By Guillaume Mauger, Research Scientist, Climate Impacts Group, UW Seattle
Sea level rise isn’t the only factor driving changes in flood risk for Washington State: many rivers and creeks in the region are projected to see higher peak flows in the future. This is especially a concern in estuaries, where the combined changes in river flow and sea level could dramatically change the outlook for flooding.
Rivers flood because of high flows, of course, and there are two principal ways that climate change could affect the size and frequency of flooding. The most well-known is by decreasing the amount of snowpack. Mountain snow acts as a reservoir, holding back water in winter and releasing it in summer. As temperatures rise, storm events bring more rain and less snow. Much of that excess rain goes directly into our rivers, leading to bigger floods. The other major effect is the intensity of our rain events – research has only recently begun to quantify how our big storms might change in the future, and that modeling generally shows that those storms will bring more rain. More rain means larger floods. This is all summarized in a nice infographic, developed by the Skagit Climate Science Consortium, or SC2.
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