As of late January 2024, the year's second significant rainstorm has been forecast for later in the week and following. In Santa Cruz County we have several streams and rivers whose flow will be increased. Here I have some images of streamflow in the San Lorenzo River over a few timespans, to illustrate our need for flood readiness in Felton and Santa Cruz.
A key warning signal for coming high flow is when the flow after a given rainstorm doesn't drop back to the level it was before that storm. When a succession of storms continues to "ratchet up" up the minimum, it means that the soils in the watershed are more saturated and the creeks and streams feeding into the river are still flowing higher than usual, so the river's "main stem" fills more quickly.
A concerning observation for this year and the coming rainstorm is that the minimum dry season flow in 2023 was far higher than in previous years, no doubt still being fed by the ample water from the early 2023 storms. Why is this concerning? It means that this season the river will reach high flows with less new rainfall - or, put another way, new rainfall this season won't have to be as much to bring flood danger. This is especially the case for Felton Grove, but deserves attention in downtown Santa Cruz. And of course many other streams and rivers in our region can expect the same phenomenon.
