This guidance tool highlights the key elements for decision making to prioritize investments for sediment management at a landscape level. The introduction provides an overview of the challenge that accelerated erosion and sediment pose. The next section highlights the applications of sediment modelling and its value-add to specific sectors such as Agriculture, Hydropower and Water Supply. A section on Sediment modelling explains the various tools that can be used individually or together to gather the best data and model the process of sediment loss and erosion at a landscape level. The next section of the guidance note presents a phase wise approach to prioritizing investments to manage sediment at a landscape level. It provides guidance for practitioners on undertaking a thorough planning process, preparing a sediment budget and finally undertaking a prioritization exercise to plan investments in the landscape based on the findings of the sediment budget.
Erosion is the wearing away of rocks, geologic and soil material via water, wind or ice (glaciers) – particulate matter is formed and dislodged as a consequence. Sedimentation is the process in which this dislodged particulate matter or sediment is carried from its point of origin by natural or human- induced processes and deposited elsewhere on land surfaces or in water bodies. In the context of Agriculture accelerated erosion of fertile top-soil is a challenge and measures to reduce erosion are often explored by agronomists. On the other hand, the deposition of sediment in reservoir environments such as those created by Hydropower projects or in lakes can cause problems in the storage capacity or lead to flooding. Sediment can also erode hydropower turbines. Often, hydrologists and water engineers are more interested in these off-site effects of erosion - measuring and addressing sediment deposition. This guidance tool is designed for basin level planning for watershed projects that may have one or multiple objectives such as agricultural productivity, hydropower efficiency or water quality, thus the terms erosion and sediment are both used.