Flash floods in New Jersey

As New Jersey’s residents face threats from the devastating impacts of extreme rainfall events, which are expected to continue to intensify in their frequency and severity, DEP must continue to protect public safety. The Inland Flood Protection Rule would ensure that areas at most significant risk are better defined and that new and reconstructed assets in these areas are designed and constructed using the best available climate-informed precipitation data. Using the best available data is critical to protecting New Jersey’s assets, economy and, above all, our people from the catastrophic effects of worsening floods.

Purpose

  • To ensure that new investments are well-suited to manage:
    • Current levels of rainfall, runoff and flooding
    • The anticipated future conditions over the lifetime of an asset
  • Support the wise deployment of Ida recovery and water infrastructure investments
  • Inform new development and reconstruction; does not apply to existing development

Key Points

  • New Design Flood Elevation (DFE) raises fluvial (non-tidal) flood elevation mapped by DEP by two feet
  • Requires use of future projected precipitation when calculating flood elevations
  • Ensures that DEP’s Flood Hazard Area permits conform to NJ Uniform Construction Code standards and meet or exceed minimum FEMA National Flood Insurance Program requirements
  • Requires stormwater Best Management Practices (BMPs) to be designed to manage runoff for both today’s storms and future storms
  • Removes use of Rational and Modified Rational methods for stormwater calculations

Addresses Three Issues Related to Increased Precipitation Due to Climate Change

  1. Outdated rainfall data used by DEP rules was computed only through 1999
  2. DEP rules do not account for future increases in precipitation due to climate change
  3. Designs based on current flood mapping are not protective for current and future conditions:
    • Flood mapping reflects prior flooding patterns
    • Does not reflect changes due to climate change