Significant inundation events ravage communities

NOAA and Inundation

What is Inundation?

Inundation is a condition in which water covers normally dry land, primarily caused by severe events along rivers or the coast. There are three primary phenomena which cause significant inundation.

• A tsunami is a series of long waves generated by an abrupt, large scale disturbance of the sea (e.g., from an earthquake or landslide). A tsunami caused by a local event arrives minutes after generation, while a tsunami caused by a distant event arrives hours later; both continue for up to 12 hours.
• Storm surge results from a severe storm such as a hurricane or nor'easter which has strong wind and low pressure that drives water onshore.
• An inland flood occurs when moderate precipitation accumulates over several days, intense precipitation falls over a short period, or a river overflows due to an ice/debris jam or dam/levee failure.

Why is Understanding and Predicting Inundation Important?

The 2004 Sumatran Tsunami and the 2004 and 2005 hurricane seasons illustrated the devastating impacts rare but extreme inundation events can have. Annual inland flooding has a significant impact as well; in most years it causes more damage than any other weather-related event, and an average of 93 people lose their lives to inland floods per year. The most severe consequence of inundation is loss of life; inundation-related deaths make up the largest portion of natural hazard-related deaths in this country. Furthermore, damages to property caused by inundation have significant economic impact. Three-fourths of all presidential disaster declarations are associated with flooding. Inland floods routinely cause more damage annually than any other severe weather event – averaging $6.9 billion for the period 1976-2006.

While the science of inundation is generally understood, NOAA research is focused on minimizing the impacts of inundation by improving forecasts and predictive models, enhancing communication of risks and vulnerability, and providing decision support tools to enable planning for both evacuation and land-use. NOAA strives to more accurately model the phenomena that cause inundation, better predict where it will occur, and systematically map the areas that are vulnerable in order to prevent loss of life and minimize damage to property and ecosystems.

What are Key Research Needs?

Forecasts

• Development of next generation numerical models via improved resolution of model grids and data, expanded dimensionality (e.g., from two to three dimensions), and incorporation of community-based advancements.
• Model validation and benchmarking against observations of critical field data from flooding events.
• Additional physical processes in storm surge models such as tides and surface waves, although forecast improvement is heavily influenced by advancement in storm forecasts for track, intensity, and structure.
• Precipitation quantification (observed and predicted) needed to reduce uncertainty in river forecasting and improve warning lead-times for inland floods.
• Prediction of flood velocities for rescue/recovery operations, spill response, port operations, calculation of forces on structures for evaluating infrastructure damage and defining building codes, and flood mapping for state mitigation plans.

Observations

• Enhanced observation systems with hardened platforms and an integrated spatial reference framework for collecting important datasets such as precipitation, water level, currents, and waves during extreme inundation events.
• Expanded collection of high resolution elevation data, enhancement of the spatial reference system using the Global Positioning System (GPS), and transformation tools for consistent referencing of datums.

Communication and Assessments

• Communication and assessment of inundation risk via probabilistic and ensemble modeling approaches, social science assessments, and socioeconomic analysis.
• Visualizations and maps of flooded areas with spatial distribution of water depth.
• Assessment of impacts of inundation and mitigation strategies on ecosystem function and viability.

Impacts of recent extreme inundation events

What NOAA Research is Enhancing Inundation Mitigation?

• NOAA is working to achieve consistent application of vertical datums across the U.S. coast by developing datum transformation tools.
• NOAA is developing high-resolution coastal digital elevation models (DEMs) to support coastal inundation modeling, and is improving geodetic datum controls for vertical positioning in Alaska, Puerto Rico, and the U.S. Virgin Islands.

Tsunamis

• NOAA has developed a tsunami hazard assessment for the U.S. based on historical tsunami and earthquake data, and is researching additional sources of tsunami and improving socio-economic data to create a more robust assessment.
• NOAA has developed a tsunami forecast system that ingests deep ocean tsunami data into tsunami propagation models that provide boundary conditions for high resolution (up to 10 m grid) inundation models.
• Next generation deep sea tsunami detection systems are being developed to contain the costs of maintaining the existing deep ocean array of 39 buoys.
• Next generation inundation models which compute tsunami current velocities are being studied.

Storm Surge

• NOAA is testing storm surge model developments through a community approach based upon standards, benchmarks, and formats to enhance the research-to-operations pathway. This includes an operational testbed to evaluate models of different resolution, cost, and accuracy.
• NOAA is working to build capacity for coastal disaster resilience with state and local partners by developing data, models, decision support tools, and a community of practice.

Inland Floods

• The Hydrometeorology Testbed is linking research and operations to improve quantitative precipitation estimates and forecasts as well as their coupling to hydrologic models.
• Improved quantitative precipitation estimation includes enhancing application of current Doppler radar systems, integrating advanced dual-polarized and gap-filling radars, improving influences of land on precipitation in numerical models, providing probabilistic rainfall estimates that quantify uncertainty, and improving operational multi-sensor capability.
• Applied research efforts are underway to develop and deploy high-resolution river models that improve accuracy by more precisely accounting for spatial variation in precipitation, elevation, soil type and land use.
• Research on Quantitative Precipitation Forecasting (QPF) is developing extreme precipitation decision support tools, verification products, deterministic and statistics-based numerical models for hourly to weekly time scales, and improved understanding of the meteorology of heavy precipitation.
• New maps are being developed in partnership with the National Flood Insurance Program that will provide the spatial extent and depth of water for minor flooding all the way through the flood of record (largest ever observed).

NOAA Requirements

• National Weather Service authority as the U.S. Government entity responsible for providing flood forecast services is established in accordance with the Weather Service Organic Act of 1890 (15 USC 313) and Inland Flood Forecasting and Warning System Act of 2002 (15 USC 313c).
• NOAA tsunami preparedness activities are mandated by the Tsunami Warning and Education Act of 2006 (P.L. 109-424).
• The Coast and Geodetic Research Act (33 USC §§ 883a-883i) provides the basis for supporting navigation services including monitoring water levels.