Sedimentbudgetar

Sedimentbudgetar, or sediment budgets, are quantitative assessments of the balance of sediment within a defined system, such as a watershed, river reach, delta, or coastal cell. They summarize how much sediment enters, leaves, and is stored over a period, providing a framework to understand landscape evolution and sediment-related processes.

Inputs include erosion of upstream and within-system sources (rock weathering, landslides, bank retreat), tributary sediment supply, coastal cliff and dune erosion, and, in some cases, human inputs such as mining spoil or dredged material. Outputs include export to downstream basins or the ocean, removal by reservoirs or dredging, and deposition within the system (storage). Storage changes occur in floodplains, deltas, dunes and banks, reservoirs, and subsurface burial.

The sediment budget is often written as a mass-balance equation: dS/dt = I − O, where I is the rate of sediment inputs and O is the rate of outputs. In a near-steady state, dS/dt is small (I ≈ O). Positive dS/dt indicates net storage (aggradation), while negative dS/dt indicates net erosion or burial of existing storage.

Methods combine measurements of suspended-sediment and bedload fluxes, sediment yield estimations for watersheds, and geospatial data from bathymetry, lidar, satellite imagery, and dredging records. Dating techniques and stratigraphic analysis can help reconstruct past budgets. Uncertainties arise from nonstationarity, scale dependence, and unaccounted sources or sinks.

Applications include river and coastal management, sediment budgeting for reservoir and habitat planning, flood-risk assessment, and evaluating the impacts of land-use change and dam construction on long-term sediment dynamics.