Leopold_matrix
Leopold matrix
Environmental impact assessment method
The Leopold matrix is a qualitative environmental impact assessment method developed in 1971 by Luna Leopold and collaborators for the USGS.[1] It is used to identify and assign numerical weightings to potential environmental impacts of proposed projects on the environment.[1] It came as a response to the National Environmental Policy Act of 1969 which was criticized for lacking adequate guidance for government agencies on how to properly predict potential environmental impacts and consequently prepare impact reports.[1]
The system consists of a grid of 100 rows representing the possible project activities on the horizontal axis and 88 columns representing environmental factors on the vertical axis, for a total of 8800 possible interactions.[1] In practice, only a select few (25-50) of these interactions are likely to be of sufficient importance to be thoroughly considered.[1] Where an impact is expected, the appropriate cell of the matrix is split diagonally from the top right corner to the bottom left corner in order for the magnitude and importance of each interaction to be recorded.[2] The magnitude (from -10 to +10) is inserted on the top-left diagonal and the importance (from 1 to 10) is inserted on the bottom-right diagonal.[1] Measurements of magnitude and importance tend to be related, but do not necessarily directly correlate. Magnitude can be measured more tangibly in terms of how much area is affected by the development or how severely, however, the importance is a more subjective measurement. While a proposed development may have a large impact in terms of magnitude, the effects it causes may not actually significantly affect the environment as a whole. The example given by author Luna Leopold is of a stream that significantly alters the erosion patterns in a specific area, which may be scored highly in terms of magnitude but may not be necessarily significant, provided the stream in question is swift-moving and transports large amounts of sediment regardless.[1] In this case, an impact of significant magnitude may not actually be important to the environment in question.