HomeMy WebLinkAbout2020 Final Flood Risk Reduction Report
Flood Risk Reduction Task Force - 2020 City Council Report
“For decades Edina took land from the water – now the water wants the
land back”
Task Force Work
The Flood Risk Reduction Task Force began meeting in July of 2019. For the past several months the Task Force has grappled with this increasingly complex issue. There are no simple
answers. Flooding issues will require a multi-pronged approach across multiple sectors within the community. Many of the actions we are suggesting have environmental benefits – which
will assist Edina in achieving Climate Action Plan goals.
BACKGROUND
Edina History
Settlers first arrived in Edina in the 1800’s and by the end of 1854 all the land in Edina had been claimed. Much of the western portion was part of the “Big Woods” – with elm, basswood,
maple and oak trees. The terrain was uneven and much of the area was poorly drained and swampy. Over time many of the hills were bulldozed, trees felled, the wetlands filled in
– and development began. Two hundred years of development has profoundly affected
storm water management, and this is a major factor in our current flooding problems.
Scope of problem
In preparation for the 2018 Comprehensive Water Resource Management Plan, Edina staff and consultants reviewed the city for areas of flooding concern... Five areas in the city were
chosen for further study – Weber Park, Concord, Halifax, Southdale First Addition Residential & Crosstown 62 & Hwy 100. Another twenty areas were screened, while fifty-four areas await
further study. In total – those areas contain - 692 homes/apartment buildings, and 863 structures.
Storm water affects Edina in a variety of ways – including overflow from natural bodies of water
to runoff from developed areas causing street flooding, damage to basements from seepage and ground water to sanitary sewer system back-ups. This is a situation affecting the health
and safety of residents and those who visit, shop, and work in our community.
Each news cycle brings yet more warnings about the damage of increasing rainfall and ground water issues – and Edina is not immune.
Contributing Factors
Increased rainfall due to Climate Change – in 2019 we received 43.17 inches of rain, 12.56 inches above average.
Rains will continue to increase, and those rains will come fast, hard and more frequently. Early snow melt compounds the flooding problem, causing additional problems for residents.
Ground water levels are rising and are difficult to measure. More residents are operating sump pumps year-round – while other residents are discovering they now need to install a sump
pump.
More development replaces vegetation and soil with impervious surfaces. Impervious surfaces
causes rainwater to runoff rather than infiltrate natural ground surface. Not only does runoff cause surface water to accumulate in land depressions, it can cause rainwater to reach
streams
faster and in greater quantities; both increasing the risk that flooding will occur sooner and more
severely than if rain were to fall on the natural ground surface.
Impervious surfaces also increase the “heat island effect” causing yet more rain.
The issue is not going away – and it’s imperative that Edina approach this situation proactively.
Reduced imperviousness results in less runoff. Any reduction in the amount of runoff translates
into increased infiltration and enhanced flood control. Limiting impervious surfaces and increasing the City’s greenspace will help reduce runoff volume, lower summertime temperatures,
and improve both water and air quality. Increased greenspace will also make our community more attractive and promote recreational activities that enhance the quality of life for those
who live, shop, visit and work in Edina.
Our Recommendations
Land Use
Regulate impervious surfaces to promote green space, trees and filtration. (Impervious surfaces have increased by 80% in Morningside over the past 50 years – exposing that neighborhood
to serious flood risk.)
As property is redeveloped add below ground water storage and above ground storage. Above ground storage (day-lighting the water) adds environmental benefits in addition to
water storage. It also serves as a “water feature” for the development.
Restrict removal of mature trees. Encourage tree planting and rain gardens
Increase green space/park areas for both temporary water storage and environmental benefits
Voluntary buy-out of homes and converting that land to temporary storage/park /green space. Allowing a rebuild at higher elevation does nothing to protect the neighborhood.
Infrastructure
Be proactive (rather than reactive) in maintenance of current system
Improve data collection to assist in planning, protection and outreach efforts
Replace aging infrastructure
At street reconstruction add larger storm sewer pipes, lower streets for temporary storage
Pumping if cost effective and doesn’t create issues for others
Education
Provide education to residents on a number of platforms to alert them to their flooding risks and how to mitigate those risks. This effort would include information on city services
including sandbag delivery, placement and pick-up, along with information on flood insurance.
Reach-out to plumbing contractors and other water mitigation businesses to inform them of Edina’s permitting and regulations regarding water issues.
Continue the Technical Support Program through Edina’s Engineering Department
to help residents reduce their risk
Ongoing
Develop a comprehensive Emergency Plan to assist residents during and after a
flooding emergency. Plan should include volunteers who could assist homeowners with
sandbagging and flood clean-up. (Service clubs such as the Edina Rotary clubs, faith
communities, etc.)
Continue to work with both watershed districts and surrounding communities to address
ongoing water issues.
Respectfully submitted:
Flood Risk Reduction Task Force Members
Richard Strong, Louise Segreto, Michael Platteter, Richard Manser, Greg Lincoln,
Roxane Lehmann, Nora Davis (Co-chair), Cathy Amlaw (Co-chair)