Dam Safety Recommendations for Tropical Storm Isaias

Tropical Storm Isaias Forecast. Source: NOAA

We, at Princeton Hydro, care for the health, safety, and well-being of our clients. We are tracking Tropical Storm Isaias closely as it heads up the East Coast, and the most recent precipitation forecast by NOAA is calling for a significant amount of rainfall in the NJ, PA, MD, NY region. Please be advised that the predicted precipitation could potentially pose a risk to your dam, pond, basin, or other structures.

For our clients who own and/or operate dams, levees, and other flood management structures, please take the following precautions, as adopted from a statement issued today by NJDEP Division of Dam Safety and Flood Engineering (see below), seriously:

  • For high/significant hazard dams, check your Emergency Action Plan to ensure that all contacts for emergency notification and emergency resources (engineers, contractors, supplies, etc.) are up to date.
  • Please refresh yourself regarding the dam owner’s responsibilities in the event of an emergency.
  • Please monitor your dam before, during, and after the storm event and report any concerns to your state Dam Safety office.
  • Prior to the storm, please take precautions to ensure that all spillways are clear of debris and that floating objects (boats, floating docks, etc.) which could block a spillway during high flow events are secured, where possible.
  • If you discover that a potential emergency condition exists at the dam, you should immediately contact your state Dam Safety office and the state emergency hotline. You must also contact your engineer, as well as implement your emergency action plan.
  • If your dam has any known vulnerabilities that you wish to discuss in advance of the storm, we recommend that you first contact your engineer. No modifications should be made to the dam without approval from your state Dam Safety office.

If you are a Princeton Hydro client and we provide inspection services to your dam, please reach President Geoffrey Goll, P.E. directly if you have any issues and/or concerns at 908-237-5660 ext. 103 or ggoll@princetonhydro.com. Even if it is after hours and you are concerned about the condition of your dam during this storm event, please do call Geoff directly. Safety is our priority and will do our best to assist you immediately.


State Dam Safety & Emergency Hotline Phone Numbers:

New Jersey:

  • NJDEP Division of Dam Safety and Flood Engineering: 609-984-0859
  • NJDEP Emergency Hotline 1-877-WARNDEP (1-877-927-6337)

New York:

  • NYSDEC, Division of Water, Bureau of Flood Protection and Dam Safety: 518-402-8185

Pennsylvania:

  • PADEP, Bureau of Waterways Engineering and Wetlands, Division of Dam Safety: 717-787-3411
  • PADEP Emergency Hotline: 1-800-541-2050

Maryland:

  • MDE, Water and Science Administration, Dam Safety Division: 410-537-3538
  • MDE’s Emergency Response Division: (866) 633-4686

Connecticut:

  • CT DEEP, Dam Safety Regulatory Program: 860-424-3706
  • DEEP’s Emergency Response Unit: 866-DEP-SPIL (866-337-7745) or 860-424-3338

***IMPORTANT MESSAGE FROM NJDEP***

DAM SAFETY PRECAUTIONS DURING TROPICAL STORM ISAIAS
POSTED: AUGUST 3,  2020 at 9:30 AM

 

This message is from the NJDEP, Division of Dam Safety & Flood Engineering. Based on weather forecasts, it has been determined that the potential for a significant rainfall event exists in the area of your dam. At this time, we are reminding high/significant hazard dam owners to check your Emergency Action Plan to ensure that all contacts for emergency notification and emergency resources (engineers, contractors, supplies, etc.) are up to date. Please also take a moment to refresh yourself regarding the dam owner’s responsibilities in the event of an emergency.

 

Please monitor your dam before, during, and after the storm event and report any concerns to this office. Prior to the storm, please take precautions to ensure that all spillways are clear of debris and that floating objects (boats, floating docks, etc.) which could block a spillway during high flow events are secured, where possible. If you discover that a potential emergency condition exists at the dam, you should immediately contact this office and our 24-Hour DEP Hotline at 1-877-WARNDEP (1-877-927-6337). You must also contact your engineer, as well as implement your emergency action plan.

 

If your dam has any known vulnerabilities that you wish to discuss in advance of the storm, we recommend that you first contact your engineer. You may also contact our office at the number below. No modifications should be made to the dam without approval from this office.

 

Please also be advised that the Division of Dam Safety and Flood Engineering does NOT recommend or require the lowering of impoundments prior to, during, or immediately following a storm event unless the integrity of the dam is in question. If a dam owner chooses to lower an impoundment for any reason, we encourage them to coordinate with local and county emergency management officials to ensure that any increased flow as a result of the lowering does not create flooding conditions downstream of the dam. The dam owner must also coordinate with the Division of Freshwater Fisheries (908-236-2118). A lake lowering permit (issued by Division of Freshwater Fisheries) is usually required prior to lowering.

 

Division of Dam Safety & Flood Engineering
NJ Department of Environmental Protection
609-984-0859

 

Click here for more information about Tropical Storm Isaias, visit NOAA’s National Hurricane Center and Central Pacific Hurricane Center.

Analyzing Mitigation Strategies for Flood-Prone Philadelphia Community

Photo from Eastwick Friends and Neighbors Coalition

Hydrology is the study of the properties, distribution, and effects of water on the Earth’s surface, in the soil and underlying rocks, and in the atmosphere. The hydrologic cycle includes all of the ways in which water cycles from land to the atmosphere and back. Hydrologists study natural water-related events such as drought, rainfall, stormwater runoff, and floods, as well as how to predict and manage such events. On the application side, hydrology provides basic laws, equations, algorithms, procedures, and modeling of these events.

Hydraulics is the study of the mechanical behavior of water in physical systems. In engineering terms, hydraulics is the analysis of how surface and subsurface waters move from one point to the next, such as calculating the depth of flow in a pipe or open channel. Hydraulic analysis is used to evaluate flow in rivers, streams, stormwater management networks, sewers, and much more.

Combined hydrologic and hydraulic data, tools, and models are used for analyzing the impacts that waterflow – precipitation, stormwater, floods, and severe storms – will have on the existing infrastructure. This information is also used to make future land-use decisions and improvements that will work within the constraints of the hydrologic cycle and won’t exacerbate flooding or cause water quality impairment.

Simply put, hydrologic and hydraulic modeling is an essential component of any effective flood risk management plan.

Putting Hydrologic & Hydraulic Analysis to Work in Philadelphia

Eastwick, a low-lying urbanized neighborhood in Southwest Philadelphia, is located in the Schuylkill River Watershed and is almost completely surrounded by water: The Cobbs and Darby creeks to the west, the Delaware River and wetlands to the south, and the Schuylkill River and Mingo Creek to the east. The community is at continual risk of both riverine and coastal flooding, and faces an uncertain future due to sea level rise and riverine flooding exacerbated by climate change.

Princeton Hydro, along with project partners KeystoneConservation and University of Pennsylvania, conducted an analysis of Eastwick, the flood impacts created by the Lower Darby Creek, and the viability of several potential flood mitigation strategies.

Flood mitigation approaches can be structural and nonstructural. Structural mitigation techniques focus on reconstructing landscapes, including building floodwalls/seawalls and installing floodgates/levees. Nonstructural measures work to reduce damage by removing people and property out of risk areas, including zoning, elevating structures, and conducting property buyouts.

For Eastwick, studying stream dynamics is a key component to determining what type of flood mitigation strategies will yield the most success, as well as identifying the approaches that don’t work for this unique area.

Princeton Hydro Senior Ecologist Christiana Pollack CFM, GISP participated in a workshop for Eastwick residents held by CCRUN and the Lower Darby Creek team. The goal of the workshop was to get the community’s input on the accuracy of the predictive models.Princeton Hydro’s study focused on the key problem areas in Eastwick: the confluence of Darby Creek and Cobbs Creek; a constriction at Hook Road and 84th Street; and the Clearview Landfill, which is part of the Lower Darby Creek Superfund site. Additionally, the study sought to answer questions commonly asked by community members related to flooding conditions, with the main question being: What impact does the landfill have on area flooding?

The built-up landfill is actually much higher than the stream bed, which creates a major disconnection between the floodplain and the stream channel. If the landfill didn’t exist, would the community still be at risk? If we increased the floodplain into the landfill, would that reduce neighborhood flooding?

Princeton Hydro set out to answer these questions by developing riverine flooding models primarily using data from US Army Corps of Engineers (USACE), Federal Emergency Management Agency (FEMA), The National Oceanic and Atmospheric Administration (NOAA), and NOAA’s National Weather Service (NWS). FEMA looks at the impacts of 1% storms that are primarily caused by precipitation events as well as coastal storms and storm surge. NOAA looks at the impacts of hurricanes. And, NOAA’s NWS estimates sea, lake and overland storm surge heights from hurricanes.

This is an example of a 2D model showing where the water is originating, how the water flows through the neighborhood, moves to the lower elevations, and eventually sits.

This is an example of a 2D model showing where the water is originating, how the water flows through the neighborhood, moves to the lower elevations, and eventually sits.

The models used 2D animation to show how the water flows in various scenarios, putting long-held assumptions to the test.

The models looked at several different strategies, including the complete removal of the Clearview Landfill, which many people anticipated would be the silver bullet to the area’s flooding. The modeling revealed, however, that those long-held assumptions were invalid. Although the landfill removal completely alters the flood dynamics, the neighborhood would still flood even if the landfill weren’t there. Additionally, the modeling showed that the landfill is actually acting as a levee for a large portion of the Eastwick community.

This model was developed to illustrate how the removal of the landfill impacts waterflow through the Eastwick community.

This model was developed to illustrate how the removal of the landfill impacts waterflow through the Eastwick community.

Ultimately, the research and modeling helped conclude that for the specific scenarios we studied, altering stream dynamics – a non-structural measure – is not a viable flood mitigation strategy.

The USACE is currently undergoing a study in collaboration with the Philadelphia Water Department to test the feasibility of a levee system (a structural control measure), which would protect the Eastwick community by diverting the flood water. Funding for the study is expected to be approved in the coming year.

Take a Deeper Look at Eastwick Flood Mitigation Efforts

There are many studies highlighting flood mitigation strategies, environmental justice, and climate change vulnerability in Eastwick. Princeton Hydro Senior Project Manager and Senior Ecologist, Christiana Pollack CFM, GISP, presented on the flooding in Eastwick at the Consortium for Climate Risk in the Urban Northeast Seminar held at Drexel University. The seminar also featured presentations from Michael Nairn of the University of Pennsylvania Urban Studies Department, Ashley DiCaro of Interface Studios, and Dr. Philip Orton of Stevens Institute of Technology.

You can watch the full seminar here:

For more information about Princeton Hydro’s flood management services, go here: http://bit.ly/PHfloodplain.