening Analysis consists of guidelines to identify major issues of proposed transportation projects early on in the planning phase that can be consulted and resolved by the appropriate stakeholders before additional resources are invested into the project. This methodology has been developed by an inter-agency taskforce led by the Florida Governor’s office in 1999 (Governor’s Office, State of Florida 1999). The Environmental Screening Analysis consists of several criteria that seek to identify a number of potential impacts that may be caused by the transportation projects including:

- Contemplation of the study with federal goals and plans
- Intersection or adjacency of the corridor with conservation lands
- Intersection or adjacency with critical and strategic habitat
- Intersection of adjacency with 100-year significant flood plains
- Consistency of the drainage alterations with the watershed management plans
- Impact on significant wetlands
- Impact on significant natural resources
- Access to barrier islands or access to Coastal High Hazard Areas
- New access or increased capacity to non-urbanized areas

In addition to the above criteria, FDOT Environmental Management Office added a number of other criteria that address the potential impact of the proposed transportation corridors on the community. Some of these criteria include:

- Breaking of the community cohesion by dissecting community boundaries
- Reduction of access between various community activities
- Impact on special populations such as elderly, low income, minority etc
- Impact on ‘community significant’ areas
- Impact on the economic stability of the community

Other important additions to this category are the criteria that concern potential impact on historic features including:

- Historic and archaeological sites of Federal, State or local significance
- Officially designated State Historic Highways
- Historic bridges
- Parks, wildlife refugees

Based on the criteria above the GeoPlan Center at the University of Florida developed for FDOT the Environmental Analysis Screening Tool (ESAT), a GIS-enabled application that implements the screening guidelines. ESAT is developed as a tool that would assist transportation specialists to quickly identify the potential significant impacts early on in the planning phase of the project and prioritize the subsequent detailed analysis.

GIS and Environmental Impact Evaluation

Geographic Information Systems (GIS) have been now proved as an effective technology to be successfully used in the environmental evaluation of transportation projects. GIS brings together a rich compilation of data about the study area to guide design decisions (Frerichs W. N. and West J. Rl, 1998). In addition GIS provides a number of analytical functions to analyze the data and produce new information. These capabilities have been used in a number of examples in transportation projects especially to identify the least impact path. Sadek at al. (1999) use GIS and a multi-criteria system to evaluate a number of transportation alignment based on topographic, urban, environmental features and geometric design with emphasis on geotechnical characterization. Similar approach has been used to identify the best road alignment that minimizes the environmental impact on fauna, flora, soils, water, air and people (Zura and Lipar 1995). HDR Engineering used numerous variables including historic sites, wetlands, stream crossings, historical accident data and vertical profiles to locate a feasible road corridor through the Appalachian Mountains of North Georgia. (Gilbrook M. J. 1998).
The strength of the GIS tool presented here consists in the use of a standardized, generic methodology that can be applied to any new highway transportation project in the State of Florida. In addition, this tool makes use of a large statewide geographic database and comes with a simple user-friendly interface. The focus of this paper is to describe the structure, implementation and usability of this application.

Structure

The core block of the application is the ‘Test’ (figure 1).

Figure 1. "TEST" structure.

A ‘Test’ is a function that allows identifying the spatial relationship of the proposed corridor with the geographic data layer. For example to answer one of the criteria questions ‘Are there wetlands of regional significance in the corridor area?’ the application calls a GIS function that determines if an intersection exists between the corridor layer and the wetlands layer. If the result is positive a numeric indicator that quantifies the impact is reported. In the example above it will be the number of acres of the wetland inside the corridor. The application employs the following spatial operations to measure the impact:

- Crosses/adjoins polygon features
- Crosses/adjoins grid (raster) features
- Comes within X meters of point features
- Crosses/adjoins line features

For the criteria that are not affected by the spatial relationship a map is provided for visual inspection.
Attribute queries are used as filters to analyze only that part of the database that applies to the test. For example in identifying the ‘significant wetlands’ in the corridor, first the wetlands layer is queried on the appropriate attribute to filter out uplands and those wetlands that are not significant.

To determine whether the outcome is critical or not two default values are used as thresholds. If the outcome is higher than the highest value than the impact is determined to be severe. For values between the thresholds the impact would be moderate and below the smaller threshold value the impact is insignificant.

Another variable defined with the ‘Test’ is the desired output that include the map, legends, labels etc.

Any criterion can contain one or more tests. The criteria are grouped in categories. For any given study the criteria category, the criteria, the project corridor, the tests for each criteria and the parameters for each test are variables and can be combined in various ways to allow maximum flexibility.

Implementation

Database component
The implementation of the application required two main components: the geographic data and the software. To fulfill the objective of enabling the tool to evaluate any new proposed road corridor in any area of Florida the data component had to be available statewide. For this task it was decided to use the Florida Geographic Data Library, a standardized rich compilation of 250 layers of geographic data, both vector and raster (Esri shapefiles and GRID-s), aerial photography and satellite imagery available on CD-ROM and on the web for the entire state of Florida. FGDL is developed at the GeoPlan Center of University of Florida. For more information see http://www.fgdl.org

Software component
For the implementation of the application the development team selected to use ArcView 3.1 or higher as the base GIS software and used ArcView’s Avenue programming language for the automation of the analysis and the interface customization. The application was packaged as an ArcView extension, a solution that would allow the maximum use and deployment flexibility. All the spatial analysis described in the application structure above have been automated including both vector and raster geographic data. The later requires Spatial Analyst, Esri’s extension for GIS raster data.

The complex interrelationships of the various organizational and functional components such as the study area, corridors, criteria, tests, test parameters etc., were compiled in tabular form using MS Access database system. The Entity Relationship diagram is fully normalized allowing maximum expansion flexibility and application control integrity. The inherent link of forms and tabular data in Access allows simpler and quicker customization. In addition, the decision to store these relationships in a RDBMS instead of a flat file system was also made to anticipate a sound web implementation of the application, which is currently under development.

The link between ArcView and MS Access is established by using the ODBC and Dynamic Data Exchange (DDE) technology supported by both ArcView and Access.

The outcome of the analysis is automatically created in two commonly used formats: MS Word and HTML. Using DDE, ArcView sends to MS Word all the results including text and graphics. The Word report can then be printed and used in addition to other project documentation. The report in HTML format is written programmatically using Avenue and the files are organized in a structure suitable for web publishing.

Usability

The environmental screening application can be loaded in a new or an existing ArcView project. Initially the analyst can screen digitize the road alignment of interest using an image as a reference. There are two kinds of images that can be used: 1 meter color Digital Orthophoto Quarter Quads or the black and white 2 m aerial photography.
A buffer tool provided with the extension allows the analysts to create the actual road corridor with the desired width. In cases when the road centerline is already available as shapefile or CAD drawing it can simply be loaded in the project and the buffer tool can be used to create the corridor.
Once the corridor has been created or loaded, through a wizard-based interface the analyst would select the group criteria of interest, the desired test for each criterion and parameters for the output report format.

All the details of the analysis are already setup in tabular form in Access.

Default parameters are stored for most of the analysis components. However, the analyst can change most of these parameters. The interface for modifying the analysis settings is provided in Access forms. Using a menu (figure 2) the user can select to change the type of analysis, proximity area, buffer sizes for affected areas, impact threshold values for low, medium and high degree of impact, datasets to be used, query expression that selects the attributes of interest and a number of parameters for map display and report making (figure 3). To enable users share their customized analysis the application contain an export/import feature available in Access interface (figure 2).

Figure 2: Access ESAT Menu Figure 3: Test Input Access Form

The final report contains the study area map, an executive summary, and the results of each test (figure 4) with the numeric indicator of the size of the impact, details for the attributes of features impacted and a traffic light graphic icon showing the severity of the impact. The HTML report is build with a left and right frame for easy navigation whereas the MS Word report is built in a traditional linear fashion.

State Road 7 Extention - Option 1
There is 868.5 acres of wetland areas within 500 ft of the corridor. Source: National Wetland Inventory.

Figure 4: A page from the report generated by ESAT; The numeric indicator is shown on top; The map with the traffic light indicating the level of severity is shown in the middle; The details of the analysis are shown at the bottom. Note that the map shows only a part of the 9 miles long corridor whereas the indicators apply to the whole 9 mile long corridor. The example take from a pilot study area in Palm Beach county, Florida.

Conclusions and Future Directions

The environmental screening analysis tool described here is a GIS-enable application designed to help transportation planners identify potential environmental and community impact early in the planning phase. Although ESAT generates numeric indicators and spatial outputs which can support other studies, ESAT is not intended to replace traditional, more rigorous methods of environmental impact evaluation. Its main purpose is to identify fatal flaws or potentially significant impacts and prioritize where additional analysis will be required. The questions that can be examined by ESAT depend on the nature of the available data. Both environmental impacts as well as socio-economic impacts and jurisdictional issues can be studied if appropriate data is available. Any type of question whose answer depends in part on a geographic relationship with the proposed corridor may potentially be integrated into ESAT. Multiple alignments can quickly be analyzed by ESAT identifying advantages and disadvantages for each alignment. ESAT is designed to allow sharing of data and impact methodology especially because of the integral use of statewide data library. The local data for a new test can be packaged with the analysis definition and can be exported and imported between ESAT users.

On the flip side of this flexibility, one must remember that the quality of results produced by ESAT will only be as accurate and up-to-date as the data used. For example, statewide habitat coverage digitized at 1:100,000 may be only accurate to within 500 feet. This may be fine for large-scale analyses, but may result in a high margin of error when trying to determine habitat impacted by a 220-foot wide corridor. Likewise, a census coverage that is ten years out of date will likely underestimate any demographic measures for community impact assessment.

Currently the research team is focused in extending ESAT from a screening tool into a decision support system with the ability to determine the least impact alignment based on the user criteria priority. This would allow identifying alternative routes that minimize the environmental impact according to the user special conditions. A second current effort is directed into web enabling of both the current screening capabilities and the best route selection extension. A number of map server technologies have been explored so far and the present effort is focused in using Esri’s ArcIMS as a technology that allows the flexibility that ESAT requires to be ported to the web.

Acknowledgements

The development team would like to acknowledge for guidance and support: Leroy Irvin, Manager, Environmental Management Office, FDOT and Robert Crim, P.E. State Project Development Engineer Environmental Management Office, FDOT.

References

Florida Department of Transportation, 2000. “Developing Efficient Transportation Decision Making Processes”, Environmental Management Office. http://www.dot.state.fl.us/emo/esp/esp.htm

Frerichs W.N., West J.R., "Using GIS to streamline and improve highway planning and design", Roadway Design, CE NEWS online, November 1998

Gilbrook, M.J., "Finding the Appalachian Scenic Corridor"

Governor's Office, State of Florida, 1999. Guidelines to Address Secondary and Cumulative Impacts in the Planning and Project Development Process. Tallahassee, Florida.

Sadek, S., Bedran, M., Kaysi, I., 1999. “GIS platform for multi-criteria evaluation of route alignments,” Journal of Transportation Engineering, Vol. 125, No. 2, March/April 1999. pp. 144-148.

US Department Of Transportation, 2000. “Environmental Streamlining”, Federal Highway Administration – Planning, Environment and Real Estate Services. http://www.fhwa.dot.gov/environment/strmlng.htm.

Zura, M., Lipar, P. 1995. “The road and traffic environmental impact statement and optimal room layout selection,” in 15th Annual Environmental Systems Research Institute User Conference Proceedings. Environmental Systems Research Institute. Redlands CA. http://www.Esri.com/library/userconf/archive.html.

Author Information:

Ilir Bejleri, Ph.D.
Assistant Professor and Applications Development Manager for GeoPlan Center
Department of Urban and Regional Planning
University of Florida
431 Architecture Building
Gainesville, FL 32611
Phone: (352) 392-0997 ext. 432
Fax: (352) 392-3308
Email: ilirbeu@yahoo.com

Paul Zwick, Ph.D.
Associate Professor, Department Chair and GeoPlan Center Director
Department of Urban and Regional Planning
University of Florida
431 Architecture Building
Gainesville, FL 32611
Phone: (352) 392-0997 ext. 427
Fax: (352) 392-3308
Email: paul@geoplan.ufl.edu

Andrew Lyons
University of California at Berkley
Email: filijee@yahoo.com