High resolution quantification of gully erosion in upland peatlands at the landscape scale

Abstract

The upland peatlands of the UK are severely eroded, with large areas affected by gully erosion. The peatlands are important areas of carbon storage and provide a range of other ecosystem services including water supply and biodiversity all of which are negatively impacted by erosion of the upland surface. The magnitude of the gully erosion, and consequent adjustment of the peatland morphology, is such that in degraded peatlands the extent and magnitude of erosion is a major control on peatland function. Accurate mapping of gully form is therefore a necessary precondition to the understanding and management of these systems. This paper develops an approach to extracting gully maps from high resolution digital elevation models (DEMs). Gully maps of the Bleaklow Plateau in northern England were derived from a 2 m LiDAR DEM by combining areas of low difference from mean elevation and high positive plan curvature. Gully depth was modelled by interpolating between gully edges. Testing of the gully mapping and depth modelling against aerial photography, manual interpretation of the DEM and ground survey revealed that gully plan form is well represented and gully width and depth are modelled with tolerances close to the horizontal and vertical resolution of the LiDAR imagery. Estimates of gully width and depth were less reliable for gullies with total width of less than four pixels. The approach allows for the fi rst time the derivation of accurate estimates of gully extent and magnitude over large areas and provides the basis for modelling a range of processes controlled by gullying. The approach has wider applicability to mapping gully erosion in a wide range of environments.

Gully Erosion Mapping and Monitoring at Multiple Scales Based on Multi-Source Remote Sensing Data of the Sancha River Catchment, Northeast China

“…The quantification values obtained at multiple periods should be a good estimation of the magnitude of erosion-induced change [34]. Moreover, the manual digitizing of the gully edge influences the accuracy of the volumes and defining the location of the gully edge still remains a challenge [57]. …”

Carbon balance of UK peatlands: current state of knowledge and future research challenges

“…and a C content of 50% ,this equates to a particulate C loss of 136 g C m -2 yr -1 based on a realistic drainage density of 20 km km -2 and an average gully depth of 2 m (M. Evans & Lindsay 2010). This POC production rate does not, however, equate to POC flux at the catchment scale, because of in-catchment deposition of POC in gully floors and on floodplains, and because of the potential transformation of POC to DOC in the fluvial system (M. , Pawson 2008, Pawson et al 2008.…”

“…Connectivity in eroding peatland systems is strongly controlled by the balance between erosion and revegetation (M. Evans & Warburton 2005, 2007. Although there is evidence of some active revegetation of the Bleaklow Plateau (Crowe et al 2008), gully erosion is widespread and covers over 25% of the area (M. Evans & Lindsay 2010). Values of POC flux in the higher range of the reported catchments are therefore more typical of the system.…”

The role of remote sensing in the development of SMART indicators for ecosystem services assessment

“…These are of high conservation value, not only for their intrinsic habitat value, but also because they offer a wide range of ecosystem services (Table 1), including water supply, recreation, biodiversity, carbon sequestration and storage (Evans and Lindsay, 2010). However, physical degradation of peatlands is widespread, particularly in the UK, and new methods for assessing the status of these environments is required to best regulate erosion and help manage regeneration.…”