SurfZoneView part of Defence Force training exercise

MetOcean Solutions joined the Defence Technology Agency (DTA) in a training exercise in Army Bay, Whangaparoa during May. As part of a larger trial involving the New Zealand Navy and Air Force, DTA were testing a wave buoy and integrating the data into the SurfZoneView beach landing software.

The field phase of Exercise Joint Waka was held at Army Bay and the inner Hauraki Gulf from 14-19 May 2017. It involved New Zealand Army vehicles, amphibious sealift vessel HMNZS CANTERBURY, and Royal New Zealand Air Force NH90 medium utility helicopters. The exercise sought to enhance the New Zealand Defence Force’s ability to deploy offshore to deal with any contingencies including humanitarian crisis, natural disasters and instability within our region.

Figure 1: HMNZS Canterbury

Figure 2: Amphibious vessel used for the landing exercise.

Developed in a collaboration between DTA and MetOcean Solutions, SurfZoneView allows the visualisation of beach landing conditions. Moving people and equipment from sea to land is one of the most complex tasks completed by the New Zealand Defence Force. Such operations are necessary when port facilities are not available, for example when providing natural disaster relief in New Zealand and the Pacific. The safety and success of shore landings are largely dependent on surf zone conditions, and SurfZoneView uses hydrodynamic modelling to provide a rapid and accurate assessment of the waves and currents at any location. Clear, easy-to-use maps of the nearshore conditions are displayed along with tools to assist with operational decision making.

Figure 3: Dr Jamie Halla (left) and Theo Zlatanov (right) from DTA and Dr Rafael Guedes from MetOcean Solutions (centre) getting ready for the trial on the Canterbury ship.

Senior Oceanographer Dr Rafael Guedes was involved with the trial. “It is very hard to assess the beach conditions when you are out at sea. Wave breaking patterns and surf zone currents can change drastically over only a few tens of metres as they are influenced by local bathymetry. By the time a vessel is close enough to the shore to allow operators to judge conditions, it is often already impacted by the waves. SurfZoneView allows operators to visualise the conditions over a stretch of coastline, to help them decide where the best landing place is that day, or sometime in the near future.

Figure 4: It is very hard to assess nearshore conditions from sea.

“The surf zone conditions vary from day to day depending on wind direction, swell characteristics and general circulation. To model the surf zone, the software needs input data describing offshore conditions. These data can either come from forecasts or from real-time measurements such as those from a wave buoy.

Figure 5: Screenshot from MetOceanView showing the forecast site at the location where the New Zealand Defence Force wavebuoy was deployed.

“In this training exercise, we used both. DTA deployed a wave buoy to provide real-time conditions, and we also set up a high resolution forecast site for the location. We can set up a forecast site within an hour, rapidly making available reliable wind, wave and current predictions. The buoy data provides an accurate description of the local conditions, and the forecast allows us to predict how these conditions will change over time.

“During the training exercise, a local storm developed. Waves near the landing site rose to over 1.5 m in just a few hours, with wave periods progressively increasing and directions shifting from north-east to northerly. The development was tracked on SurfZoneView, allowing us to predict conditions around the shore landing site, and how these would change over time as the storm progressed.”

See the example maps of the maximum wave height predicted by SurfZoneView in Figure 7, during the events marked by the black vertical lines in Figure 6. Information from the model is automatically processed to define safety thresholds including whether it is safe to attempt landing on the shore. These thresholds can then form part of the information assessed by operational staff when making a go / no-go decision.

Figure 6: Forecast provided by MetOcean Solutions during the period of the exercise, showing significant wave height  (Hs) and peak wave period  (Tp). Black vertical lines show the events along the development of the storm chosen as input conditions for SurfZoneView. Significant wave height, Hs, is the average height (in metres) of the largest one-third waves. It approximately corresponds to the height of waves as estimated by a trained observer at sea. Peak wave period (Tp) is the wave period (in seconds) of the most energetic waves in a sea state.

Figure 7: As the storm progresses, landing conditions worsen. Example output for the two events highlighted in Figure 6, showing maximum wave height increasing around the landing location. Coloured line along the shoreline displays safety thresholds for the landing vessel. 

“Models are most accurate when we use the best possible input data," adds Rafael. "Wave buoys provide site-specific, accurate data very quickly. Using such buoys alongside SurfZoneView allows the New Zealand Defence Force to go to any location, deploy a buoy and within less than an hour access accurate data to help them land personnel and supplies safely. To aid operation planning, MetOcean Solutions can set up a site-specific forecast for anywhere in the world. This means that we can quickly generate a forecast for wherever SurfZoneView needs to be used, thereby providing the best possible support for the Defence Force and other users.

“We are grateful to be invited to participate in this training exercise. Testing it under real conditions provides important information on where the tool adds value operationally. Coincidentally, we also assisted the Italian Littoral Warfare Unit with similar tests in Sardinia during May, and gained valuable feedback. ”

Figure 8: Based on chart depth, wave height, tide level and wave setup, SurfZoneView displays safe water levels for vessels approaching the shore. Left: map displaying safety thresholds. Right transect (indicated on map) profiles for (top): maximum wave height, including cross-hatched area for breaking waves; and (bottom): water depth and corresponding safety thresholds.

SurfZoneView was developed in close collaboration with DTA, and several overseas navies have indicated interest in purchasing the software.