Watershed Based Planning

Mukilteo's streams are urban streams like most developed areas in Puget Sound. Peak winter flows and low summer flows affect the health of the streams. Heavy rains scour streams and low summer flows decrease water quality and habitat for aquatic species. Land clearing, loss of trees, and impervious surfaces associated with development lead to:

• Increased erosion in the gulches
• Degradation of wildlife habitat
• Harm to the health of streams and Puget Sound

The City is required by the Washington State Department of Ecology to create a Stormwater Management Action Plan (SMAP). A SMAP is a plan to help improve water quality in a specific watershed. The City completed the SMAP for Upper Chennault Breach Creek in 2023. The City will choose a new watershed under the 2024 NPDES Permit and develop a SMAP for that watershed on or before December 2028. The City is using the 2013 Stormwater Strategies Plan and the work done under the 2023 SMAP as the basis for choosing the next priority watershed in the city.

A watershed is an area of land that drains rainfall and snowmelt to streams, rivers, and lakes. The 2013 Stormwater Strategies Plan divided watersheds into Project Assessment Units (PAU). A PAU is a smaller watershed. The SMAP used information from the 2013 Stormwater Strategies Plan. The PAU Locations (PDF) map shows the PAUs. Find more information on each smaller watershed: Project Analysis Units (PAU) Information Maps (PDF).

The 2013 Stormwater Strategies Plan and the SMAP both evaluated watershed conditions. However, the 2013 Stormwater Strategies Plan and the SMAP have some differences. These differences might lead to a different priority watershed. The main differences are:

• Strategies Plan included watersheds outside of the City. The SMAP reviewed only watersheds within the city limits.
• The SMAP added information about future growth
• The SMAP added information about overburdened communities.
• The 2013 Stormwater Strategies Plan considered Low Impact Development as the preferred action. The SMAP will considers additional actions such as retrofits and feasibility studies for future projects to improve water quality and aquatic habitat improvements.