title: Identification and classification of structural soil conservation measures based on very high resolution stereo satellite data.
abstract: Land degradation affects large areas of land around the globe, with grave consequences for those living off the land. Major efforts are being made to implement soil and water conservation measures that counteract soil erosion and help secure vital ecosystem services. However, where and to what extent such measures have been implemented is often not well documented. Knowledge about this could help to identify areas where soil and water conservation measures are successfully supporting sustainable land management, as well as areas requiring urgent rehabilitation of conservation structures such as terraces and bunds. This study explores the potential of the latest satellite-based remote sensing technology for use in assessing and monitoring the extent of existing soil and water conservation structures. We used a set of very high resolution stereo Geoeye-1 satellite data, from which we derived a detailed digital surface model as well as a set of other spectral, terrain, texture, and filtered information layers. We developed and applied an object-based classification approach, working on two segmentation levels. On the coarser level, the aim was to delimit certain landscape zones. Information about these landscape zones is useful in distinguishing different types of soil and water conservation structures, as each zone contains certain specific types of structures. On the finer level, the goal was to extract and identify different types of linear soil and water conservation structures. The classification rules were based mainly on spectral, textural, shape, and topographic properties, and included object relationships. This approach enabled us to identify and separate from other classes the majority (78.5%) of terraces and bunds, as well as most hillside terraces (81.25%). Omission and commission errors are similar to those obtained by the few existing studies focusing on the same research objective but using different types of remotely sensed data. Based on our results, we estimate that the construction of the conservation structures in our study area in Eritrea required over 300,000 person-days of work, which underlines the huge efforts involved in soil and water conservation.
authors.affiliation: Centre for Development and Environment, University of Bern, Hallerstrasse 10, CH-3012 Bern, Switzerland. Electronic address: sandra.eckert@cde.unibe.ch.
authors.forename: Sandra
authors.initials: S
authors.lastname: Eckert
authors.affiliation: Asmara, P.O Box 9566, Eritrea. Electronic address: selamtesfay75@gmail.com.
authors.forename: Selamawit
authors.initials: S
authors.lastname: Tesfay Ghebremicael
authors.affiliation: Centre for Development and Environment, University of Bern, Hallerstrasse 10, CH-3012 Bern, Switzerland; Department of Integrated Geography, Institute of Geography, University of Bern, Hallerstrasse 12, CH-3012 Bern, Switzerland. Electronic address: hans.hurni@cde.unibe.ch.
authors.forename: Hans
authors.initials: H
authors.lastname: Hurni
authors.affiliation: Centre for Development and Environment, University of Bern, Hallerstrasse 10, CH-3012 Bern, Switzerland. Electronic address: thomas.kohler@cde.unibe.ch.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kohler
mesh_terms: D003247:Conservation of Natural Resources; D017753:Ecosystem; D004784:Environmental Monitoring; D058998:Remote Sensing Technology; D012987:Soil; D014881:Water Supply
chemical_list: D012987:Soil
keywords: Agricultural terraces; Digital surface model; Drylands; Object-based image analysis; Soil conservation; Very high resolution images