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The Rivanna River Basin Commission, informed by the analysis and work of its Technical Advisory Committee, has determined that the primary threat to the health of the Rivanna Basin and its streams is excessive sedimentation caused by stormwater related streamflows that scour the channels.

During 2007-08, the RRBC Technical Advisory Committee consulted researchers, hydrologists, and engineers and came to the consensus that departures from the naturally occurring pathways, quantities, and rates of water flow result in the “over-arching” threat, and these departures, in turn, drive other threats to the natural system.

This "altered hydrology" results in excessive sediment in the waterways, which, in turn, adversely affects the health of the biota in the streams, literally suffocating benthic macroinvertebrates and other aquatic organisms.

Though the Rivanna also suffers from other issues (for example, contamination from e. coli and other bacteria that are harmful to human health), the Commission is focused on understanding the science of excessive flows well enough to prioritize effective conservation strategies. These are some of the important questions:

• What is the relation between stormwater flow and excess sedimentation?

• How much sediment enters our streams from overland sources? from in-stream sources?

• How does “legacy sediment” contribute to overall sedimentation in our streams?

• How can we better understand these processes so that we can target conservation and restoration activities?

• What kind of monitoring or data gathering do we need to establish baselines and show progress?
  

At the same time, the Commission is supporting its watershed partners in education and public outreach and in developing local solutions to watershed issues.

© Copyright 2009 Rivanna River Basin Commission