Broadly Useful Technology

Niger Delta Environmental Sensitivity Index Map Developed

Esri Professional Services has been contracted to develop a widely useful set of standards and protocols for generating Environmental Sensitivity Index (ESI) maps for coastal and inland interior areas of the Niger Delta in southern Nigeria. These protocols permit the efficient, consistent development of reliable ESI maps, and the concepts and procedures these protocols define can be used in many other parts of the world as well.

Development of the protocols was funded by the Oil Producer's Trade Section (OPTS), whose member companies explore for, and produce oil within and offshore of, the Niger Delta. Nigerian regulatory requirements specify ESI mapping as part of contingency planning for oil exploration and production activities to better protect the delta's natural resources. Working with Esri is cocontractor Environmental Resource Management Limited (ERML) of Nigeria.

What Are ESI Maps?

ESI maps are basemaps that show the sensitivity of given locations or areas to a particular stress factor (such as exposure to petroleum products) on a scale from one to 10, 10 being most sensitive. The maps may contain physical and geomorphic features (e.g., shorelines), biological features, and socioeconomic features such as agricultural fields. Some ESI maps contain features of particular interest to oil spill planning and response, such as the recommended positions of booms or skimmers. The sensitivity of a given feature to a stress factor may be indicated by the color given the symbol or pattern used to represent it.

ESI Mapping Procedures Used in Nigeria

The mapping procedures used in Nigeria are based on the earlier shoreline ESI mapping techniques, but they allow inland interior areas as well as shorelines to be indexed, they use data from a wide variety of sources, and they store data in a GIS database that can be used to address questions about many different types of development.

Inland Mapping Procedures

The mapping protocols developed to generate ESI maps of Nigeria's inland areas allowed data to be included in the maps from a variety of sources, including field samples, other ESI maps, environmental impact assessments, academic studies, and remotely sensed (satellite) imagery.

The first step in mapping an area was to use the satellite imagery to divide the area into polygons. The polygon structure was then used to randomly identify a statistically significant number of field data collection (sampling) sites. For this project, the data collected at the sites was modeled to indicate the acute and persistent sensitivity (ESI) of each polygon to petroleum. All polygons of the same type were given the same ESI rank.

Shoreline Mapping Procedures

The procedure used to generate shoreline maps relied on matching existing conditions to NOAA's standard ESI classes. The process involved flying a helicopter 500 to 1,000 feet over the shoreline to be mapped; although a fixed-wing airplane could have been used, a helicopter was preferred because of its ability to fly so much slower.

The main reason for flying over the shoreline was to distinguish visibly different shoreline sections from each other on the shoreline map. Once the different sections were marked, sites where field samples should be taken could be identified. A random process was used to identify a statistically significant number of shoreline field sample sites.

Project Significance

The standards and protocols developed for this project will allow ESI maps to be created for inland interior areas anywhere in the world including harsh environments without road networks. The protocols are practical and specific enough to allow local scientists and consultants in other parts of the world to create the maps with limited training, yet sophisticated enough to satisfy existing standards for ESI mapping. This ability can lead to local companies with the capacity to perform a variety of environmental services. Finally, the procedures are practical enough to allow costs to be estimated accurately before the acquisition of map data begins.

For more information, contact Boykin Witherspoon III, Esri (tel.: 909-793-2853, ext. 1-1799; e-mail: bwitherspoon@esri.com), or Victor Ohioze Imevbore, ERML (tel.: 234-1-2625897, e-mail: ermll@linkserve.com.ng).

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