A watershed is an area of land that drains rainfall and snowmelt to streams, rivers, and lakes. There are thirteen (13) watersheds in Mukilteo. Twelve drain to the Puget Sound and one drains to Lake Washington. Mukilteo’s streams are small with highly developed watersheds. Many of the streams are in deep ravines cut into the underlying glacial deposits.
Rain events and watershed conditions impact stream flows. When rain falls in forested conditions, the vegetation and soils provide water storage. Land developed with roads, roofs, and other impervious surfaces impacts stream flows. Other watershed conditions that impact stream flows are geology and tree canopy. Land covered by impervious areas diminishes groundwater recharge and increases surface flows. The lack of recharge leaves streambeds dry during the summer months. Surface flows reach streams faster and with higher peaks during heavy rain events. These heavy rains scour stream beds, and undercut ravines.
Other resources to explore streams, watersheds, and the stormwater network.