Workshop Notes: Stormwater Workshop: Stormwater Climate Resilience in Western Washington
10-02-19
Projected Changes in Extreme Precipitation (Presenter: Guillaume Mauger, UW Climate
Impacts Group) & Climate Change Impacts on Stormwater Facility Sizing (Presenter: Jeff
Burkey, King County, [email protected])
Summary of Study Results
Recent analysis by the King County Department of Natural Resources and Parks, University of
Washington Climate Impacts Group, and Washington State Department of Ecology suggests that
projected changes in heavy rain events may require larger BMPs. In short, a suite of BMPs evaluated for
changes in rainfall at Sea-Tac were shown to need larger capacities to mitigate future projections of
rainfall using current design standards. However, the identified relative increases needed were variable
and counter-intuitive at times when considering soil infiltration capacities, levels of development, and
sources of rainfall. Moreover, aside from the orographic effect of the Cascade Mountains on rainfall in
the Puget Sound, a casual review of downscaled rainfall in a few other locations within King County
suggests results may be different than what has been evaluated using projections associated with the
Sea-Tac area. Additional research is needed to develop a more robust set of scenarios and verify these
results.
What We Will Need and What Is Currently Being Done
The 10:45 –11:45 portion of the workshop examined current jurisdictional activities and needs related
stormwater management climate resiliency (facilitator: Peter Holte, [email protected])
Participants provided input into topic areas, processes and research needs that will help
stormwater utilities prepare for and adapt to climate change impacts.
James Rufo Hill, Seattle Public Utilities detailed how Seattle is currently using rainfall data and
information on rainfall partners to better manage their system and conduct preemptive
maintenance ahead of large storms.
Several participants shared actions their utilities are taking in response to climate change. This
included: the cities of Seattle, Bellevue, Sammamish, Shoreline and Renton, and Snohomish and
Kitsap Counties.
Participants offered the following topics as potential areas that need further exploration:
Continued support for regional investigations and discussion on stormwater resiliency in the face
of climate change
o Refinement, monitoring and verification of current research
o Increasing the number of modeling simulations; use “crowd sourcing” to support this
work {see related attachment from Jeff Burkey]o Additional forums or methods of sharing information to address technical, policy, and
operational considerations
Workshop Notes: Stormwater Workshop: Stormwater Climate Resilience in Western Washington
10-02-19
o Integrating climate considerations into Stormwater Action Monitoring (SAM) efforts
Communication with various stakeholders—this includes developing support for stormwater
resiliency by learning how to listen to and talk to:
o Utility rate payers (the public)
o Elected officials
o State and Federal Agencies
o Each other
Looking beyond changes in stormwater volumes
o Changes in water temperature—impacts on habitat
o Climate impacts that increase (or decrease) the effects of pollutants of concern in
natural waterways, fish or wildlife
o Maintenance and operation considerations
Climate immigration– Lara Whitely Binder provided context for this concern. She noted that
studies have found that people’s decision to move from one area to another are driven by
numerous variables. At this point in time, movement of large numbers from one area to another
within the US as a consequence of climate change does not seem to a pressing concern.
Emergency response and mapping of frequently flooded areas
o How will Flood Insurance Rate Maps (FIRMs) change in response to climate change?
o Identifying and working with vulnerable populations in floodways
o Matching the need to keep people out of harm’s way vs. the need for more housing
stock (Seattle)
Performance monitoring of stormwater BMPs
o “We should make sure that our models correctly predict performance” and base our
response to climate change relative to how facilities are actually performing in the field
o The role of rainwater harvesting as mitigation measure and the regulatory framework
associated with this BMP
The process for including updated standards to stormwater manuals—
o How will Ecology and other manual authors respond to data and work with manual
users
o A representative from Ecology a) reminded that they supported Jeff Burkey’s work, and
b) said the right now they are in “information gathering and listening mode” with
respect to climate change impacts and resiliency
Tackling jurisdictional actions
o Track stormwater climate resiliency work by individual jurisdictions so that we leverage
information, resources and actions
Workshop Notes: Stormwater Workshop: Stormwater Climate Resilience in Western Washington
10-02-19
Learning from others
o Are there lessons to be learned from the studies and actions conducted by other types
of utilities—for example what might we learn from drinking water utilities?
Breakout Session Notes
The following items were listed on the flip charts during the 11:40 – 12:25 breakout session. The items
are provided here “as is” (i.e., as written onto the flip charts). Questions? Contact Peter Holte, City of
Redmond ([email protected]) or the listed breakout station session facilitators.
1. How do we maximize existing asset performance given the uncertainties around resizing for
climate change? (facilitator: Jessica Engel, King County, [email protected])
Retrofits the existing assets
o Prioritize, reverse engineer
Understand flows coming out of the retention and detention
o Look at capacity
o Categorize performance and prioritize what needs most attention
Proactive maintenance before storm hits
Developers should be aware of these issues
Monitoring/stay on top of maintenance
WSDOT- don’t retrofit to design standards
Asset management- wrap in climate change?
Look at criticality factors- what assets prioritized first?
o Build in climate change as a part of ranking
Look at other subdivision, model current performance and bring up to current standards
considering future conditions
Sediment management
Knowing where you will have flooding- change use of area to avoid development or certain
uses+ allow it to flood
What do we do with info to get at implementation if there is no requirement from ECY yet?
Model in WWHM with new rain data, what modifications to control structures to assist with
capacity
Analysis of current facility to see if capacity issues exist and has to increase capacity now
Change law (?) + outlaw structures in ponds to ensure pond is holding water during storms
and not bypassing
Allowing certain infrastructure like pushing lots to flood or use the roads for storage
Land use changes
o De-pave
o Building up instead of out
Workshop Notes: Stormwater Workshop: Stormwater Climate Resilience in Western Washington
10-02-19
2. How do we build more capacity and support for addressing climate change impacts on
stormwater management? (facilitator: Peter Holte, City of Redmond, [email protected])
Policy: how to incorporate climate impacts into all decision making (like equity)
o Increase cultural value on climate resiliency planning
ex: all CIP must include climate considerations
o Appeal to ‘action orientated’ or ‘green’ identity of elected/citizens
o Find specific items/ actions aka ‘SMART’ objectives
o Bringing reforestation/ other non-gray infrastructure into capital projects trade-offs
(ex: meandrins vs. ponds)
o Include new staff to consider climate change
o Look at lessons learned/ planning processes of other utilities (wastewater/water)
o Consider how to get beyond the growth mitigation mindset
Potential Action:
o Talk with council about climate change
o Education others about system loading of CO2 in atmosphere
o ‘sell up’ to decision makers about climate change, provide real solutions
o Quantify uncertainty for projects (ex: Seattle Ballard tunnel)
o Present as risk management
Look at Denmark- Cloud Burst program
Look at cost of damage in large events to leverage funds and allow decisions
makers to make long-range decisions
o Be transparent about uncertainty, it could leverage elected desire to decrease
uncertainty
Lacey Drinking Water example: sold an odd/even watering policy to avoid infrastructure
development
3. What are the technical assessment and science needs that we should be prioritizing?
(facilitator: Jeff Burkey, King County, [email protected])
If you had to move forward now with the information you have today, what would you need
to make that happen?
Awareness- increase understanding trust. Limiting on models
o “Stress testing”
Increase social science + elected. Delays now increase public understanding
What connects the public?
How does 2080 designs impact now?
Restoration design
What landscape features are more sensitive?
How about geographic/time for future? Trade space for time?
Performance monitoring
Cost/ benefit/ now vs. later
Workshop Notes: Stormwater Workshop: Stormwater Climate Resilience in Western Washington
10-02-19
o Area and land, increase floods, local services
o Instead of more GCM/ WRF
o How do we use current observations?
Evaluate zoning change
Hi-Flo bypass to receiving waters
Water quality? Nutrients?
Fund wholistic way, cross departments, multilevel solution
Water support-shift from show rain. Keep at source (Infiltrate)
4. How much do you plan for now versus later given the tradeoffs between costs and uncertainty
(and what actions would you pursue)? (facilitator: Lara Whitely Binder, King County,
[email protected])
Need actions that have clear benefits now (multi-use/benefits facilities) allows you to
make that higher investment now
Present performance as a non-binary decision (ex: 70% probability now, 50% prob in future).
Prompts discussion of what else can be done now (SPU Experience)
Actions that allow for incremental progress while maintaining options
Look for the small & (extras) that could go a long way if done now (keep options open)
more integrated planning
Need to get better data that help people understand the scope and scale of the problem in
ways that connect with residents (and in flood frequency)- 100 years 25 years
o Need to ask the question to start with often not as big of a change as you think
How would an X% increase affect Y
More scrutiny on life-cycle cost analysis and benefit/cost assumptions. May be more benefit
than we realize; may be discounting the future too much (discount rate)
Would need to present quantifiable costs and risks for different actions. Have to show the
investment now will offset future costs
o Supports because changes idea
Don’t frame decision as 30% bigger because rain 30% more; think about and talk about
ranges (where are we on the bell curve now vs later?)
Projected flood maps  tools to help visualize the changes and related implications
Need equitable ways to fund and account for decision costs