Practical implications of quantifying ancient sedimentation rates in lakes

Excerpt

Sediments stored in lakes represent a valuable archive that can be used to reveal the erosion history of watersheds. A portion of the soil that is moved down gradient during runoff events is deposited in lakes, and the rate at which sediment accumulates should be proportional to the rate of erosion from the surrounding land. The ability to calculate historical sedimentation rates opens several opportunities for improved understanding and management of watershed processes. Examples include quantifying changes in erosion and deposition rates caused by anthropogenic or natural shifts in land use or by climate change.

Erosion is difficult to quantify at the watershed scale because of the large degree of spatial and temporal variation in erosion rates. Changes in slope, vegetative cover, soil compaction and composition, and a host of other variables can result in a wide range of erosion rates over distances of a few meters. Erosion rates can likewise vary significantly with changes in rainfall intensity and time since the last precipitation event. Lakes receiving this variable influx have a normalizing effect that allows long-term changes in sediment accumulation rates, and thus changes in erosion at the watershed scale, to be identified. Changes in erosion at scales smaller …