Urbanization of the Puget Sound lowlands has had a primarily negative impact on the salmon species that spawn in the surrounding streams and rivers. One of the most noticeable changes in these urbanized areas is the increase in the traditional 10-year flood being reduced to occurring once every 1–4 years. As a result of this increase in flood waters the areas where salmon lay their eggs are being washed away; this is because salmon lay their eggs just far enough beneath the bedrock to accommodate for the traditional annual flood, but due to urbanization the annual flood waters have increased and the layer of bedrock where salmon lay their eggs is washed away. This leaves the salmon with less habitat to successfully spawn on as a result. As stated above the one way to fix this problem is to use LID methods to help with the filtration process which at the same time reduces the quantity of water being put into the streams and rivers.
