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TITLE A semi-quantitive spatial assessment of water erosion based on limited information using expert knowledge and real-valued observations DESCRIPTION The aim of the research is to make a semi-quantitative assessment of erosion by drawing on the knowledge of local experts and using available information on land characteristics. The method is especially useful for developing countries where quantitative data on soil loss and site characteristics is scarce, but where the rapid advance of erosion caused by water requires immediate action. The model estimates the erosion hazard by using real-valued and qualitative (local expert judgement) observations of soil loss as dependent variables, and commonly available information on site characteristics and types of land use as independent data. The estimation is adjusted for spatial and temporal autocorrelation of the variables. The study uses data from the Soil Conservation Research Project (SCRP; courtesy of Centre for Development and Environment, Bern) in Ethiopia. Numerous qualitative observations on erosion hazard were elicited via a questionnaire that was completed by nine local experts. To qualify as an expert, a person had to meet the following requirements: to understand the basic mechanisms of the soil erosion process; to be consistent in his/her assessments of erosion severity; to be familiair with the area being assessed. The experts examined well-described sites falling into six different land-use categories, and gave qualitative assessments on a scale of 1 to 5 (1=no erosion, 2=slight erosion, ...., 5=extreme erosion). The research combines expert observations with real-valued observations of soil loss (in Mon./ha-1/year-1) as dependent variables. The research uses the maximum likelihood technique to simultaneously estimate the parameters and the boundaries of the five qualitative classes. This leads to a quantitative interpretation of qualitative classes. THEMES: EROSION, ENVIRONMENTAL ENGINEERING, ENVIRONMENTAL MONITORING, SOIL CONSERVATION, SPATIAL ANALYSIS COUNTRY: ETHIOPIA Region: Afdeyu, Anjeni, Andit Tid, Dizi, Gununo, Hunde Lafto, Maybar INDIGENOUS ASPECTS The hypothesis is that local people have an institutionalized memory of the hazard of soil erosion under various land-use systems. The collection of quantitative data on the soil erosion process is tedious work that takes many years and seldom take variability in land conditions adequately into account. This is confirmed by the fact that many erosion loss studies show a poor correlation between model outcome and observations. Local experts, on the other hand, show remarkable consistency and accuracy in their assessments of erosion hazard. This can be put to good use to prevent the degradation of natural resources. SUSTAINABILITY The practice contributes to soil conservation and sustainable land-use planning. Farmers learn more about the causes and consequences of the erosion process. This leads to more sustainable practices and cultivation techniques. STAKEHOLDERS AND BENEFICIARIES The project involved Ethiopian farmers, experts in soil erosion control, and members of the scientific community. STRENGTHS AND WEAKNESSES STRENGTHS Soil erosion can be assessed on the basis of relatively little data. By combining "scientific" and indigenous assessments of soil erosion, it is possible to make an adequate diagnosis of the erosion hazard in areas where data is lacking but quick action is required. WEAKNESSES: The assessment is only semi-quantitative. The experts in this project were academically trained people who knew all the sites. Experience with farmers in Costa Rica, Chile, Indonesia and Nigeria have shown that the basic principles of soil erosion are usually not well understood. Few of the farmers even acknowledged the existence of the erosion process. IT IS CONSIDERED SUCCESSFUL BECAUSE: The methodology fills a gap in soil erosion modelling, a field that is currently dominated by process-based models that require large amounts of data but show a low correlation between model outcomes and observations. Collection of this type of data takes several years if spatial and temporal variability is to be taken into account. The methodology proposed here requires little data, and the findings can be applied shortly after the questionnaires are completed. POTENTIAL FOR REPLICATION The practice can be replicated under one main condition: Whether they are academics or farmers, the experts need to understand the basic principles of soil erosion. A model for seven countries was developed for a previous study. PERIOD: From 1996 to 2000 CONTACT PERSON: Ir. B.G.J.S. Sonneveld Vrije Universiteit Amsterdam Faculty of Economic Sciences and Econometrics Centre for World Food Studies E-mail: b.g.j.s.sonneveld@sow.econ.vu.nl ORGANIZATIONS INVOLVED: Organization that provided this information: Vrije Universiteit Amsterdam Faculty of Economic Sciences and Econometrics Centre for World Food Studies 1081 HV Amsterdam The Netherlands Telephone: 020-4449321 Fax: 020-4449325 E-mail: pm@sow.econ.vu.nl Url: http://www.sow.econ.vu.nl Cooperating organizations: University of Berne Institute of Geography Centre for Development and Environment Info Services 3012 Bern Switzerland Telephone: 0041-31-631-8822 Fax: 0041-31-631-8544 E-mail: cde_doc@giub.unibe.ch Url: http://www.giub.unibe.ch/cde/ Tilburg University Faculty of Economic Sciences and Econometrics P.O. Box 90153 5000 LE Tilburg The Netherlands

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