File #: 23-0127    Version: 1
Type: information Status: Filed
File created: 1/25/2023 In control: Utility Advisory Committee
Agenda date: 2/2/2023 Final action: 2/2/2023
Title: Stormwater Climate Planning
Attachments: 1. Excerpt of Ecology’s preliminary draft language for SWMMWW update.pdf, 2. Link to University of Washington Climate Impacts Group, 3. Staff_Presentation_UAC_Stormwater Climate Planning.pdf
Stormwater Climate Planning

Recommended Action
No action requested briefing only.

Briefing on climate projections in stormwater planning and design.

Staff Contact:
Jesse Barham, Interim Water Resources Director, 360.753.8164

Jesse Barham

Background and Analysis:
Projections for changes in the climate of the Puget Sound region have been developed by the University of Washington Climate Impacts Group over the last several years. Potential impacts to local water ways include increased winter streamflow, decreased summer streamflow, increased stream temperature, and shrinking habitat suitable for cold water fish. Key predictions that will impact stormwater management activities intended to protect local rivers, streams, wetlands, lakes and Puget Sound and the fish and wildlife that depend on them in the coming decades include increased occurrence and intensity of heavy rainfall events.

There is a high degree of uncertainty in these projections and local impacts. Staff will present a discussion of how projected changes in the coming decades may be considered in stormwater regulations, planning and design. The Washington State Department of Ecology (Ecology) has published preliminary draft proposed language in their process to update the Stormwater Management Manual for Western Washington (SWMMWW) in 2024. Staff will discuss with the UAC additional data and predictions from the University of Washington.

Climate Analysis:
The discussion will address the potential impacts of climate changes on stormwater management. No direct change in Olympia carbon emissions will result.

Equity Analysis:
Changes in climate, rainfall and related stormwater management have the potential to affect a range of demographic groups. If not planned for and managed these impacts may impact marginalized communities that do not have the resources to adapt.

Neighborhood/Community Interests (if known):
The community is concerned with climate impacts and ad...

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