Resilience Scanner

Building-Scale Hydrodynamic Flood Modeling with Sea Level Rise Scenarios

Solution Overview

New York City employs advanced building-scale hydrodynamic modeling to simulate coastal flooding induced by historical hurricanes under various 21st-century sea level rise scenarios.[2] This approach utilizes computational models that account for nonlinear interactions between rising seas and urban flood dynamics, revealing how floodwater depths and velocities change in ways that cannot be predicted through simple linear addition of sea level rise to baseline flood conditions.[2] The modeling framework further implements human vulnerability assessments to quantify how physical risks to individuals respond to sea level rise effects on flood hazards across the city's built environment.[2]

Technical Components

The building-scale hydrodynamic model conducts numerical experiments to quantify the effects of various sea level rise scenarios on flood hazards throughout New York City's urban landscape.[2] Model simulations demonstrate that floodwater depth under a sea level rise scenario can substantially differ from depths estimated through linear addition of sea level rise to control-run floodwater depths, due to complex nonlinear interactions within the urban environment.[2] The modeling framework incorporates projections relative to the Mean Higher High Water tidal datum at The Battery, NYC, based on the 1983-2001 tidal epoch.[3] Under the RCP8.5 greenhouse gas concentration trajectory, the median projection of 2100 relative sea level around New York City reaches 0.96 m, with the likely range extending from 0.7 to 1.3 m by century's end.[2]

Implementation Details

The New York City Panel on Climate Change, a special advisory group of academic and private-sector experts, provides the city with up-to-date science information on future climate change-related risks and adaptation recommendations.[1] New York City actively employs earlier NPCC results from 2015 as the current scientific basis for the city's ongoing and planned coastal resiliency programs.[1] City officials are working with the New York City Panel on Climate Change to develop a new set of coastal protection standards for all new and substantially improved infrastructure in the floodplain, based on the latest climate science to ensure critical infrastructure protection against future flood risks.[4] For planning purposes, the City uses the NPCC's high-end projections for the 2020s and 2050s to ensure preparation for the full range of possible climate futures and that investments made today will protect the city for decades to come.[4]

Benefits and Impacts

The hydrodynamic modeling reveals dramatic increases in flood hazard intensity under sea level rise scenarios. Under a 1.04 m sea level rise scenario, the increase in maximum floodwater speed exceeds 2.7 m/s—representing a 1271% increase—in 5% of the area that was flooded under the no-sea level rise control run scenario.[2] The modeling approach enables quantification of how physical vulnerability of individuals to flooding responds to sea level rise effects on flood hazards, providing critical data for emergency planning and infrastructure protection decisions.[2] By revealing nonlinear flood dynamics that differ substantially from simple linear projections, the modeling provides more accurate hazard assessments for coastal protection planning.[2]

Climate Adaptation Relevance

The enhanced dynamic coastal flood modeling directly addresses New York City's escalating sea level rise and coastal flooding risks. By the 2030s, the 1-year coastal flood is projected to reach 2.5 feet above Mean Higher High Water at The Battery—slightly higher than the 99th percentile of observed monthly high tide floods during the 2000-2020 period of 2.3 feet.[3] Projections indicate the 1-year coastal flood will reach 3.3 feet above MHHW by the 2060s and 5.4 feet by 2100.[3] The NPCC projects sea level could rise by an additional 11 to 24 inches by the 2050s, with a high-end projection of up to 31 inches.[4] Under the Antarctic Rapid Ice Melt upper-end scenario—which incorporates recent ice loss trends, improved ice sheet-ocean-atmosphere modeling, and potential ice sheet destabilization—sea level rise could reach up to 2.1 m by the 2080s and up to 2.9 m by 2100 under high greenhouse gas emissions.[1] By 2100, the 1% annual chance floodplain could cover one-third of the city's total area under ARIM, with around one-fifth of the area potentially flooded during monthly high tides.[1]

Business Analysis

The ARIM scenario depicts an alternative physically credible upper-end, yet very low probability late 21st century sea level rise scenario, which could become more likely over longer time horizons.[1] This modeling approach supports the city's decision to use high-end projections for infrastructure planning, ensuring that investments made today account for the full range of possible climate futures rather than median scenarios alone.[4] The development of new coastal protection standards based on building-scale hydrodynamic modeling provides a scientific foundation for regulatory frameworks governing floodplain development and infrastructure improvements.[4] By quantifying nonlinear flood dynamics and human vulnerability under various sea level rise scenarios, the modeling enables more accurate cost-benefit analyses for coastal protection investments and helps justify expenditures on resilience infrastructure designed to withstand extreme upper-end scenarios.[2]

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