Flooding Committee

Flooding Committee

The Baltimore County Council approved the most recent Ruxton Riderwood Lake Roland Area Improvement Association Community Plan on April 3, 2023. Outreach has begun to key Baltimore County DPW and DEPS staff.

Flooding – Resources 1:

Flood Mapping:
1. Baltimore County uses the one-percent annual chance flood as their definition for flood plain regulation; however, Baltimore County uses a more conservative definition for riverine flood plains than does FEMA. FEMA bases its riverine flood plain limits on runoff calculated on existing land use, presumably to avoid overcharging insurance premiums. Baltimore County bases its riverine flood plains on runoff calculated as if the drainage area were developed to the maximum allowed by zoning. Baltimore County’s reason for using this methodology is to prevent upstream development from putting properties into a flood plain area where one was not mapped previously.
Flood Monitoring and Flood Data:
1. Online interactive mapping application to the Digital Flood Insurance Rate Map (DFIRM), which contains the flood plain data as published by FEMA. This application enables users to select, view and print predefined maps and reports about flood plains in Baltimore County. View instructions (PDF) for using the application.
2. Baltimore County Nuisance Flooding Plan
3. Visual inspection and documentation of streams and rivers within the community before and after severe weather events.
4. Flood Plain Data – Jones Falls Valley
5. Water level and Flow Gauges – Jones Falls Valley
6. Localized weather station data: Lake Roland
7. Localized flooding visual data.
  1. Flooding Photos HERE
  2. Flooding Videos HERE
Environmental Impact Water Quality Monitoring:
Flood Mitigation and Impact Reduction:
1. Flood Impact Studies
2. Flood Impact Restoration Actions:
  1. Jones Falls Valley River Restoration
  2. River Restoration and Flood Prevention
3. Political and Governmental Advocacy:
  1. On a State of Maryland level regarding funding resources for feasible and implementable solutions.
  2. On a Baltimore County level regarding funding resources for feasible and implementable solutions.
Practical Flood Prevention Steps:
1. Reducing the amount of impervious surfaces such as concrete and asphalt paving, as well as buildings. Impervious surface causes water to run off toward a man-made or natural drainage system before the stormwater has an opportunity to percolate into the soil. The runoff also moves faster when there are no plant textures present to slow its progress with this increased velocity causing as much damage as the increase in volume.
2. Reduce the amount of paved parking that is required for new development; consider a maximum parking requirement rather than a minimum one. Shared parking arrangements should be encouraged when adjacent land uses have opposite peak usage times.
3. Require removal of pavement anywhere that old buildings are demolished. If the owners or perpetrators have vanished, the community may be able to receive some assistance with cleaning up a polluted site, or perceived polluted site, which is called a brownfield.
4. Cancel the requirement that residential driveways be paved. If the soil conditions do not lend itself to this solution, driveways with only two paved strips or permeable pavers could be recommended.
5. Investigate permeable pavements for parking lots and other low-usage areas. Permeable versions of both concrete and asphalt are available. Permeable pavement requires some periodic maintenance that amounts to vacuuming out the silt and debris, but it allows stormwater to percolate slowly into the ground.
6. Require riparian buffers (strips of vegetation) alongside rivers and creeks, with the width of the buffer strip proportional to the size of the water body. At least 25 feet is a minimum flood prevention practice, and an ideal buffer is more in the range of 150 feet for a larger urban stream. No paving or building should be allowed within this buffer.
7. Educate the community on the value of plants that are native to the area. Typically, such plants have far longer root systems than plants imported from other geographies. This deeper root system holds soil in place much better and prevents the erosion that can contribute to flash flooding. Not all vegetation is equal in slowing down and absorbing stormwater. Turf grass, mowed to a typical lawn height, has shallow roots compared with the plants that are to your area. Turf grass does not store as much water, and due to its short height, it also does not slow the velocity as much as a taller native planting plan. The value of plant materials in processing stormwater runoff is three-fold:
  1. The plant materials slow the rate (speed) of runoff, which allows streams to “catch up” with the amount of rain or snow melt coming their way.
  2. The plant materials slowing of the flow allows some moisture to percolate into the soil, where plants uptake some water for themselves and let the leftover water seep deeper to that the groundwater recharges.
  3. The plant materials capture some sediment and clean up some pollutants as water passes through. The first two points are major flood prevention steps for smaller streams.
8. Vegetate stream banks to hold them in place and to slow down water as it finds its way through the stream. Again, use native plants rather than plants imported from other ecosystems (exotics).
9. Encourage residents to discharge their downspouts away from their foundations but into rain gardens, which is simply a term for a planting bed that includes only plants that will tolerate being partially submerged for some period of time. Encourage or require commercial buildings and condo complexes to install retention ponds or rain gardens, taking care to require maintenance as well.
10. Permit and encourage the use of grassy swales (or rain gardens) along the sides of streets rather than a curb and gutter system. In conjunction with this flash flood prevention measure, individual homeowners should be encouraged to slow runoff from their roofs, so that stormwater runoff doesn’t immediately course down a driveway, for instance, and pool in the swale.
11. Regularly clean trash and debris from streams to increase their capacity to hold water.
12. Preserve the role that wetlands play in flood water storage. Wetlands are defined by characteristic soils and plants. They may be man-made or natural. While your state may exempt tiny wetland areas from regulation, preserving smaller wetlands assists with flood prevention all the same.

Flooding – Resources 2 – Technical Resources:

Regional Resilience Tool Kit Presentation — EPA recently released its Regional Resilience Toolkit, for addressing regional resilience planning needs to address hazards from natural disasters and is working with a handful of pilot communities: https://www.epa.gov/smartgrowth/regional-resilience-toolkit#2020.

Flood Loss Avoidance Benefits of Green Infrastructure for Stormwater Management — This modeling study estimates the flood loss avoidance benefits from application of small storm retention practices for new development and redevelopment nationwide. Over time, the use of green stormwater infrastructure can save hundreds of millions of dollars in flood losses, while just applying the practices to new development and redevelopment only. If retrofitting were to occur, the avoided losses would be even more significant.

Two Webcasts: Lessons Learned Integrating Water Quality and Nature Based Approaches for Hazard Mitigation Webinar and Building Resilient Communities with Green Infrastructure and Hazard Mitigation Planning Webcast — EPA and FEMA worked with three regions – Ashland OR, Albany NY, and the Commonwealth of MA – to pilot projects that have successfully integrated watershed planning, green infrastructure practices and source water protection into FEMA hazard mitigation plans.

Including Watershed Planning and Green Infrastructure into State Hazard Mitigations Plans — EPA fact sheet on the four main benefits of integrating planning and resources for getting started.

Why Connect with your State Hazard Mitigation Office? — EPA fact sheet on the benefits of, and opportunities for, integrating Watershed Plans with FEMA Hazard Mitigation Plans.

Reducing Damage from Localized Flooding: A Guide for Communities (PDF) — This guide was produced by the Federal Emergency Management Agency to help U.S. cities, towns, villages, and counties reduce damage, disruption, and public and private costs caused by localized flooding within their jurisdictions.

A Flood of Benefits – Using Green Infrastructure to Reduce Flood Risk — This report describes how restoration or conservation of forests, wetlands, rivers, and floodplains can reduce flood risk while supporting an array of other benefits.

Strategically Placing Green Infrastructure: Cost-Effective Land Conservation in the Floodplain — This paper estimates the flood damage and costs that can be avoided by preventing development of floodplain parcels in the East River watershed of Wisconsin’s Lower Fox River Basin. The analysis demonstrates how to use a geographic-information-based model to estimate the benefits of green infrastructure in reducing flood damage, compare the benefits to the costs, and target investments to develop cost-effective nonstructural flood damage mitigation policies.

Rain Garden Reserve (PDF) — This case study from the city of Cuyahoga Falls, Ohio, demonstrates how using a series of rain gardens can mitigate localized flooding. The 24,000-square foot park drains an approximately 3-acre residential area and enhances outdoor recreational opportunities for the community.

Rio Reimagined – Rio Salado Urban Waters Partnership — EPA-supported project to protect, restore and revitalize the Salt and Middle Gila River Watershed by restoring ecosystem functions and balancing revitalization with issues of urban resilience and public safety including flood mitigation.

Design for Resilience in Brattleboro’s Lower Whetstone Brook Corridor — The Town of Brattleboro, Vermont applied for EPA technical assistance to address flooding in the neighborhoods along the stretch of Whetstone Brook that flows through the downtown. The design solutions developed through a public process in 2016 identify options for creating resilient redevelopment and recreational opportunities within flood prone areas of the town while protecting water quality and connecting people with the Whetstone Brook.

Green Street Charrette and Concept Design Report for Huntington, West Virginia — EPA-supported technical assistance for a green street charrette for the Huntington Stormwater Utility in West Virginia. This effort helped the community identify concerns related to stormwater and opportunities for implementing green infrastructure concepts.

Regional Design Assistance in the Mid-Atlantic Webinar — In 2019, EPA worked directly with stakeholder communities including Huntington WV to identify and facilitate policy and planning measures that promote green infrastructure and help address flood management and water quality needs using the Resilient Design Assistance Tool developed by EPA’s Office of Research and Development.

Smart Growth Implementation Assistance for Caño Martín Peña, San Juan, Puerto Rico — This EPA technical assistance project supported the community in developing design options to address stormwater management and flooding problems in tandem with the proposed improvements to the area’s traditional drainage infrastructure system and ecosystem restoration project while also providing parks and plazas, and making the neighborhoods more walkable and bikeable.

Flood Loss Avoidance Benefits of Green Infrastructure for Stormwater Management — This modeling study estimates the flood loss avoidance benefits from application of small storm retention practices for new development and redevelopment nationwide. Twenty HUC8 watersheds were modeled in areas where significant growth is expected between 2020 and 2040, using the FEMA Hazus model and national-scale datasets.

Flooding – Resources 3 – How To:

Localized Flooding: Communities susceptible to localized flooding can use models to learn more about the impact green infrastructure can have on managing the flood risk. Hydrologic and hydraulic (H&H) modeling can help identify green and gray infrastructure practices that will meet flood reduction and water quality goals.

For example, the Capitol Region Watershed District in Ramsey County, Minnesota, developed an H&H model to select a set of green infrastructure practices to address localized flooding and phosphorus loading. Selected practices included:

rain gardens,
underground infiltration trenches,
an underground storage and infiltration system, and
a regional stormwater pond.

All of the practices—except the stormwater pond, which was not completed at the time—reduced runoff volumes by 99–100 percent (PDF). Installing green infrastructure—at an estimated cost of $2 million—was more cost-effective than installing an all-gray infrastructure alternative—at an estimated cost $2.5 million for a new 60-inch diameter storm sewer pipe. See: Arlington Pascal Stormwater Improvement Project Presentation from Saint Paul, Minnesota (PDF) and Arlington Pascal Best Management Practices Performance and Cost-Benefit Analysis Project 2007-2010 (PDF)

Riverine Flooding: Communities susceptible to riverine flooding can more effectively manage their flood risk by combining green infrastructure practices with conserving land in or around the floodplain. Geographic-information-based models can help with the following:

estimate the flood damage benefits of green infrastructure
compare the benefits to the cost of conservation
target investments in conservation towards the most cost-effective areas

When preserving open space throughout a watershed, communities may want to target areas with water-absorbing soils in regions experiencing high growth. For example, the Milwaukee Metropolitan Sewerage District (MMSD) partnered with The Conservation Fund to protect land with those characteristics. As of 2013, the Greenseams program had protected over 2,700 acres of land capable of storing an estimated 1.3 billion gallons of water. Protecting that land reduced future flows and contaminants into receiving rivers, mitigating future flooding.

Flooding – Resources 4 – “Let’s not throw the forest with the stormwater project” By Barbara Southworth:

Tim Wheeler’s article, Stream restoration tactics challenged, (Bay Journal, October) spotlights some of the growing body of published research and citizen resistance faulting the specious application of stormwater management schemes that gut suburban stream habitats in mature forest, reducing them to engineered landscapes with diminished ecological function. Purported to lessen sedimentation and the nitrogen and phosphorus pollution that contribute to water quality decline, MS4 (short for Municipal Separate Storm Sewer System) programs require urbanized localities to gain pollution control credits for managing storm-water discharge. However, as the Bay Journal reported, as “states and localities scramble to meet their obligation for restoring the Bay’s water quality” by achieving regulatory requirements to reduce stormwater pollution, localities often rely on the most ruinous options offered by Dave Rosgen’s so-called Natural Channel Design system.

Engineering small stream courses, such as the Virginia sites featured in the recent article, that never had flood plains to begin with (according to former Hollin Hills resident and internationally recognized fluvial geomorphologist John Field) indicates that localities and the stream restoration industry fail to properly assess, weigh or protect the full range of ecosystem services provided by the old-age forests they destroy in a contrary application of Clean Water regulations.

Such ecosystem services include cooling stream and air temperatures, storing carbon, filtering pollution, recharging groundwater, enhancing property values, managing stormwater and, importantly, supporting natural systems and food webs — not to mention the connections with natural forests that people value and seek out.

Diverse relationships among soil, water, native plants, insects and animals create complexity and stability that is impossible to fully engineer, and they take generational time scales to develop. Alarmed about “stream restoration” projects contrived with scant regard for the biological wealth they squander, citizen groups are fighting to alert the public and save cherished forests. We urge regulators, local officials and the stormwater industry to respect existing forest integrity, rethink stormwater management, and access robust systems biology based on actual site measurements and monitoring, not models using inappropriate and inflated reference values from distant and unlike watersheds.

Actual test results from the Hollin Hills stream sites slated for destruction reveal low to very low phosphorus and nitrogen, according to independent testing, as opposed to surprisingly high figures used by Fairfax County, VA. Will sediment transport (or non-existent pollution) decrease once the small headwater stream valley is laid bare, save for seedlings and saplings of a greatly reduced number of species than currently exists there?

Both parks in Hollin Hills are significantly more diverse and higher quality than what has been represented by Fairfax County. Currently, 87 native plant species are found in Goodman Park and 74 in Brickelmaier Park, documented by ecologist Rod Simmons working independently, that weren’t discovered by Fairfax County. The number of species proposed for planting is far less, only 15% and 25% respectively of the number found in the parks, some do not exist in the parks. Invasive species have been shown to proliferate after such plantings.

The discrepancy between the plant communities found in the Hollin Hills parks and the proposed plant list for re- vegetating the parks cannot be addressed by quantity alone, despite, as reported, the project manager’s claim that “plans call for replanting more trees and shrubs than are being removed.” As Mr. Wheeler’s article indicates, the woodlands’ massive oaks and their plant and animal community live in relationships developed over many decades.

Moreover, trees designated as “saved” trees on county plans will surely suffer root zone damage and later death, despite inadequate mitigation efforts, such as root-pruning up to 50% of the arc around the tree up to the trunk, because their proximity to paving and heavy equipment puts them smack in the danger zone.

Contrary to Fairfax County’s assessment, the parks do, in fact, shelter forest interior dwelling bird species, including migrating warblers and wood thrushes. Further fragmenting remaining forest habitat does these catastrophically declining birds no favors.

Among other significant critiques of drastically altering existing streams is the apparent violation of Clean Water regulations prohibiting changing one type of waterway to a different type, as obviously seems the case when forested stream habitat is converted to stormwater sewer conveyance; its form and function are distinct from the original. To date, the U.S. Army Corps of Engineers has ignored a request to supply information about permitting this variance.

Rosgen’s Natural Channel Design methods are not the only way to think about streams. But for all the controversy they have generated, they do include less invasive options, typically not considered when bulldozers and engineers are the tools of the trade dominating stream management plans. Option 4, Stabilize Channel in Place, includes softer, habitat-sparing bio-engineering methods. Think wood to reinforce the existing channel and much smaller equipment, not requiring engineering a new channel from scratch, nor constructing 12-foot-wide roads to clear and grade land and handle imported soils and 1– to 2-ton boulders. Landscape management practices should not degrade local ecosystems and the co- evolved associations that are their glue, especially in the name of enhancing Chesapeake Bay water quality. More sustainable development, regulatory and lifestyle approaches are needed to solve the problem of stormwater runoff from impervious surfaces in developed areas, not degrading headwater stream habitat for little Bay benefit.

Flooding – Resources 5 – Public/Private Financing to Solve Flooding:

The City of Hampton closed on Virginia’s first Environmental Impact Bond, a creative outcomes-based tool to finance $12 million in nature-based solutions to localized flooding as part of its Resilient Hampton initiative. These bonds allow investors to support innovative projects with measurable and reportable benefits for communities and the environment and ensure the outcomes of the projects are reported back to the investors. The Chesapeake Bay Foundation and Quantified Ventures, an outcomes-based capital firm based in Washington, DC, provided technical services with respect to developing the three projects, designing the outcome metric, impact measurement, and disclosure aspects of the Environmental Impact Bond.

Hampton’s three critical projects are expected to add more than 8.6 million gallons of storage capacity for stormwater that would otherwise contribute to flooding and polluted runoff in the Newmarket Creek watershed, a key environmental, economic, and transportation corridor.

Hampton has experienced increased flooding frequency and severity in recent years. The Newmarket Creek watershed is central to the City’s water management plans. Through this Environmental Impact Bond, the City of Hampton will predict, measure, and report on the stormwater volume storage capacity added by these projects. The gathered data will inform future public investments in resilience projects that seek to improve quality of life, economic viability, and environmental health for Hampton residents, while also disclosing the measured outcomes to the bond’s investors.

“We are thrilled to further our commitment to innovation, transparency, and storm resilience through the issuance of the first Environmental Impact Bond in the Commonwealth of Virginia,” said Hampton Mayor Donnie Tuck. “We appreciate the many members of the community who have provided input on our Newmarket Creek Water Plan and Resilient Hampton initiatives. The residents of Hampton can look forward to improved storm resilience, cleaner water, and better transportation and recreation infrastructure as a result of these important projects.”

Hampton joins a small but growing number of cities using Environmental Impact Bonds to benefit communities, including Washington, DC, and Atlanta. These are a type of municipal bond that require issuers to predict, measure, and report on the environmental or social outcomes generated by the funded projects. Some Environmental Impact Bonds also connect bond buyers’ financial returns directly to the performance of the funded projects, which allows risk-sharing between the issuer and investors. The requirement for impact measurement and disclosure differentiates Environmental Impact Bonds from traditional Green Bonds, which support specific environmental and climate-related projects, but do not require the same level of rigor in outcome prediction, measurement, and disclosure.

As part of this Environmental Impact Bond, the City of Hampton has committed to having a third-party validator provide a post-construction comparison of the actual stormwater storage capacity created against the predicted 8.6 million gallon capacity increase. This bond qualifies as both an Environmental Impact Bond and a Green Bond, under the International Capital Market Association Green Bond Principles.

The City of Hampton was advised by Davenport & Co. on the transaction. Morgan Stanley served as underwriter, with Wells Fargo as co-manager. Kutak Rock served as bond counsel. CBF and Quantified Ventures work with Hampton on the EIB was funded by a generous one-to-one challenge grant to CBF from an anonymous donor that was matched in part by The Kresge Foundation.

“Cities like Hampton are leading the innovation charge by advancing nature-based solutions that make neighborhoods more resilient. We applaud Hampton’s leadership, creativity, and dedication to building a more resilient city in issuing this Environmental Impact Bond,” said Eric Letsinger, CEO of Quantified Ventures. “Their commitment to community equity and involvement is second to none.”

“With the Resilient Hampton initiative, the city is undertaking an incredible effort to both fight localized flooding and do its part to restore the Chesapeake Bay. By using creative EIB financing to meet these goals, it’s blazing a path that cities around the Bay can follow even when budgets are tight,” said Chesapeake Bay Foundation Lands Program Director and Special Counsel Lee Epstein. “These bonds allow the city to pilot cutting-edge solutions based on natural processes that both prevent flooding and keep runoff from polluting waterways.”

The three prototype resiliency projects that will be constructed with the proceeds from this bond are:

Big Bethel Blueway: A green infrastructure project that will store and slow water through the redesign of existing waterways in order to reduce flooding upstream and downstream in Newmarket Creek. The project creates stormwater storage through the expansion of the main drainage channel, the addition of bioretention cells to backyard drainage swales, and the installation of several weirs in the channel. Newly planted vegetation on the channel banks will filter and slow stormwater runoff before it reaches the waterways. Future funding will transform the existing maintenance path into a recreation trail with additional stormwater storage capacity.
North Armistead Avenue Road Raising and Green Infrastructure: This road raising project will eliminate chronic flooding on a major thoroughfare and evacuation route, improving transportation reliability to Joint Base Langley-Eustis and key economic centers. In connection with the road raising, green infrastructure will be installed in the median and on the road shoulders to help slow, store, and redirect stormwater within the space adjacent to the elevated roadway.
Lake Hampton: This project involves the transformation of a detention pond into a purposefully-designed stormwater park with enhanced stormwater storage capacity. The project will raise the height of the dam and weir to greatly increase potential storage volume, as well as install a series of smaller detention basins with wetland plantings to slow, store, and clean runoff from North Armistead Avenue before it enters the lake.

These efforts are among the first projects associated with the Newmarket Creek Water Plan, which the City developed through its Resilient Hampton initiative after nearly two years of public engagement. The projects benefitted from expert consultation by urban designers from the Netherlands (BoschSlabbers), an architecture and environmental design firm based in New Orleans (Waggonner & Ball), engineering design work by national engineering firm (Moffat & Nichol Engineers), partners (including NGOs, universities, regional planning district commission, state and federal agencies), and by the City’s interdepartmental Resilient Hampton team. Rather than look at flooding alone, Hampton’s approach to Newmarket Creek integrates flood risk mitigation, engineering, urban design, environmental restoration, community assets, and economic development.

“We are pleased to have advised the City of Hampton on this forward-thinking public finance transaction,” said David Rose, Senior Vice President and Manager of Public Finance at Davenport & Company LLC, the City’s Municipal Advisor of record. “This first-of-a-kind issue in the Hampton Roads region and Commonwealth shows the City’s commitment to sustainability and resilience, which is becoming more important to the credit markets and the National Credit Rating Agencies.”

“The City’s willingness to undertake innovative resiliency projects and measure and report on the outcomes positions Hampton as a leader in the Green and Sustainability Bond marketplace,” said Cabray Haines, Executive Director at Morgan Stanley. “Its unique EIB offering enabled the City to tap into a rapidly growing buyer base focused on sustainable investing and attracted participation by leading institutions in the space, who applauded the City’s efforts as setting a new standard for Green municipal issues. The strong investor interest in the EIBs helped reduce financing costs to historically favorable levels.”

“The work this team has done to evangelize the use of impact bonds was not an easy process. We applaud all partners involved in helping the city to fight climate-driven urban flooding through solutions that provide reliable, equitable and innovative water services,” said Jalonne L. White-Newsome, Environment senior program officer with The Kresge Foundation who oversees the Climate Resilient and Equitable Water Systems (CREWS) initiative. “The inequities in our nation’s water systems have a disparate impact on low-income communities and communities of color. The importance of this work is intensified due to the prevailing socioeconomic conditions in the affected neighborhoods. Addressing these challenges will help to safeguard the economic future of Hampton and the general well-being of all residents.”

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