Kaatz, Joel

Mr. Kaatz is a National Technical Manager in Stormwater Resilience and co-lead of the Global Flood Risk and Stormwater Management Community of Practice for Arcadis. As a technical advisor and project manager, he specializes in stormwater resiliency assessments, using hydrologic and hydraulic models to adapt communities to increasing precipitation, both inland and as part of coastal flood protection.

Titles from this speaker

Building A Stormwater Flood Resilience Plan: Mapping to Mitigation

Abstract

Objectives:
Communities are facing increasing stormwater flood risk driven by intensified precipitation, sea level rise, storm surge, urban development, and funding challenges. Many lack the tools and frameworks to develop holistic, effective, and actionable mitigation plans. This presentation will describe how to develop a stormwater flood resilience plan, providing communities with a roadmap to assess this risk and implement optimal, equitable, and actionable flood mitigation solutions.

Status:
The approach has been implemented in various municipalities across the US, customized to the specific needs and conditions in each community. Case studies in New York City, Virginia, and New Jersey will be presented.

Methodology:
The approach begins with the development of a stormwater flood risk map, leveraging hydrologic and hydraulic modeling. We will share guidance on adapting the model-building approach to the data and resources available and considerations on how to effectively share flood risk maps with stakeholders and the public. This is followed by an exposure and risk analysis that integrates the latest climate, modeling, and existing infrastructure data to assess and prioritize vulnerabilities. The presentation will cover how this step can be automated to facilitate efficient updates as new datasets become available. After the risk analysis we will present approaches to prioritize project locations and project types, leveraging additional datasets such as risk quantification, asset and infrastructure criticality, social vulnerability, community input, and economic indicators. We'll share dashboards typically created for this process to facilitate stakeholder engagement and support decision making. Using prioritized project locations, we'll describe the process for refining the model in these areas and developing solution concepts that can be used to develop project scoping and funding information, such as concept designs and cost estimates. Both cost estimates and risk quantification information can be used to develop a benefit-cost analysis (BCA). The BCA may be required for federal funding but also provides a policy and communication tool that helps communicate the need and justification for a given project and ensure strategic, cost-effective use of public funding. We will share additional automated tools that help conduct the BCA and are adaptable to each project based on the needs and data available. Finally, we will present public engagement strategies that have been used to ensure community-focused solutions. This methodology has been proven through multiple case studies, which will highlight key considerations and lessons learned for other municipalities interested in developing a stormwater flood resilience plan.

Findings:
Key findings demonstrate that integrating multi-dimensional data sets-such as H&H modeling results, climate projections, social vulnerability indices, and economic metrics-enables effective prioritization of projects and investments. Case studies from NYC, Virginia, and New Jersey illustrate how stakeholder engagement enhances the translation of data into actionable flood mitigation projects. These examples highlight scalable methods for combining technical methods with practical, equitable implementation strategies.

Significance:
This work provides critical guidance for municipalities and floodplain managers to adopt and implement Stormwater Flood Resilience Plans. By offering tools, methodologies, and real-world case studies, it equips communities to proactively address stormwater flood risks and adapt to evolving climate challenges. The insights shared foster collaboration and inform the development of resilient urban environments, ensuring sustainable and equitable solutions.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

14:00:00

14:15:00

Session time

13:30:00

15:00:00

SessionMapping and Modeling Mayhem: A Downpour of Flood Mitigation Solutions

Session locationMcCormick Place, Chicago, Illinois, USA

TopicClimate Change Adaptation and Resilience

Author(s)

Kaatz, Joel

Author(s)J. Kaatz1

Author affiliation(s)Arcadis, U.S., Inc.1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160157

Volume / Issue

Content sourceWEFTEC

Word count10

Comprehensive Stormwater Management: Combining Flood Mitigation and Water Reuse

Abstract

Objectives: Urban areas located near shorelines and/or tidally influenced riverbanks face a growing climate threat from the combined effects of intensified rainfall and elevated outfall tailwater conditions due to sea level rise and/or storm surge. These tailwater conditions pose a challenge to historic sewer systems designed to drain by gravity. In addition to adapting these systems to mitigate flooding, adaptations should align with the concept of the Circular Water Economy, finding innovative ways to reclaim and recycle resources in our water systems to maximize benefits. Drainage improvements as part of the Seaport — Financial District Climate Resilience Master Plan aimed to achieve these dual goals of flood mitigation and water reuse, providing a tangible and aspirational example of facilitating Circular Water Economy goals for other communities.

Lower Manhattan is at the core of New York City's transportation system, economy, and civic life. Yet by the 2040's, Lower Manhattan's shoreline will experience frequent tidal flooding and will be at risk from more frequent and severe storms, like hurricanes and nor'easters, bringing storm surge and rainfall to this low-lying area. This challenge was coupled with designing a coastal flood barrier system in a densely urban area, requiring an assessment of both on-land and in-water solutions (i.e., extending the shoreline of Lower Manhattan) to implement a comprehensive, sustainable, flood risk reduction strategy.

Status: The Master Plan was completed and released in December 2021 and is shared with the public at: [https://fidiseaportclimate.nyc]. The team is currently advancing the early design and engineering of the master plan, which will be completed in 2025. The presentation will cover the completed master plan and new components incorporated in the ongoing design work.

Methodology: To meet these flood mitigation and sustainability goals, NYC Economic Development Corporation worked with an Arcadis-led consultant team to study climate adaptation strategies. The team first built a 1D-2D hydrologic and hydraulic model of the study area, primarily a combined sewer system. One complexity of the model-build was the necessity to include upstream drainage areas and downstream discharge areas along the interceptor system so that operation of storm surge isolation components could be assessed across neighboring flood protection system projects (Image 1). After developing the model, the team identified the depth and extents of surface flooding that would occur under a variety of existing and future extreme weather events (image 2) assuming coastal flood protection without upgrading the existing sewer system. The team then worked across multiple city agencies and stakeholders to develop level-of-service goals for the master plan under future climate events and conducted an alternative analysis to identify a suite of proposed drainage solutions (image 3) that could meet the level-of-service goals. The alternatives were evaluated for performance (image 4), constructability (image 5), cost, long-term and emergency-use operational requirements (e.g., operating large interceptor gates and/or pump stations during hurricane conditions), sustainability and water quality metrics (image 6), and alignment with other design components of this large, multi-disciplinary project (image 7). This integration with other design disciplines was critical to site drainage improvements within a multi-level, community-serving waterfront that maintains access for residents, park space, and active ferry terminals (image 8).

Findings: To achieve the goals of the master plan, the use of the sewer system during extreme weather events had to be re-imagined relative to its original design. After the evaluation described above, a subset of stormwater management solutions was carried forward for further design. These included an innovative approach to reverse the flow in a large-diameter existing interceptor sewer during extreme weather events, a large emergency-use combined sewage pump station, sewer conveyance improvements, and a green infrastructure corridor along the proposed extended shoreline that includes a water reuse program to offset new water demands. The green infrastructure corridor contains a new, entirely separated sewer system to manage rainfall on the shoreline extension, and not further tax the existing combined sewer system.

Significance: The employed methodology, proposed solutions, and lessons-learned provide an example to address similar issues in urban areas impacted by the combined effects of increasing rainfall and tailwater conditions throughout the United States. The project provides insight into challenges with operating combined sewer systems to meet current level-of-service goals under a future climate. It showed how H&H modeling can be used to assess flood risk and develop an alternative analysis to identify mitigation strategies. Further, it shows how the goals of a Circular Water Economy can be achieved through flood mitigation projects. The presentation will provide a case study example on how to build resilience in sewer systems against climate threats in a dense, urban environment, providing lessons learned and sharing innovations with other communities facing similar challenges. It provides an example for how to upgrade aging sewer systems while promoting a Circular Water Economy.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

09:00:00

09:30:00

Session time

08:30:00

09:30:00

SessionBuilding Resilience and Planning for Climate Change

Session locationMcCormick Place, Chicago, Illinois, USA

TopicClimate Change Adaptation and Resilience

Author(s)

Kaatz, Joel, Taylor, Alexis, Deitz, Roni

Author(s)J. Kaatz1, A. Taylor2, R. Deitz1

Author affiliation(s)Arcadis, U.S., Inc.1, NYC Economic Development Corporation (NYCEDC)2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160055

Volume / Issue

Content sourceWEFTEC

Word count10

Description: Upgrading Historic Sewer Systems to Prevent Flooding from Increasing Rainfall and...

Upgrading Historic Sewer Systems to Prevent Flooding from Increasing Rainfall and Elevated Tailwater Conditions - A NYC Case Study

Abstract

Purpose: Urban areas located near shorelines and/or tidally influenced riverbanks face a growing climate threat from the combined effects of increasing and more frequent rainfall and elevated tailwater conditions due to sea level rise and/or storm surge, restricting gravity-driven sewer performance during periods when capacity is needed the most. These tailwater conditions pose a challenge to historic sewer systems designed to drain by gravity, and this challenge is further exacerbated when rainfall rates exceed sewer design capacities. This presentation will share a case study on how to build resilience in sewer systems against these threats in a dense, urban environment, providing lessons learned to other communities facing similar challenges. Overview of Master Plan: Lower Manhattan is at the core of New York City's transportation system, economy, and civic life. Yet by the 2040's, Lower Manhattan's shoreline will begin to experience frequent tidal flooding from sea level rise, impacting streets, sidewalks, buildings, and critical infrastructure. In addition to tidal flooding, Lower Manhattan is at risk from more frequent and severe storms, like hurricanes and nor'easters, bringing storm surge and rainfall to this low-lying area. This has been exemplified by the devastating effects of Hurricane Sandy in 2012 and the record rainfall and widespread pluvial-driven flooding from Tropical Storm Henri (2021), remnants of Hurricane Ida (2021), and remnants of Tropical Storm Ophelia (2023). To reduce both acute and chronic flood risk to the neighborhood, NYC Economic Development Corporation worked with an Arcadis-led consultant team to study climate adaptation strategies and develop a Climate Resilience Master Plan. A major challenge of the master plan was how to upgrade and adapt the city's aging, gravity-driven, combined sewer system to mitigate the combined effects of rainfall, sea-level-rise, and storm surge-driven flooding in this future climate. To do so, the use of the sewer system during extreme weather events had to be re-imagined relative to its original design. This challenge was coupled with designing a coastal flood barrier system in a densely urban area, requiring an assessment of both on-land and in-water solutions (i.e., extending the shoreline of Lower Manhattan via land reclamation) to implement a comprehensive flood risk reduction strategy. To develop the Climate Resilience Master Plan, the team first built a 1D-2D hydrologic and hydraulic (H&H) model of the study area. One complexity of the model-build was the necessity to include upstream drainage areas and downstream discharge areas along the interceptor system so that operation of storm surge isolation components could be assessed across neighboring coastal flood protection system projects. After developing the model, the team identified the depth and extents of surface flooding that would occur under a variety of existing and future extreme weather events assuming a coastal flood protection barrier was implemented without upgrading the existing sewer system. The team then worked across multiple city agencies and stakeholders to develop level-of-service goals for the master plan under these future climate events and developed an alternative analysis to identify a suite of proposed drainage solutions that could meet the level-of-service goals under future sea level rise, storm surge, and rainfall conditions. The alternatives were evaluated for performance, constructability, cost, long-term and emergency-use operational requirements (e.g., operating large interceptor gates and/or pump stations during hurricane conditions), and alignment with other design components of this large, multi-disciplinary project. After evaluation, a subset of stormwater management solutions was carried forward for further development in the master plan, including an innovative approach to reverse the flow in a large-diameter existing interceptor sewer during extreme weather events, a large emergency-use combined sewage pump station, sewer conveyance improvements, and a green infrastructure corridor along the proposed extended shoreline. These solutions needed to fit within a multi-level, community-serving waterfront that maintains access for residents, park space, and active ferry terminals. Benefits of Presentation: Benefits of the presentation include the lessons-learned for many coastal and riverine communities that will face similar climate challenges in coming years, and sharing the innovative solutions employed here that may be considered on similar projects. The presentation will highlight the challenges of designing and siting new drainage infrastructure in dense, space-limited neighborhoods, and considerations for how to integrate this new infrastructure in an existing, aging sewer system. It will discuss considerations regarding coordination with stakeholders on adjacent, ongoing coastal resilience projects. Finally, it will share lessons learned and recommendations to other communities facing similar challenges. Status of Completion: The Master Plan was completed and released in December 2021 and is shared with the public at: [https://fidiseaportclimate.nyc]. The team is currently advancing the early design and engineering of the master plan, which will be completed in 2025. The presentation will cover the completed master plan and new components incorporated in the ongoing work. Conclusion: The employed methodology, proposed solutions, and lessons-learned provide an example to address similar issues in urban areas impacted by the combined effects of increasing rainfall and coastal or tidal riverine tailwater conditions throughout the United States. The presentation will explain the challenges with operating combined sewer systems to meet current level-of-service goals under a future climate and then describe the H&H modeling approach to assess flood risk and alternative analysis to identify mitigation strategies to build a more resilient Lower Manhattan.

This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.

SpeakerKaatz, Joel

Presentation time

14:00:00

14:30:00

Session time

13:30:00

15:00:00

SessionClimate Change Resilience

Session number08

Session locationConnecticut Convention Center, Hartford, Connecticut

TopicClimate Change Adaptation, Climate Change Mitigation, Coastal Systems, Flooding, Funding, Green Infrastructure, Regionalization, Resiliency