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{{Short description|Environmental impact assessment method}}
The '''Leopold matrix''' is a qualitative [[Engineering:Environmental impact assessment|environmental impact assessment]] method developed in 1971 by Luna Leopold and collaborators for the USGS.<ref name=":0">{{Cite journal|last1=Leopold|first1=Luna Bergere|last2=Clarke|first2=Frank Eldridge|last3=Hanshaw|first3=Bruce B.|last4=Balsley|first4=James R.|date=1971|title=A Procedure for Evaluating Environmental Impact|url=http://pubs.er.usgs.gov/publication/cir645|journal=|location=Washington, D.C.|pages=19|via=U.S. Geological Survey}}</ref> It is used to identify and assign numerical weightings to potential environmental impacts of proposed projects on the [[Earth:Natural environment|environment]].<ref name=":0" /> 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 [[Earth:Environmental impact statement|impact reports]].<ref name=":0" />  
[[File:Leopold Matrix Magnitude and Importance Locations.png|thumb|291x291px|'''An Example Showing the Location of Magnitude and Importance Values in a Leopold Matrix Cell''']]
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.<ref name=":0" /> In practice, only a select few (25-50) of these interactions are likely to be of sufficient importance to be thoroughly considered.<ref name=":0" /> 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.<ref name=":1">{{Cite book|last=Noble|first=Bram F.|url=https://www.worldcat.org/oclc/1153262303|title=Introduction to environmental assessment : a guide to principles and practice|publisher=Oxford University Press|year=2020|isbn=978-0-19-902889-4|edition=4|location=Don Mills, Ontario|oclc=1153262303}}</ref> 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.<ref name=":0" /> 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 [[Engineering:Land development|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 [[Earth:Erosion#Water|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.<ref name=":0" /> In this case, an impact of significant magnitude may not actually be important to the environment in question.

== Strengths ==
As outlined by the original authors, the matrix provides a structured framework for practitioners of environmental impact assessment to systematically rank potential significant environmental cause-and-effect relationships.<ref name=":0" /> A structured approach avoids the downsides of less organized ad hoc approaches to impact prediction in which impacts can be either underestimated or completely overlooked.<ref>{{Cite book|url=https://www.adb.org/publications/environmental-impact-assessment-developing-countries-asia|title=Environmental Impact Assessment for Developing Countries in Asia|date=1997-12-01|publisher=Asian Development Bank|language=en}}</ref> Additionally, the grid format allows for a visual display of results that can be easily understood by policymakers and the public.<ref>{{Cite book|last=Kumar A. Rathi|first=Arjun|url=https://www.worldcat.org/oclc/1246578449|title=Handbook of Environmental Impact Assessment : Concepts and Practice.|date=2021|isbn=978-1-5275-6789-4|location=Newcastle-upon-Tyne|oclc=1246578449}}</ref><ref>{{Cite book|last=Carley|first=Michael|url=https://www.worldcat.org/oclc/1102806782|title=Social impact assessment and monitoring : a guide to the literature|date=2019|publisher=Routledge|others=Eduardo S. Bustelo|isbn=978-0-429-30630-3|location=London|oclc=1102806782}}</ref> The matrix is also capable of expanding and contracting based on the scope and environmental context of any given undertaking, rendering it functional for both large and small-scale projects.<ref name=":1" /> Finally, it is beneficial to practitioners that the tool can be applied at various temporal stages of the environmental impact assessment process.<ref name=":3">{{Cite book|last=Mareddy|first=Anji Reddy|url=https://www.worldcat.org/oclc/990802553|title=Environmental impact assessment : theory and practice|date=2017|isbn=978-0-12-811238-0|location=Kidlington, Oxford|oclc=990802553}}</ref>

== Criticisms ==
One of the fundamental downfalls of the method is the lack of criteria or standard methods for assigning magnitude and significance values which may lead to subjective judgements.<ref>{{Cite book|url=https://www.worldcat.org/oclc/319298237|title=Methods of environmental impact assessment|date=2009|publisher=Routledge|others=Peter Morris, Riki Therivel|isbn=978-0-203-89290-9|edition=3|location=London|oclc=319298237}}</ref><ref>{{Cite book|last=Rogers|first=Peter P.|url=https://www.worldcat.org/oclc/185040378|title=An introduction to sustainable development|date=2008|publisher=Earthscan|others=Kazi F. Jalal, John A. Boyd|isbn=978-1-84977-047-7|location=London|oclc=185040378}}</ref><ref>{{Cite book|last=Mushtaq|first=Basharat|url=https://www.worldcat.org/oclc/1154563861|title=Environmental management environmental issues, awareness and abatement|date=2020|publisher=Springer|others=Suhaib A. Bandh, Sana Shafi|isbn=978-981-15-3813-1|location=Singapore|oclc=1154563861}}</ref> In the same vein, the method has also been identified as lacking the ability to facilitate any degree of public involvement, primarily due to the subjective value judgements of the user.<ref>{{Cite book|last=J.|first=Barrow, Christopher|url=http://worldcat.org/oclc/45860278|title=Social impact assessment : an introduction|date=2000|publisher=Arnold|isbn=0-340-74217-8|oclc=45860278}}</ref> Another potential pitfall is the sheer size of the matrix with a total of 17 600 items of information potentially being analyzed.<ref>{{Cite journal|last1=Clark|first1=Brian D|last2=Chapman|first2=Keith|last3=Bisset|first3=Ronald|last4=Wathern|first4=Peter|date=1978|title=Methods of Environmental Impact Analysis|url=https://www.jstor.org/stable/23284628|journal=Built Environment (1978-)|volume=4|issue=2|pages=111–121|jstor=23284628 |issn=0263-7960}}</ref><ref>{{Citation|last=Wood|first=Christopher|title=Screening and Scoping|date=2000|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/9781118685570.ch4|work=Environmental Assessment in Developing and Transitional Countries|pages=71–84|publisher=John Wiley & Sons, Ltd|language=en|doi=10.1002/9781118685570.ch4|isbn=978-1-118-68557-0|access-date=}}</ref> The size of the matrix has also been criticized as being too detailed for some projects while simultaneously being too imprecise for others.<ref>{{Cite book|url=https://www.worldcat.org/oclc/38294546|title=Environmental impact assessment and environmental auditing in the pulp and paper industry.|date=1996|publisher=Food and Agriculture Organization of the United Nations|others=Oreade, Food and Agriculture Organization of the United Nations. Forest Products Division|isbn=92-5-103794-9|location=Rome|oclc=38294546}}</ref> In terms of direct content, the chance of double-counting certain impacts is also present.<ref>{{Cite book|last=Bhatnagar|first=K. C.|url=https://www.worldcat.org/oclc/435376013|title=Environmental management : new directions for the 21st century|date=2009|publisher=Global India Publications|isbn=978-93-80228-11-2|location=New Delhi|oclc=435376013}}</ref><ref>{{Cite book|last=Graham Smith|first=L|title=Impact Assessment and Sustainable Resource Management|publisher=Taylor & Francis|year=2014|isbn=9781317900108}}</ref> The matrix has further been identified as being highly biased toward [[Earth:Biophysical environment|biophysical]] impacts making the social impacts of a given project difficult to assess.<ref name=":3" /><ref>{{Cite book|last=MacKinnon|first=Aaron J.|url=https://www.worldcat.org/oclc/1020318892|title=The application of science in environmental impact assessment|date=2018|others=Peter N. Duinker, Tony R. Walker|isbn=978-1-351-17344-5|location=Milton Park, Abingdon, Oxon|oclc=1020318892}}</ref> Of the impacts that are covered, the matrix is seldom capable of taking into consideration secondary or cumulative impacts which are often significant considerations in environmental impact assessment.<ref name=":2">{{Cite book|last=Glasson|first=John|url=https://www.worldcat.org/oclc/60559255|title=Introduction to environmental impact assessment|date=2005|publisher=Routledge|others=Riki Therivel, Andrew Chadwick|isbn=0-415-33836-0|edition=3|location=London|oclc=60559255}}</ref><ref>{{Cite book|last=Hira|first=Anil|url=https://www.worldcat.org/oclc/52216286|title=Development projects for a new millennium|date=2004|publisher=Praeger|others=Trevor W. Parfitt|isbn=0-275-97502-9|location=Westport, Conn.|oclc=52216286}}</ref><ref>{{Cite book|url=https://www.worldcat.org/oclc/1051352223|title=Planning and design of engineering systems|date=2018|others=G. C. Dandy|isbn=978-1-351-99129-2|edition=2|location=[Place of publication not identified]|oclc=1051352223}}</ref> Another area that the method can be deficient in is having a mechanism capable of distinguishing between long-term impacts and short-term impacts.<ref>{{Citation|last1=Kassim|first1=Tarek A.|title=Environmental Impact Assessment: Principles, Methodology and Conceptual Framework|date=2005|url=http://link.springer.com/10.1007/b98263|work=Water Pollution|volume=1|pages=1–57|editor-last=Kassim|editor-first=Tarek A.|place=Berlin/Heidelberg|publisher=Springer-Verlag|language=en|doi=10.1007/b98263|isbn=978-3-540-00268-0|access-date=2021-11-15|last2=Simoneit|first2=Bernd R. T.|editor2-last=Williamson|editor2-first=Kenneth J.}}</ref><ref>{{Cite book|url=https://www.worldcat.org/oclc/1242466181|title=Environmental management : issues and concerns in Developing Countries|date=2021|others=Pradip K. Sikdar|isbn=978-3-030-62529-0|location=Cham|oclc=1242466181}}</ref><ref>{{Cite book|last=Eccleston|first=Charles H.|url=https://www.worldcat.org/oclc/311307339|title=NEPA and environmental planning : tools, techniques and approaches for practitioners|date=2008|publisher=CRC Press|others=CRC Press|isbn=978-1-4200-0781-7|location=Boca Raton|oclc=311307339}}</ref> Due to the presentation of completed matrices, the method has also been identified as treating interactions as though they are certain to occur, with no consideration of probability.<ref name=":2" />

== Examples of Leopold Matrix Implementation ==

* Gonabad landfill; a study conducted to evaluate the environmental effects of a municipal waste landfill site.<ref>{{Cite journal|last=SA|first=Sajjadi|date=2017|title=Environmental impact assessment of Gonabad municipal waste landfill site using Leopold Matrix.|url=http://www.ephysician.ir/index.php/browse-issues/2017/2/586-3714|journal=Electronic Physician|volume=9|issue=2 |pages=3714–3719|doi=10.19082/3714 |pmid=28465797 |pmc=5410896 }}</ref>
* Vojvodina ecological network; an assessment of the influences of anthropogenic factors on an ecological network (salt steppes, marshes, etc.).<ref>{{Cite journal|last1=Kicošev|first1=Vesna|last2=Romelić|first2=Jovan|last3=Belić|first3=Anđelka|last4=Marinić|first4=Ivo|last5=Panjković|first5=Biljana|date=2015|title=Assessment of the influence of anthropogenic factors on elements of the ecological network in Vojvodina (Serbia) using the Leopold matrix|url=http://www.doiserbia.nb.rs/Article.aspx?ID=0354-46641500097K|journal=Archives of Biological Sciences|volume=67|issue=4|pages=1209–1217|doi=10.2298/abs150303097k|doi-access=free}}</ref>
* [[Place:Karbala|Karbala]] water projects; a study on seven drinking water treatment facilities based on physio-chemical properties.<ref>{{Cite journal|last1=Al-Nasrawi|first1=F A|last2=Kareem|first2=S L|last3=Saleh|first3=L A|date=2020-01-17|title=Using the Leopold Matrix Procedure to Assess the Environmental Impact of Pollution from Drinking Water Projects in Karbala City, Iraq|journal=IOP Conference Series: Materials Science and Engineering|volume=671|issue=1 |pages=012078|doi=10.1088/1757-899X/671/1/012078|bibcode=2020MS&E..671a2078A |s2cid=213207854 |issn=1757-899X|doi-access=free}}</ref>
* Binh Thuan desertification; an assessment of the potential desertification effects and subsequent impacts on socio-economic conditions and water availability.<ref>{{Cite journal|last1=Hai|first1=Le Trinh|last2=Gobin|first2=Anne|last3=Hens|first3=Luc|date=2014-01-02|title=Uncovering causes and effects of desertification using a Leopold matrix in Binh Thuan Province, Vietnam|url=https://doi.org/10.1080/10042857.2014.883052|journal=Chinese Journal of Population Resources and Environment|volume=12|issue=1|pages=57–67|doi=10.1080/10042857.2014.883052|s2cid=128966076 |issn=1004-2857}}</ref>

==See also==
* {{annotated link|Engineering:Environmental impact assessment|Environmental Impact Assessment}}
* {{annotated link|Engineering:Strategic environmental assessment|Strategic Environmental Assessment}}
* {{annotated link|Social:Social impact assessment|Social Impact Assessment}}
* {{annotated link|Philosophy:Impact assessment|Impact Assessment}}
* {{annotated link|Risk assessment}}
* {{annotated link|Precautionary principle|Precautionary Principle}}
* {{annotated link|Medicine:Healthy development measurement tool}}

==References==
<references />

{{DEFAULTSORT:Leopold Matrix}}
[[Category:Environmental science]]

{{Sourceattribution|Leopold matrix}}