*FREE* Download: Using Flood Models to Mitigate Flood Risk

Back in September, NEIWPCC offered a free research webinar on modeling and flood mitigation recommendations for a forested and urban Hudson River tributary watershed. The webinar looked at the Moodna Creek Watershed and Flood Mitigation Assessment and described how flood models were used to inform recommendations for reducing and mitigating existing and anticipated flood risk. This free webinar was hosted by our Environmental Scientist & GIS Manager, Christiana Pollack, GISP, CFM, and Jessica Jahre, CFM, AICP, a Planner with the New Jersey Department of Environmental Protection.

Pollack and Jahre, authors of the assessment, described how they used flood models to inform recommendations for reducing and mitigating existing/anticipated flood risk in the Moodna Creek Watershed. The flood mitigation assessment was conducted by Princeton Hydro and GreenVest, and funded by NEIWPCC through the New York Department of Environmental Conservation’s Hudson River Estuary Program.

If you missed the webinar, but are still interested in flood mitigation and this study, you can download a PDF of the Powerpoint below. With informative graphics and intriguing photos, this presentation will introduce you to flood mitigation strategies and techniques for many different needs.Princeton Hydro specializes in flood planning, policy, analysis, design and risk mitigation services.  To learn more our floodplain management services, visit: bit.ly/floodmanagement

Two-Part Blog Series: Flood Assessment, Mitigation & Management

In this two part blog series, we showcase our work in the Moodna Creek Watershed in order to explore some of the concepts and methods used to estimate flood risk for existing conditions and the year 2050 and develop a flood management strategy (Part One), and traditional engineering and natural systems solutions used to manage and reduce flood risk (Part Two).

Part One: Flood Assessment & Mitigation Analysis in the Moodna Creek Watershed

The greater Moodna Creek watershed covers 180 square miles of eastern Orange County, NY. The watershed includes 22 municipalities and hundreds of streams before joining the Hudson River. This region has seen tremendous growth in recent years with the expansion of regional transit networks and critical infrastructure.

The Moodna Creek watershed can be split into two sub-basins — the Upper Moodna Creek and the Lower Moodna Creek. In the span of 15 months, Hurricane Irene, Tropical Storm Lee, and Hurricane Sandy each have caused significant flooding throughout the Moodna Creek watershed, damaging public facilities, roadways, and private properties. Both sub-basin communities have noted a concern about increased flood risk as more development occurs.

As global temperatures rise, climate models are predicting more intense rainfall events. And, the flood risk for communities along waterways — like the Moodna Creek watershed — will likely increase as time passes. In order to understand existing and future risk from flood events in this flood-prone area, a flood risk management strategy needed to be developed. The strategy uses a cost-benefit analysis to review the feasibility of each measure and the overall impact in reducing flood risks.

With funds provided from a 2016 grant program sponsored by the New England Interstate Waters Pollution Control Commission (NEIWPCC) and the New York State Department of Environmental Conservation’s (NYCDEC) Hudson River Estuary Program (HEP), Princeton Hydro along with a variety of project partners completed a flood assessment and flood mitigation analysis specific to the Lower Moodna Creek watershed.

Let’s take a closer look at our work with the Lower Moodna Creek watershed, and explore some of the methods used to estimate flood risk and develop a flood management strategy:

Lower Moodna Creek Watershed Flood Assessment & Analysis

The primary Lower Moodna Creek project goals were to assess flood vulnerabilities and propose flood mitigation solutions that consider both traditional engineering strategies and natural systems solution approaches (land preservation, wetland/forest restoration, green infrastructure and green water management). The project team focused on ways to use the natural environment to reduce risk.  Instead of strictly focusing on just Moonda Creek, the team took a holistic approach which included all areas that drain into the river too. These analyses were incorporated into a Flood Assessment Master Plan and Flood Mitigation Plan, which will serve as a road map to reducing flooding issues within the watershed.

Managing Flood Risk

The first step in managing flood risk is to understand what type of exposure the communities face. The Moodna Creek project modeled flooding within the watershed during normal rain events, extreme rain events, and future rain events with two primary goals in mind:

Visual assessment being conducted in flood-prone areas of Moodna Creek Watershed.

  • Assess the facilities, infrastructure, and urban development that are at risk from flooding along the Moodna Creek and its tributaries within the study area.
  • Develop a series of hydrologic and hydraulic models to assess the extent of potential flooding from the 10-year (10%), 100-year (1%),  and 500-year (0.2%) storm recurrence intervals within the study area. The modeling includes flows for these storm events under existing conditions and also hypothetical scenarios with predicted increases in precipitation and population growth.

 

The project team used these models and data to propose and evaluate a series of design measures that help reduce and mitigate existing and anticipated flood risk within the study area. Where possible, the proposed solutions prioritized approaches that protect and/or mirror natural flood protection mechanisms within the watershed such as floodplain re-connection and wetland establishment. In addition to flood protection, the project components also provide water quality protection, aesthetics and recreation, pollutant reduction, and wildlife habitat creation.

Land Use and Zoning

Zoning is a powerful tool that determines a region’s exposure to hazards and risk. Zoning determines which uses are permitted, or encouraged, to be built in moderate and high-risk areas. It also prevents certain uses, such as critical facilities, from being built in those areas. Zoning is also a determinant of a region’s character and identity.

In the Lower Moodna Creek watershed, a large majority (82%) of land is zoned for residential use. However, in the flood-prone areas, there is a higher ratio of areas zoned for non-residential uses (commercial, industrial) than in areas that are zoned for potential future development. Specifically, within the 10-year storm recurrence floodplain, 30% of the land is zoned for industrial use. This is likely because several facilities, such as wastewater treatment plants and mills, require access to the river and were strategically developed to be within immediate proximity of waterfront access. The Lower Moodna zoning analysis demonstrated a general preference within watershed to limit residential use of flood-prone areas. 

Land Preservation

Preserving land allows for natural stormwater management, as well as limits the exposure of development, and minimizes sources of erosion within the watershed. Preserved land also maintains the hydrologic and ecologic function of the land by allowing rainwater to be absorbed or retained where it falls and thus minimizing run-off. If the land within the floodplain is preserved, it will never be developed, and therefore the risk — a calculation of rate exposure and the value of the potential damage — is eliminated.  Therefore, land preservation, both within the floodplains and in upland areas, is the best way to minimize flood damage.

Conserved riparian areas also generate a range of ecosystem services, in addition to the hazard mitigation benefits they provide. Protected forests, grasslands, and wetlands along rivers and streams can improve water quality, provide habitat to many species, and offer a wide range of recreational opportunities. Given the co-benefits that protected lands provide, there is growing interest in floodplain conservation as a flood damage reduction strategy.

Within the mapped Lower Moodna floodplains, our assessment determined that there appears to be a slight priority for preserving land most at-risk for flooding. This is likely a consequence of prioritizing land that is closest to riparian areas and preserving wetland areas, which are the most likely to experience flooding. Within the floodplains for the 10-year storm, approximately 22.7% is preserved. For the 100-year storm, approximately 21.2% of the land is preserved. Within the 500-year storm, this number drops slightly to 20.3%. These numbers are so close in part because the difference between the 10-year, 100-year, and 500-year floodplains are small in many areas of the watershed.

Hydrology and Hydraulics

Hydrology is the scientific study of the waters of the earth, with a particular focus on how rainfall and evaporation affect the flow of water in streams and storm drains. Hydraulics is the engineering analysis of the flow of water in channels, pipelines, and other hydraulic structures. Hydrology and hydraulics analyses are a key part of flood management.

As part of this flood assessment, Princeton Hydro created a series of hydrologic and hydraulic (H&H) models to assess the extent of potential flooding from the 10-year, 100-year, and 500-year storm recurrence intervals within the Lower Moodna. The modeling, which included flows for these storm events under existing conditions and future conditions based on predicted increases in precipitation and population growth, makes it easier to assess what new areas are most impacted in the future.

These are just a few of the assessments we conducted to analyze the ways in which flooding within the watershed may be affected by changes in land use, precipitation, and mitigation efforts. The flood models we developed informed our recommendations and proposed flood mitigation solutions for reducing and mitigating existing and anticipated flood risk.

Stay tuned for Part Two of this blog series in which we will explore flood risk-reduction strategies that include both traditional engineering and natural systems solutions. For more information about Princeton Hydro’s flood management services, go here: http://bit.ly/PHfloodplain.

 

Deal Lake Commission Wins Award For “Lake Management Success”

NALMS President Dr. Frank Browne with Princeton Hydro Co-Founder Dr. Stephen Souza accepting the “Lake Management Success Stories” award on behalf of the Deal Lake Commission.

The Deal Lake Commission’s success in the management and restoration of Deal Lake garners a prestigious award from the North American Lake Management Society

 

The North American Lake Management Society (NALMS) awarded the Deal Lake Commission (DLC) with its “2018 Lake Management Success Stories” award. The award, which was presented at the NALMS 38th International Symposium, is given annually to recognize and honor an individual or group that has made significant lake/reservoir management accomplishments.

The DLC has overseen the management and restoration of Deal Lake and its watershed since 1974. Consisting of appointees from the seven municipalities abutting the lake, the DLC’s mission is to provide leadership, guidance and resources to preserve and restore Deal Lake and its tributaries as a healthy and stable ecosystem. A true challenge in an urban environment.

“It has been both a pleasure and an honor to work with the Deal Lake Commission for the past 35 years,” said Dr. Stephen Souza, Princeton Hydro Co-Founder. “They have shown great resolve to tackle some serious problems affecting the lake and its watershed, serving as a great example for other organizations involved in the restoration of urban lakes.”

Deal Lake is New Jersey’s largest coastal lake, encompassing 162 acres. The lake is surrounded by a 4,400-acre highly urbanized watershed, with the majority of development dating back to the 1960s-1980s. As a result, stormwater management, particularly with respect to water quality and volume management can be especially challenging. The DLC has embraced the numerous challenges, and has worked diligently over the years to correct these issues.

Restored shoreline at the Asbury Park Boat Launch in Deal LakeAt the forefront, the DLC has been managing the primary cause of the lake’s eutrophication: stormwater runoff from the surrounding watershed. In 2014, with funding provided through the NJDEP’s 319(h) program, the DLC implemented a number of demonstration projects, specifically the construction of three bioretention basins, the installation of a large manufactured treatment device, the vegetative stabilization of over 500 feet of heavily eroded sections of the shoreline, and the construction of a rain garden at the Deal Lake boat launch.

Collectively these projects were shown to eliminate localized flooding, decrease floatable loading, and reduce nutrient, sediment and pathogen inputs to the lake. These and other projects implemented by the DLC over the years show that despite Deal Lake being located in a highly urbanized watershed, it is possible to implement cost-effective green infrastructure and stormwater retrofit solutions.

Deal Lake recently won another very competitive 319 (h) program for $735,000 for MTDs, tree boxes, and Green infrastructure improvements to Deal Lake, Sunset Lake and Wesley Lake.

The NALMS award nomination application, which was submitted by Dr. Souza, listed a number of additional achievements of the DLC, including:

  • Educating the community, including school children, to increase awareness and appreciation for the natural environment of the lake;
  • Sponsoring and conducting public engaged spring and fall cleanups, which annually result in the removal of 1,000s of pounds of refuse and debris from the lake;
  • Helping homeowners and public groups recognize and mindfully solve problems related to water quality, siltation, and lake restoration;
  • Serving as the liaison between lakeside communities, County agencies, and the NJDEP;
  • Microbial source tracking investigations with Monmouth University and pathogen source identification work with Clean Ocean Action to decrease E. coli loading;
  • Carp removal, invasive species management, and goose control initiatives;
  • Working with State legislators to implement stricter stormwater controls to reduce pollutant loading, increase storm resiliency, and improve recreational fishing;
  • Participating in the NALMS Secchi Dip In; and
  • Proactively suggesting and supporting community-based, practical ideas to improve the overall environmental quality of the lake and its enjoyment by boaters, anglers, hikers, residents and visitors.

For more information on the Deal Lake Commission, visit DealLake.org.

The successful, long-term improvement of a lake or pond requires a proactive management approach that addresses the beyond simply reacting to weed and algae growth and other symptoms of eutrophication. Our staff can design and implement holistic, ecologically-sound solutions for the most difficult weed and algae challenges. Visit our website to learn more about Princeton Hydro’s lake management services: http://bit.ly/pondlake.

New Green Infrastructure Toolkit for Municipalities

Our partner, New Jersey Future, just launched a brand new, interactive website toolkit to help municipalities across the state incorporate green infrastructure projects into their communities. The New Jersey Green Infrastructure Municipal Toolkit will provide expert information on planning, implementing, and sustaining green infrastructure to manage stormwaterThis toolkit acts as a one-stop resource for community leaders who want to sustainably manage stormwater, reduce localized flooding, and improve water quality.

According to the United States EPA, a significant amount of rivers, lakes, ponds, bays, and estuaries in New Jersey fall into the “Impaired Waters” category, meaning that one or more of their uses are not being met. This reality makes green infrastructure more important than ever in the effort to protect our waterways. When it rains, stormwater creates runoff, which often carries pollution to various types of waterbodies. Green stormwater infrastructure helps to absorb and filter rainwater, reducing the pollution entering our waterways and mitigating flooding in our communities. In urban areas, green infrastructure utilizes natural vegetation to divert stormwater, creating a cost-effective and aesthetically-pleasing way to manage water during rain events.

“We designed this toolkit to bring to light the benefits and importance of investing in green infrastructure at the local level,” said Dr. Stephen Souza, co-founder of Princeton Hydro. “Since the current NJ stormwater rules do not require green infrastructure, we hope to inspire municipal engineers and planning board members to believe in the value through our toolkit. Additionally, we hope it will serve as an educational resource to local officials and decision makers in the Garden State.”

For this project, Princeton Hydro was contracted by Clarke Caton Hintz, an architecture, design, and planning firm, leading this effort on behalf of the nonprofit organization New Jersey Future. Our expert engineers and scientists provided real-world examples integrating green infrastructure into development, in hopes of showing those using the toolkit real world evidence of how green infrastructure can be a part of the daily lexicon of stormwater management. Additionally, Dr. Stephen Souza developed performance standards that municipalities can integrate into stormwater management plans, which are available in the Green Infrastructure Municipal Toolkit.