There is currently a debate going on over what to do with silted in ponds. The two sides of the debate seem to be to either remove the dam and restore the river to an “unobstructed” state or to dredge the sediments out of the pond. It is unfortunate that the ponds have sedimented in so quickly! Total removal of the dam would result in the captured sediments being washed away resulting in years of very high sediment loading downstream. Removing the excess sediment would be expensive, since the pond will just silt back in. Erosion preventative land use practices and upstream stilling sediment catch basins may be a partial solution. The natural model would give some insights. In some cases the beavers continued to raise the pool level, in other cases they would leave and build upstream or downstream. The high sediment loading rates add a complex dimension to this problem. Even so, environmental decision makers must realize that the flat beaver meadow areas left after pools silt in are natural phenomena and these may provide excellent park and recreation opportunities. The stream will flow through the beaver meadow, but the dam forms a natural energy dissipating drop structure. This grassy meadow will flood during high flows, and will continue to capture sediments. The elevated water table caused by the meadow will still contribute to charging the lower stream during periods of drought. The full subsurface reserve would still exist and the silted in pond volume will now be part of the subsurface reserve. The exact hydrology of this system varies, but beaver dams and meadows always increase the subsurface water charge. This concept is shown in the illustration below.
Meadows are another unique ecosystem adding to biovidersity. Meadows have rich moist soil and lush vegitation. Many flat river basins are actually beaver meadows. The spanish term for a meadow is “Vegas.” A photograph of a newly forming beaver meadow is shown below.