Assessment of gully erosion rates through interviews and measurements: a case study from northern Ethiopia

Abstract

Gullying has been widespread in the Ethiopian Highlands during the 20th century. It threatens the soil resource, lowers crop yields in intergully areas through enhanced drainage and desiccation, and aggravates flooding and reservoir siltation. Knowing the age and rates of gully development during the last few decades will help explain the reasons for current land degradation.In the absence of historical written or photographic documentation, the AGERTIM method (Assessment of Gully Erosion Rates Through Interviews and Measurements) has been developed. It comprises measurements of contemporary gully volumes, monitoring of gully evolution over several years and semi-structured interview techniques. Gully erosion rates in the Dogu'a Tembien District, Tigray, Ethiopia, were estimated in three representative case-study areas.In . The successful application of the AGERTIM method requires an understanding of the geomorphology of the study area and an integration of the researchers with the rural society. It reveals that rapid gully development in the study area is some 50 years old and is mainly caused by human-induced environmental degradation. Under the present-day conditions of 'normal' rain and catchment-wide soil and water conservation, gully erosion rates are decreasing.

Dynamics of soil erosion rates and controlling factors in the Northern Ethiopian Highlands – towards a sediment budget

“…between 2·3 and 7·4 t ha −1 y −1 (Nyssen et al, 2006c). At present, average area-specific short-term gully erosion rates are 1·1 t ha −1 y −1 .…”

“…Monitoring of gully erosion rates in the study area during three years revealed an increase of gully volume from 22 805 to 23 877 m 3 , corresponding to a specific gully erosion rate of 4·1 t ha −1 y −1 (Nyssen et al, 2006c).…”

“…In addition to human induced environmental changes, the dry years 1978-1989 also had an important impact on gully development rate ( Figure 5). It should however be noted that the environment was already more sensitive to soil erosion due to human intervention, magnifying the impact of such environmental fluctuations (Nyssen et al, 2000a(Nyssen et al, , 2002b(Nyssen et al, , 2006c. Figure 5 represents the medium-term evolution of gully erosion volume in the study area.…”

Geospatial Application in Mapping Gully Development for Effective Remediation and Control

“…It has been an endemic ecological problem of growing concern not only in the humid tropics but in many parts of the world and the literature is replete with numerous studies (Moyensons, 2003;Martinez-Cassanova et al, 2003;Martinez, 2003;Poesen et al, 2003;Valentin et al, 2005;Sirvio et al, 2004;Ronken and Bennett, 2006;Nyssen et al, 2006;Marzolff et al, 2009;Cassali et al, 2009;Poesen, 2011) Many published studies also exist on the mode of occurrence, mapping and assessment and modeling of this phenomenon in an urban environment, particularly in southeastern Nigeria (Udosen, 1998;, 2000;, 2004;, 2006;, 2008, Udosen andEssiett, 2012 ;Akpokodje et al, 2010;Essien and Okon, 2011;Essien and Essen, 2012;Nwilo et al 2011;Ehiorobo and Izinyin 2012;Jonathan and Joshua, 2013;Abdulfatai et al, 2014 amongst others). It is clear from these studies that urban expansion in most parts of Nigeria (as in other countries) leads to increase in impervious surfaces, reduces infiltration rates and consequently increased surface runoff/reduction in concentration time leading to incision and development of gullies.…”

Aplicação da dendrogeomorfologia na caracterização e datação de processos erosivos em voçorocas na região de Piracicaba, SP

“…Por tanto, considerando que a produção de células se origina no perímetro do caule, a árvore aumenta o diâmetro "de fora para dentro", o que se chama de crescimento secundário das plantas (COSTA, 2001 NYSSEN et al, 2006;POESEN et al, 2003). Recentemente, encontram-se na literatura estudos que descrevem a dendrogeomorfologia como um método alternativo com potencial para analisar a erosão em voçorocas (BODOQUE et al, 2011b;CORONA et al, 2011;MALIK, 2008;VANDEKERCKHOVE et al, 2001).…”