Using GIS to Synthesize the Watershed Approach into EIA

As planners and decision makers being to recognize the spatial significance of managing resources at the watershed scale, the use of Geographic Information Systems (GIS) as a main researching and teaching tool will only grow in importance. An early definition of GIS by Burrough (1986) deems it ‘a powerful set of tools for collecting, storing and retrieving at will, transforming and displaying spatial data from the real world.’ Figure 1 shows a very basic cross-sectional model of a unit watershed with different land use types.


Figure 1. Different land uses across a cross-sectional model of a watershed. (Source:

Development projects that require EIA, such as highways, factories and mines tend to impact the landscape by increasing impermeable surface cover. These impacts become compounded when there are multiple developments within the same watershed. The negative impacts of increasing impervious surface cover are noted by Barnes et. al (2002)

“The growth and spread of impervious surfaces within urbanizing watersheds pose significant threats to the quality of natural and built environments. These threats include increased stormwater runoff, reduced water quality, higher maximum summer temperatures, degraded and destroyed aquatic and terrestrial habitats, and the diminished aesthetic appeal of streams and landscapes.”

Since development impacts have cumulative effects, watershed conservation and management needs to be built into regional frameworks developed through Strategic Environmental Assessment (SEA). Regional SEA is the most appropriate framework within which to address cumulative effects when the primary goal is to influence the nature and pace of conservation and development in support of regional sustainability (Gunn and Noble, 2009). Using GIS software to better understand how these cumulative effects impact the integrity of watersheds is where I see the EIA process taking a major leap forward.

Utilization of GIS applications allows professionals to store, analyze and manipulate large amounts of spatial data on one interface. In today’s world it is not only professionals that have access to watershed data; web-based hydrological models such as Model My Watershed ( are making watershed data available to all sectors so we can collectively conceptualize how our decisions affect the world around us in terms of both space and time. Model My Watershed has developed three user-friendly applications that are free to the public and help us visualize how different land use patterns accumulate together to affect streams, rivers, lakes and entire watersheds.

Companies such as SRK Consulting have already begun utilizing GIS software to assist in the EIA process. Throughout the years of utilizing GIS applications for EIA the team at SRK has already realized some of the benefits:

“Potential risk factors may be identified upfront and presented to the client to assess the viability of proceeding with the project. This approach reduces timeframes and usually presents the client with a cost savings.”

It is the responsibility of those conducing each EIA to understand the current state of development within the watershed they are dealing with, and to understand how proposed projects will affect the integrity of entire watersheds. Anthropogenic stress on watersheds is accelerating along with human development; making GIS applications an integral tool when making more informed decisions and monitoring the impacts our development has on these vital hydrological units around the world.


Barnes, K. B., J. M. Morgan III, and M. C. Roberge., 2002. Impervious surfaces and the    quality             of natural and built environments. Baltimore, Md.: Department of             Geography and          Environmental Planning, Towson University. 28 p

Burrough, P.A., 1986. Principles of Geographic Information Systems for Land          Resources       Assessment Clarendon Press, Oxford. pp. 193.

Gunn, J., Noble, B., 2009. Integrating Cumulative Effects in Regional Strategic Environmental       Assessment Frameworks: Lessons from Practice. Journal of Environmental Assessment            Policy and Management, 11:03

Noble, Bram., 2008. Introduction to Environmental Impact Assessment: A Guide to             Principles and Practice, Second Edition. Toronto: Oxford University Press

SRK Consulting., 2013. Application of GIS in the EIA Process.


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