Identification and classification of structural soil conservation measures based on very high resolution stereo satellite data

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

An extended riparian buffer strip concept for soil conservation and stream protection in an agricultural riverine area of the La Chevrotière River watershed, Québec, Canada, using remote sensing and GIS techniques

The implementation of riparian buffer strips in agricultural areas is regarded as a means to protect watercourses against runoff water carrying sediments and contaminants. In the field, riparian buffers are usually dimensioned to meet the minimum width required by policies and regulations. In the case of the province of Québec, Canada, regulation stipulates a width of 1-3 m in agricultural watersheds. However, such small riparian strips offer little protection, especially during the spring-snowmelt period when the soil is saturated, infiltration is low, vegetative cover is poor and soil erosion and runoff are the dominant hydrological processes. In this study, high-resolution, remote sensing, raster-based information is used to evaluate an extended riparian buffer strip concept with variable widths of 5-120 m to assess soil erosion and to convert agricultural riverine areas into soil and water conservation areas. For a studied watershed of 108 km² in Québec, this would enable reducing soil erosion in riverine areas from 361 to 1.0 t year⁻¹ (1.9 to 0.005 t ha⁻¹ year⁻¹), and thereby reducing soil erosion at the watershed scale by 40% (calculated with the Revised Universal Soil Loss Equation, RUSLE). The extended riparian buffer strip concept would require the conversion of 7% of the 29 km² of agricultural land

Evidence of topographic disequilibrium in the Subarnarekha River Basin, India: A digital elevation model based analysis

Cratonic areas experience complex process-response changes due to their operative endogenic and exogenic forces varying in intensity and spatiality over long timescales. Unlike zones of active deformation, the surface expression of the transient signals in relatively tectonically stable areas are usually scant. The Subarnarekha River Basin, in eastern India, is a prime example of a Precambrian cratonic landscape, overlain in places by Tertiary and Quaternary deposits. A coupled quantitative-qualitative approach is employed towards deciphering tectonic and geological influences across linear and areal aspects, at the basin and sub-basin scale. Within this landscape, the transient erosional signatures are explored, as recorded in the disequilibrium conditions of the longitudinal profiles of the major streams, which are marked by a number of waterfalls at structural and lithological boundaries. Mathematical expressions derived from the normalized longitudinal profiles of these streams are used to ascertain their stage of development. Cluster analysis and chi plots provide significant interpretations of the role of vertical displacements or litho-structural variations within the basin. These analyses suggest that a heterogeneous, piece-meal response to the ongoing deformation exists in the area, albeit, determining the actual rate of this deformation or its temporal variation is difficult without correlated chronological datasets.by Shantamoy Guha and Priyank Pravin Pate

Tempestitic shell beds formed by a new serpulid polychaete from the Bajocian (Middle Jurassic) of the Central High Atlas (Morocco)

92Nie dotycz