Because of  the complexity of most environmental problems of an area that is influenced by urbanization where multiple sources, stressors and receptors interact which each other with nonlinear relationships it is problematic to consider one relationship at the time as in a conventional risk approach. Therefore relative regional risk ranking (RR) is applied, it summarizes the impact of multiple parameters within the region of interest considering their source and distribution(Lavers, A & Stevens, R, 2012).

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The most important parameters are grouped into sources of pollution like agriculture or industry, stressors which are the different pollutants released from the sources, the different habitats in the area of study and the end points which are the indicators of pollution such a sediment pollution in the sediments.

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The first step of the analysis is to divide the study area into smaller regions where the sources of stressors and habitats are ranked and given weighting factors. Then the interactions between sources, habitants and endpoints are evaluated allowing the relative risk of each region to be calculated and visualized.

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The results of the RR show the highest risk regions which can be used by authorities to prioritize remediation or mitigation measures(Lavers, A & Stevens, R, 2012).