Problem

Many low lying areas of Pacific Islands are experiencing marine flooding events that currently strike with little to no warning.  Currently, if and when there is a warning, the warnings are vague at best and do little to inform inhabitants of the severity of the impending event.  There is a very real need throughout the pacific islands for a tool that is able to predict when and how severe marine flooding events will be. Effects include but are not limited to:  loss of life from drowning; loss of and damage to property, crops, infrastructure, etc.  There are also a number of environmental effects from inundation that include but are not limited to:  salt intrusion into the water table, erosion, water quality effects on the reef ecosystem after the water recedes, etc.  Long term effects of inundation can lead to an island being uninhabitable.


Aim of Project

The aim of this project is to provide all nations and people living on a coral reef-lined coast anywhere in the world with forecasts of wave-driven flood events.

The Early Warning System (EWS) will be developed in close consultation with users. There will be a range of options that will be made available to users for the derivation of forecasts and warnings. For those Nations with the capability to derive and disseminate the forecasts and warnings themselves, the project team will work closely with the relevant agencies to provide them with the ability to run the models themselves. For those users who prefer that NOAA or another agency provide a packaged product then we will work with those users to ensure that the package that is developed and run at NOAA is appropriate and fit for purpose.

Regarding the outputs of the forecasts, the development of these are flexible and will be developed in conjunction with users so that they are useful, understandable and fit for purpose. Not all users will want the product developed by NOAA and so it makes sense to assist those users to develop their own outputs and warnings.


WaveFORCE

The Wave-driven Flood-forecast of Reef-lined Coasts Early warning system (WaveFORCE) will provide coastal flood forecasts from the present up to 180 hours into the future at a 3-hour interval, with the forecasts being updated once every 6 hours. This means that every six hours a new set of forecasts will be generated which provide the user with a set of 180 forecasts for each point along the entire coast at 200 metre intervals. The 180 forecasts at each point will cover the time from the present out to approx. 7.5 days at 3 hourly intervals.

Rather than using expensive wave-rider buoys for input data to the model, NOAA have the ability to combine satellite data and hydrodynamic models to derive sea surface height and wave height, period and direction globally. Deltares and USGS have developed a simple model that predicts wave-runup given the input of wave and sea surface height outside the reef. This simple model successfully propagates the waves across the reef, through the lagoon and up onto the land, where the extent of the runup can be predicted.

The sea surface height is a combination of: tides, local sea level (which fluctuates on a daily to weekly time scale), storm surge (from near-by storms or cyclones), short term climate change (e.g. ENSO and PDO), and long term climate change (e.g. due to global warming). Waves can be categorized into locally-derived storm waves that are generated by nearby storms or cyclones (i.e. short wavelength wind waves) and those waves that are generated by distant storms (e.g. long wavelength swell waves from storms in the Arctic and Antarctic or cyclones somewhere else in the ocean basin). Tsunamis are also a source of waves that can cause flooding, however this WaveFORCE will not produce forecasts that include tsunamis, these are covered by other forecasting systems.

The WaveFORCE methodology has been successfully tested at a case study site at Roi-Namur, Kwajalein, RMI. The initial simulations showed that hindcasts of wave run-up using the WaveFORCE methodology and satellite-derived estimates of reef geometry are less accurate by 6-49% than outputs from a more sophisticated high-resolution model called XBeach. However, including an estimate of reef depth (in this case, using local knowledge of MSL of -0.5±0.5m) alongside satellite-derived reef width, increases the skill of the WaveFORCE methodology such that the error relative to the XBeach high resolution model is just 7%. 

 


User Interaction

The entire process will involve users via workshops and user interactions. User input during the development, user instruction during the delivery and user feedback during the entire process will be a key component to the entire project.


Early Warning System Methodology

 

Project Team

 

Name Organisation
Curt Stolazzi USGS, US
William Skirving NOAA, US
Ap van Dongeren Deltares, Netherlands
Robert McCall Deltares, Netherlands 
Ron Hoeke  CSIRO, Australia
Eric Leuliette NOAA, US 
Benjamine Marsh  NOAA, US
Jacqueline De La Cour NOAA, US 
Mark Eakin NOAA, US