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October 2021

Flooding and the Village of Mamaroneck
Part II
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Thanks  to our many readers who viewed Part I of this series. We appreciate your comments. With Part II, the Mamaroneck Project hopes to spark further conversation and provide additional original source documents and facts.

We start this article with deep sympathy for the  family of the individual who lost his life on Mamaroneck Avenue during tropical storm Ida. Here is a link to the GoFundMe page

that was set up to raise funds for his funeral expenses (link now expired). 

It is clear that action must begin immediately to mitigate flooding as many lives are at risk… the lives of residents who live in the flood plain, individuals who depend on roads in the flood plain to travel home, those in the Village needing an ambulance or fire truck that can’t get through streets closed by flooding and first responders who put their own safety at risk to help all of us

The Army Corps Plan – What It Will and Will Not Do

 

Some local officials have promoted the idea that anything short of absolute, unreserved support for the Army Corps of Engineers’ 2017 plan is the same as not caring about flood victims. It appears they are doing so in an attempt to silence public discussion of the specifics of the plan,  in contradiction to democratic principles of discourse regarding public policies.

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Cover of Army Corp July 2017 report.PNG
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Example of channeling a river

The Village administration should review the plan in light of advancing climate change in order to consider if it is sufficient or in need of revision, as well as to consider potential  alternative methods to improve flood mitigation.

 

The Mamaroneck Project believes that facts matter and should be discussed. View the complete Army Corps 2017 Report describing the plan here, and answers the Army Corps provided to residents’ questions in 2016 here

Below are factual details about the plan presented by the Army Corps in 2017.

The plan described in the Army Corps 2017 Report only addresses floods caused by the Mamaroneck and Sheldrake Rivers. The Army Corps Report clearly states that the plan is not designed to mitigate groundwater flooding. [USACE 2016 Responses, p. 1].

 

The plan calls for channeling portions of the Mamaroneck and Sheldrake rivers. Some sections would be widened and deepened, and concrete retaining walls installed. To implement the channelization, the 2017 Report estimates that permanent easements for 14.3 acres of land from 73 lots - of which 53 are privately owned - would need to be acquired for the project. Landowners would be paid for use of their property based on a negotiated amount, with the cost of legal representation in negotiations borne by individual property owners. [USACE 2017 Report 9.3] The Village would acquire use of land by eminent domain if necessary.

In addition to river channelization, the plan calls for an overflow diversion culvert to be built under the Metro North commuter parking lot. The culvert would start just downstream of the Jefferson Avenue Bridge and discharge into the Railroad Bridge opening. [USACE 2017 Report 7.3].

The plan’s projected flood-level reduction varies across the Village. The 2017 Report estimates flooding would be reduced by 2.8  to 4.6 feet – measured from the first floor of structures -  in sections of the floodplain during ‘100-year’ flood levels, such as those in 2007 and Tropical Storm Ida (see illustration from USACE 2017 Report below). Note that this flood reduction is measured from the first floor and does not take into account flooding below first floors – basements, and streets to some degree, are still predicted to flood.

Army Corp flood reduction estimates.PNG
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The 2017 “recommended plan is not designed to reduce river levels in the Harbor Heights area” However, some homes in the area would be selected to be elevated. [USACE 2017 Report 7.7] and [USACE 2016 Responses pp 14 & 16.]

Before greenlighting funds for the Village’s Army Corps Plan, Congress must review and compare its cost-to-benefit ratio. The total projected cost of the plan was updated to $88 million for FYI 2021 with the Village, NYS and Westchester County responsible for paying 35% or roughly $31 million (cash and in-kind service). 

The Village would be responsible for the investigation, testing and clean up of all hazardous substances on any land utilized in the project. [USACE 2017 Report 10-1 (k & l)] 

Sealettro Superfund Report.PNG

Concerns have been raised regarding the impact of the debris, dirt, oil and other contaminants that would be swept into Mamaroneck Harbor as a result of the increased velocity of the water flow caused by the channelization of the rivers. [USACE 2016 Responses pp. 7 &. 8] Any required dredging of the harbor would be at the expense of the Village. [USACE 2017 Report 8.1.1] 

A portion of the proposed project is adjacent to the ITT Sealectro Superfund Site . The 2017 plan describes how the Army Corps intends to handle this section of riverbank.  “Along this portion of the Sheldrake River, a steel-sheet pile retaining wall transitioning to a concrete retaining wall will be built in the channel waterside of the existing retaining wall… If project plans change…to require removal of portion of the streambank within the affected property, the District will coordinate with the NYSDEC to determine how the project will proceed in that area.” [USACE 2017 Report 8.3.2]  

Once completed, the cost of the plan's infrastructure’s annual maintenance will be the responsibility of the project’s nonfederal sponsors. It is unclear what that cost will be to Village taxpayers [USACE 2016 Responses p 31.]

Status of the Army Corps Plan

An important aspect of the Army Corps’ 2017 plan is that it is far from  ‘shovel ready’.

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The 2017 Report states that the plan is “… designed to provide economic justification of the project for determination of federal funding and decisions within the USACE planning process. As the project moves into the design phase more details will be finalized and communicated.” [USACE 2016 Responses p 29.]  Among the surveys and determinations slated for the design phase are –

  • The determination of what land is required for the project. “As part of the design phase, the list of [Lands, Easements, Rights-of-way, Relocations, and Disposals] will be finalized by the USACE and the non-federal sponsor." [USACE 2016 Responses p 11.] The Army Corps. will only be able to confirm the “…details regarding the location of all permanent and temporary easements… once the surveys of the river are completed and project details are plotted.”[USACE 2016 Responses p 11.] 

  • Homes in Harbor Heights. The “USACE identified eight (8) individual structures that would be economically justified to elevate. As stated in the report and communicated to our non-federal sponsors, during the design phase it will be determined the exact number and location of the structures to be elevated." [USACE 2016 Responses p 16.]  

  • Survey of sewer and water pipelines. The USACE 2017 Report states "...the existing sanitary sewer and water pipelines that will be required to be relocated are still being evaluated to determine who owns these lines and whether the owners have a compensable property interest."  "All surveys will be conducted during the design phase (after study approval), including the real estate interest for utilities." [USACE 2016 Responses p. 5] and  [USACE 2017 Report 10-3]  

 

Following completion of the federal approval process and the design phase of the project, the 2017 Report estimates construction would take 33 months. [USACE 2016 Responses p 11.] 

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Army Corps Moving to Nature-Based Flood Mitigation

In 2020, Congress directed the Army Corps to consider nature-based systems on an equal footing with more traditional concrete and steel infrastructure options. This initiative seeks to identify “natural flood control solutions as climate change brings increasingly frequent and severe weather events that test the limits of concrete and steel” (AP Report 10/5/21).  On September 16, the USACE  released this publication: 'International Guidelines on Natural and Nature-Based Features for Flood Risk Management'.

In light of these developments, are there changes the Army Corps could make to the 2017 plan for the Village to make it more nature-based and less reliant on concrete walls along our riverbanks?

Find out more, Nature and Nature-based Flood Mitigation >.

Besides pushing for the Army Corps Plan, what are officials doing right now to mitigate flooding in the Village?

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715 Mamaroneck Avenue
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572 Van Ranst Place
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Review of Village Zoning Regulations in the Floodplain

It appears that the Village Mayor and Trustees have yet to call for a review of Village zoning regulations in the floodplain to determine what revisions make sense with the advance of climate change and increased risk of flooding.

Currently, developers are seeking approvals for two new multi-residential projects in the Washingtonville area  - 715 Mamaroneck Avenue (21 units) and 572 Van Ranst Place (10 units). 

The Army Corps 2017 Report stated “It is true that if new development that is not in accordance with FEMA floodplain regulations and the Village’s floodplain management plan, may increase the risk of flooding… terms of the Local Cooperation Agreement included in the Report require the Village to adhere to an approved USACE Floodplain Management Plan” to maintain eligibility with the program [USACE 2016 Responses p 28.]  

When the Village does not follow FEMA flood prevention guidelines, Village homeowners are at risk of not being able to  purchase flood insurance through the National Flood Insurance program.

Questions:

  • Is the Village following a FEMA approved Floodplain Management Plan?

  • Every community that participates in the National Flood Insurance Program must have a floodplain administrator who works with FEMA. Who is the Flood Administrator for the Village – do we have one?  

  • Does it make sense to increase the density of residential properties in this flood prone area? What would be the risk to residents, and how many more emergency rescues would we ask our valiant first responders to perform in the future with additional multi-residential structures in the floodplain?  

Here is a link to Westchester County's Flooding and Land Use Guide. This manual was created for elected officials, planning and zoning board members, planners and development professionals to improve land use decisions with respect to flooding and flood damage

Obstructions in the Floodway

As we explained in Part I of this series, a ‘floodway’ is the portion of land that lies within a floodplain that serves as the natural conduit for flood waters. Floodways should remain open, free of obstructions, to allow waters to pass through it rather than build up and flood larger areas around it – find out more in FEMA's Guidance for Flood Risk Analysis and Mapping  In the Village, the floodway runs directly through Columbus Park. In the FEMA map below the area marked in blue with orange horizontal bars is the floodway.

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Map produced by FEMA Flood Mapping Service

During  Tropical Storm Ida, a storage container that had been put in the floodway next to the Food Pantry tent in the park was swept up in flood waters. It ended up jammed against the Plaza Avenue Bridge, blocking water from moving under the bridge and down into the Harbor. (See Part I of this article on this site).

Recently, the Village administration permitted storage containers and propane tanks to be re-located directly in the floodway of Columbus Park in disregard of  the flooding risk they present.

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Repositioned storage containers in Columbus Park
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Propane tanks currently in Columbus Park
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Container being removed from river  following Ida floods

We applaud the efforts of the Food Pantry to feed people, but is increasing flood risk the correct solution for this program? Why doesn't the Village come up with an alternative plan to assist this effort?

Provide New Options for Safe, Affordable Housing in  Additional Residential Districts

The Village Trustees and Mayor need to identify new options for providing safe, affordable housing in residential districts that are not prone to severe flooding. For example, The Board of Trustees should review current restrictions on multi-family homes in districts where they are currently prohibited and regulate against  basement dwelling units within the floodplain in order to save lives.

Flood Mitigation Committee

 

The Village's Flood Mitigation Advisory Committee is hard at work studying numerous topics in the aftermath of Ida. These include a review of some aspects of the Army Corps 2017 plan and Village emergency procedures before and during a flood event. Here is a link to the Committee's recent recommendations to the Board of Trustees. More information about the Committee and a link to send a communication to them can be found here.

The Mamaroneck Project Point of View
Glasses

The Mamaroneck Project Viewpoint

Climate change has brought enormous challenges to all municipalities, and  it’s impossible to prevent significant flooding in the Village. The Village must  plan better now – regardless of the status of the Army Corps Plan.

As reported in the NY Times, new data shows that flood risk across the US is far greater than government estimates show.

 

Zoning changes should be enacted as soon as possible for more sensible development in the flood plain, to make housing as safe as possible for residents, and to  align with all FEMA requirements and regulations.

The Army Corps plan should be re-evaluated in light of the new guidelines published for nature-based flood control.