Wilson says he's not armed with hard data, just intuition, anecdotal reports from riverfront residences, and personal experience. For example, he has seen survey monuments no more than 20 years old buried beneath eight feet of silt in the Steelhead Beach area. Others, however, are not convinced that siltation is a major flood factor in the main stem of the Russian River. There's no question about that. Whether it's being built up in some places and depleted in others, or whether it's a consistent buildup, I can't say. . . .
Sediment is somewhat like sand dunes, in that it's dynamic.
It's really hard to get a handle on it. You can't really say just because somebody's fence is covered up that the whole plain is now at that level. And you can have an increased silt load below a grading site that may sit there one winter but be completely flushed downstream and out to sea the next winter. Nevertheless, Wilson's intuitions are being confirmed in some river tributaries and floodplains, including the Laguna de Santa Rosa. The Laguna de Santa Rosa is crucial to local flood mitigation and holds as much water attenuation capacity as Warm Springs Dam.