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HomeMy WebLinkAbout190924 Meeting 7 Staff Report September 24, 2019 Flood Risk Reduction Strategy Task Force Jessica Wilson, Water Resources Coordinator, Ross Bintner, P.E., Engineering Services Manager, Martha Allen, Water Resources Intern Flood Risk Reduction Strategy Meeting 7 Flood Risk Reduction Strategy Task Force Draft Report in advance of Council Meeting Why a Flood Risk Reduction Strategy? Since its incorporation in 1888, flooding issues have been a challenge within the City of Edina. In 1908, the land upon which the City was built was described on a USGS map as “an ill-drained, glaciated area”. Contemporary residents all around the City of Edina have experienced flooding issues from creeks, lakes, basins, and neighboring properties. In recent years, increasing knowledge around stormwater management and regulation of the floodplain have improved the ability of decision-makers to recognize issues and make tough decisions; however, there is currently no comprehensive strategy that defines or prioritizes issues and there remains a gap between the level of service expectation and reality. Feedback on the urgency of this issue and the desire for transformational change was iterated by Council on multiple occasions and was incorporated into the 2019 Comprehensive Water Resources Management Plan (CWRMP), to be addressed through development of a Flood Risk Reduction Strategy. In order to ensure that this strategy was representative of the needs of Edina residents, a volunteer Task Force was formed to seek community input and insight. Task Force members first met in June of 2019 and have been meeting bi-weekly for several months in answer to the charge presented by City Council. Their charge was to “Provide recommendations to inform a Flood Risk Reduction Strategy (FRRS) to be considered for adoption by the City Council and incorporation as a major amendment to the City’s Comprehensive Water Resources Management Plan.” Task Force members very quickly expressed their agreement with council that this issue is of great importance to the safety and stability of their communities and to the City as a whole. Members represent homeowners with a range of flood-related experiences and hail from all across the City of Edina, including the focal geography of the Morningside neighborhood. While their flood-related experiences are diverse, STAFF REPORT Page 2 Task Force members were unanimously concerned for the growing evidence that flooding challenges are worsening and impacting a greater number of Edina residents. The Task Force members have a range of flood-related experiences, and many reside in areas of the City with historically challenging flood conditions. Whether it manifests as inches of water seeping in a resident’s basement, snow melt and rain causing a landlocked basin to creep into a backyard, or a creek backing up against the foundation of a home, flooding is a threat to lives and property. Task Force members were adamant that any FRRS would need to be flexible enough to function under a variety of flooding conditions due to the variety of flooding issues present in the City while still presenting City leadership with a reliable decision-making process and clear recommendations. How we got here The following were identified as primary drivers leading to increased flood risk, listed from most to least impactful: 1. Climate change and changing weather patterns – Climatologists indicate that large, intense rainfall events are occurring more frequently and models predict that large rainfall events will become more intense in the future. This increase is also impacting neighboring communities, is occurring at the watershed level and is expected to get much worse. Add some stats for 2019 weather here. 2. Aging infrastructure and increasing service level expectations – Modeling of storms and risk have improved dramatically in recent decades, which has increased the visual accessibility of flooding information for any community members. The current stormwater system was built for a different time and standard, and service expectations for intensity of land use, drainage, stormwater management, and flood management have increased. 3. Changing development patterns – An increasing trend of imperviousness has spread across the City of Edina. Specifically within the focal geography of Morningside, nearly one million square feet of impervious surfaces (structures, driveways, patios, swimming pool decks, etc.) have been added since 1950. This equates to about 14% of the total size of occupied parcels in the Morningside neighborhood (2019, City of Edina staff). STAFF REPORT Page 3 The work of the Task Force To better understand the nature of the issue, Task Force members requested and were presented with the following:  Overview of the focal geography of Morningside neighborhood, its historical and current flood challenges, and previous efforts to evaluate flood risk reduction options for that geography.  A technical exploration of city-owned stormwater infrastructure, maintenance operations, levels of service, and the stormwater utility.  Regulatory options that have been implemented in other comparable localities and ensuing challenges and trade-offs.  Modeled sensitivity analysis completed by Barr Engineering to explore the potential impact of two potential strategies; comprehensive hard-cover requirements, and enhanced infrastructure including larger pipes and stormwater storage.  Communications strategies that promote preparedness and connect residents with resources during flood events.  Overview of the City’s floodplain management ordinance and other policies that regulate development that can occur within the floodplain to ensure compliance with the National Flood Insurance Program.  A conversation with maintenance staff to understand routine operation and maintenance as well as storm response. Broad categories the City currently operates in.  Infrastructure/utility.  Regulatory controls. Includes floodplain and drainage regulations, permitting and stormwater management standards  Land use.  Emergency response.  Community capacity building. Includes communication, technical support, civic engagement (adopt- a-drain), awareness. The Task Force noted the community perspective on what flooding is and who is responsible varies broadly. Complaints of flooded park spaces have recently been voiced in the community. Many Task Force members have experienced structural damage first-hand and have said a definition for flooding may be helpful. STAFF REPORT Page 4 Key takeaways. Tradeoffs. Opportunities. a. Outline public areas of opportunity (service level definition, preparedness, emergency response, communications, infrastructure) b. Outline private areas of opportunity (preparedness, redevelopment) Some ideas are provided here to start the conversation. This is not an exhaustive list. Infrastructure areas of opportunity Hard cover requirements Barr Engineering provided several deliverables for the Task Force’s review. Models were presented to evaluate the impact on flooding issues in Morningside given two potential solutions: decreased imperviousness and comprehensive stormwater storage. A summary of the results of Barr Engineering’s review of comprehensive hard-cover requirements;  Model presented a sensitivity analysis for different levels of impervious surface reductions across the watershed and the resultant changes for several types of flooding events.  Overall, dramatic reductions in perviousness indicate a modest improvement in flooding issues.  Hard-cover requirements have other valid ecological, water quality, and environmental benefits.  Task Force conclusion: The impact of hard-cover requirements is smaller than anticipated but still an important solution to consider given its other environmental benefits. Stormwater storage A summary of the results of Barr Engineering’s review of enhanced infrastructure including larger pipes and stormwater storage along every parcel in the Morningside neighborhood;  There are about 570 residential parcels in the Morningside neighborhood watershed in Edina.  Cost per cubic foot of underground storage is $10-$20. For 1 inch of runoff, on one 0.25 acre parcel, storage volume is 900 ft3. This equates to about $15,000 +/-$5,000 per parcel per inch of runoff stored. STAFF REPORT Page 5  To capture 2 inches of runoff from every parcel would cost about $5,400,000 (2 inches of runoff is what is generated typically (on the whole) in this area from a 10 year storm event.  For the four lowest structures in the Weber Pond subwatershed, storing 3 inches of runoff on every residential parcel removes the risk for one in the 1% annual chance (100 year).  Task Force conclusion: This solution would provide a moderate benefit for a very high cost. Staff and the Task Force see increasing storage as an opportunity. Coupling storage projects with existing capital expenditures, such as when a road or park is due for reconstruction can result in some efficiencies. The Task Force seemed to favor a more aggressive, ‘built it now’ storage strategy. The Task Force also seem to favor voluntary acquisition as strategy to create space for flood storage. The Task Force and staff seem to agree that maintenance of the existing system was important. The status quo allows for the minimum. All seemed to favor increases in street sweeping, high value infrastructure retrofits, and proactive maintenance. Dredging as a maintenance activity is often performed for a clean water outcome or to keep outfalls open for water flow. Dredging below an outlet does not add storage, unless the water is predictively pumped out of the basin ahead of a storm event. Continued investment in the sanitary sewer system and its resiliency during floods is a key strategy. The city can promote the adopt-a-drain program. Private property owners can volunteer to assist in keeping stormwater infrastructure clear ahead of rain events. Private infrastructure improvements can help to reduce susceptibility to flooding; flood proofing, sump pumps, backflow preventers, resilient landscaping, elevating utilities, etc. Regulatory opportunities Existing controls through the permitting program are intended to result in no new risk. Some Task Force members thought the regulatory controls should do more to reduce risk. Elevation standards reduce risk. When structures are elevated is largely driven by property owners. Barr’s analysis showed an impervious limit would have little impact on flood risk in the Morningside neighborhood. Although an impervious limit supports other values such as open space, room for trees, neighborhood character, and limiting heat island, the case for flood risk reduction was weak. Communications and preparedness opportunities The Task Force expressed a desire for more and better communication. The City could provide increased messaging before, during, and after a flood to include forecasting, preparedness tips, city response, and report on any disruptions. The Task Force also described a desire for more prompt communication in response to requests for service. There seems to be an opportunity to clarify level of service so that callers have a sense for where their issue ranks during a flood response. The city provides sand bags at no cost, including delivery and pick-up. More communication can be done to let people know the service is available. STAFF REPORT Page 6 Private property owners can reduce flood losses by preparing for a flood. FEMA has several resources for flood preparedness; www.floodsmart.gov lists practical before and after tips. Flood insurance through the National Flood Insurance Program is available for anyone who lives in the city to purchase. The city could assist in dispelling the myth that flood insurance is only available in certain circumstances. STAFF REPORT Page 7 City Staff has compiled the following value statements for reaction and discussion. Some statements contradict others, but all represent attempt to summarize Task Force discussions to-date on a variety of proposed solutions and strategies. 1. Resident actions  Edina property owners should fund installation, operation, and maintenance through an increase in stormwater utility fees.  All residents should be educated on the level of service that the City is able to provide, what limitations are, where their stormwater utility fee is being spent, and what their role is.  Residents should take responsibility for all runoff originating on their private property and should be incentivized to collect and manage it onsite.  Neighborhood and community organizations should fill the gap between City services and resident actions. They should also be a primary resource for dissemination of information and for promotion of best practices.  Homeowner strategies and actions that go above and beyond the City’s requirements by homeowners should be incentivized or official recognized. 2. City actions  The street sweeping program should be optimized for a flood risk reduction outcome. Programs such as adopt-a-drain should be promoted to residents to help maintain the drainage service of the stormwater system.  The City should develop a framework to prioritizing capital spending for flood risk reduction projects.  The FRRS should be supported by the City’s creation of a hard-cover policy, such as the one being developed by the Planning Commission.  City should dedicate resources to improving triage and intake during flooding events.  City code related to floodplain development should be strengthened to decrease the amount of development within the floodplain.  Increased funding is needed to support infrastructure improvements that maximize the public opportunities for storage. Funding for ongoing maintenance of improvements is crucial to sustain performance.  Addition of temporary flood storage should be a primary focus of City-led infrastructure improvements.  The city should consider voluntary acquisitions as a flood risk reduction strategy.  Park spaces should be optimized for flood protection and take priority over other uses.  The city should reduce flood water levels in basins only when primary structures are at risk of flooding and the activity will not directly result in flooding of primary structures downstream.  Improvements to reduce flood risk should be prioritized over solving drainage issues. Drainage issues, or nuisance flooding, refers to low levels of inundation that do not pose significant threats to public safety or cause major property damage, but can disrupt routine day-to-day activities, put added strain on infrastructure systems such as roadways and sewers, and cause minor property damage1. STAFF REPORT Page 8  Motivating factors:  Limited space, funding, and public will (in the way of stormwater tradeoffs) means the city cannot solve all flooding and drainage issues. Thus, issues ought to be defined, categorized, and prioritized so that the service level may be defined and communicated.  Flooding and drainage issues vary in the severity of consequences and the ability or willingness for individuals to influence the issue (due to size, scale, and frequency).  Flooding and drainage issues are related. Solving drainage issues can contribute to larger flood problems. 3. Ownership of the issue  The City and local homeowners bear equal responsibility to improve stormwater management.  Public outreach and education around flooding issues will be critical method of ensuring buy-in from residents. This should directly involve underrepresented groups such as renters, low-income, and minority residents.  The City should provide technical assistance to customers facing flooding issues but should also effectively communicate all resident responsibilities. 4. Overall FRRS goals and strategy  Flexibility should be a key element of the FRRS to ensure that all types of flooding in a variety of locations can confidently be addressed by decision-makers.  The FRRS should be prescriptive and regulatory to prevent loopholes and reduce the pressure of enforcement on leadership and staff.  Preventative, proactive measures should be prioritized over reactive strategies.  Falling into the jurisdiction of two watershed districts, flooding in Edina is just a piece of a larger flooding issue. The City should collaborate with other local governments or regional governance structures. Next steps Council work session  October 15th. About an hour available. Materials due by October 8th to submit for the meeting packet.  Staff report and Task Force report separately. CWRMP update Community Engagement around Morningside flood risk, preparedness and infrastructure choices STAFF REPORT Page 9 Attachments Greg Lincoln write up Roxanne Lehmann write up