Towards Representing Pluvial Flooding within a Next Generation Water Modeling Framework

Presentation Overview

This AGU 2025 talk addresses a critical gap in operational flood forecasting: current NOAA NWM/HAND-FIM workflows are designed around fluvial (riverine) flooding but lack explicit representation of pluvial (rainfall-driven surface runoff) inundation. The presentation introduces a spatial index design and validation approach for pluvial flooding that can integrate directly into the NextGen Water Modeling Framework, extending national flood prediction capability to urban and hillslope contexts not currently captured by channel-based models.

The work draws directly on the pluvial flood indices dataset for CONUS — spatially explicit metrics that characterize where and how intensely surface runoff generates flood risk independent of stream channels. These indices are designed to complement, not replace, existing fluvial products.

Why This Matters

• Pluvial flooding accounts for a significant share of flood damage in urban areas but is largely absent from operational national flood warning systems.
• NextGen's modular architecture creates an opening to incorporate pluvial processes — this work develops the spatial representation needed to do that.
• Connecting pluvial indices to an operational framework bridges the gap between research datasets and actionable flood warning products.
• Results inform future FIM software development (FIMserv, FIMbox) as the community expands HAND-FIM beyond riverine channels.