Tech Tool for Mapping Urban Flood Risk

The dire need for greater resiliency became apparent this past summer when the National Weather Service issued its first-ever flash flood emergency warning for New York City because of heavy rains from Hurricane Ida. Unlike coastal and riverine flooding, urban flooding is a lesser-recognized-and underestimated-threat. While it can be caused by natural disasters, like Hurricanes Ida or Sandy, urban flooding more frequently occurs when significant rainfall overwhelms local stormwater drainage capacity. Therefore, neighborhoods with crumbling or inadequate infrastructure are more prone to flooding. It also tends to affect those who are less likely to be covered by flood insurance.

One of the lessons learned in the aftermath of 2012's Hurricane Sandy was the need for a holistic approach to resilience. Even businesses with the foresight to protect their properties against natural disasters still took a hit to operations from damage to critical infrastructure and supply chain disruption. The city's long-term strategic plan, OneNYC 2050, has set forth sustainable development goals and initiatives to address such climate-related challenges. It includes empowering property owners, policymakers and local communities to work together to develop place-based programs to improve resilience.

Connecting the Dots uses the city's stormwater flood maps developed earlier this year as part of its stormwater resiliency plans. The goal of the app is to better communicate the risk by making the data more accessible to the public so they can take appropriate action. Property owners located in areas with high risk of urban flooding, for instance, should consider mitigation measures to prevent wet basements and sewer backups when a heavy precipitation event is forecasted.

The web app combines the flood hazard data with information from the New York City Hazard Mitigation actions plan and city development layers. The mitigation actions/projects are color coded by category, such as coastal natural resource protection, infrastructure project, prevention and policy and property protection. A pop-up of each project provides a short description, project timeline leading agencies and other relevant details (see figure 1).