Identifying the erosion risk areas and efficient targeting of erosion control measures

CHALLENGE DESCRIPTION Soil erosion is a gradual process that occurs when the impact of water detaches and transports soil particles. Soil deterioration and water pollution due to erosion via runoff have become severe problems worldwide. Indeed, erosion is a serious problem both for productive agricultural land and for water quality concerns. Therefore, erosion control should be an integral part of agricultural management to maintain and improve the quality of both waters and soils. Eroded topsoil is finally transported into streams and other waterways. The subsequent sediment accumulation in the recipient waterbodies is a product of sheet and rill erosion from upland areas and, to a lesser extent, from cyclic erosion processes in drainageways. Soil erosion can occur in two stages: 1) detachment of soil particles by impacts of raindrop splash and flowing water; and 2) transport of the detached particles by flowing water. Thus, soil erosion is a physical process requiring energy, and its control requires certain measures to dissipate this energy. In addition to silting, erosion material also causes harm to the recipient waterbody by transporting nutrients, particularly phosphorus (P) which, in turn, accelerates eutrophication. Moreover, during the transport process part of the particle-bound P can be released into the form of dissolved reactive P, which is directly available to blue-green algae and thereby particularly harmful P-fraction in surface waters.

DESCRIPTION OF THE SOLUTION Key question in minimizing the sediment buildup in waterbodies is the stabilization of the sediment source by controlling erosion. Several conservation practices are usually needed to control erosion. In some situations, where the erosion is minimum, erosion control can be achieved by implementing a single practice, such as the establishment of grassed waterways. The single most effective way to control erosion is to maintain a permanent vegetation cover on the soil surface. Moreover, improving the soil infiltration rate by e.g. refurbishing the subsurface drainage, results in lower surface runoff and thus lesser erosion. Other measures that have proven effective in erosion control are no- or reduced tillage and direct sowing of annually cropped and harvested fields. Nevertheless, whatever the measure is to control erosion, the key issue is that the measures are effectively targeted. For this, modern map- and GIS-based tools offer invaluable assistance. A good example of such tool is RUSLE2015 (Panagos et al. 2015, https://doi.org/10.1016/j.envsci.2015.08.012) that can estimate soil loss at 100 m resolution based on the best available data. In Finland, RUSLE2015 has been fine-tuned to local conditions by the Natural Resources Institute Finland (Luke 2017, http://urn.fi/URN:ISBN:978-952-326-431-1). In this work, the goal is to produce a nationwide system based on Lidar-mapped (laser-scaling technique) Digital Elevation Model (DEM) for accurate erosion sensitivity maps. The maps produced by RUSLE are a good base for discussions on targeting of the measures between farmers and agriculturalists.