A thumbnail of a shrimp boat

Constant measurements of ocean currents are important to shipping, commercial fishing, recreational boating, and safety. By using predicted, real-time and short-term forecasted currents, people can safely dock and undock ships, maneuver vessels in confined waterways and safely navigate through coastal waters. With this information, merchandise and people can arrive on schedule. Lack of this knowledge can lead to collisions and delayed arrivals.

Search-and-rescue personnel can use real-time and predicted current patterns to determine where the water may carry a missing person or floating object. Geographic Information Systems (GIS) programs are also used in search-and-rescue efforts. These programs use the last-known position of the lost person or item, predicted and real-time current and weather data, and drift patterns to estimate the location of the person or item.

Coastal Management

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Our nation's coastal zone is vital to the well-being of our country. It is home to roughly half of the nation's population and supports ecologically important habitats and natural resources that are some of our most diverse and well-loved environments. Some of the key elements of coastal management programs include; protecting natural resources, managing development in high hazard areas, giving development priority to coastal-dependent users, providing public access for recreation, and coordinating state and federal actions. Coastal areas, shallow water ports, intracoastal waterways, and estuaries require knowledge of the time and height of the tides as well as the speed and direction of the currents.

Engineers need data to monitor fluctuating tide levels for harbor engineering projects such as the construction of bridges and docks. The construction, demolition, or movement of large structures must be scheduled far in advance if an area experiences wide fluctuations during its tidal cycle. Habitat restoration projects also require accurate knowledge of tide and current conditions.

Emergency Response

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When someone is lost at sea, time is of the essence. Knowing the speed and direction of currents can help the U.S. Coast Guard conduct search and rescue operations with greater accuracy. High frequency radar systems are used to develop maps of surface currents for the Coast Guard to use in their operations. These maps also support other work, such as oil spill response, harmful algal bloom monitoring, and water quality assessments.

In 2010 the British Petroleum (BP) Deep Water Horizon disaster in the Gulf of Mexico released millions of gallons of oil before it was capped. The result from this and other oil spills have far reaching impacts on ecosystems for thousands of cubic kilometers around the spill sites.

View an animation of the Deepwater Horizon oil spill in the Gulf of Mexico.

Hazardous material (HAZMAT) cleanup operations use real-time and predicted tide and current information. Hazardous materials such as oil and fuel from tankers, typically remain on or near the water’s surface, and may be transported by surface currents and winds. Models created from high-frequency radar, satellite, and wind data help predict where the hazardous materials may go.

NOAA’s is working with a prototype quick-response buoy that can be deployed when a HAZMAT spill occurs. The buoy collects real-time current and wind speed and direction, barometric pressure, and water and air temperature. The buoy can be deployed for up to 30 days. Deploying and regular maintenance of data buoys assures scientists, fishers, mariners, rescue personnel and others, of accurate and timely oceanographic and meteorological information.


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Predicting and measuring tides and currents are crucial aspects for vessels to navigate safely in and out of ports, determining the extent of an oil spill, engineering the building of bridges and piers, locating the best fishing spots, preparing for emergencies tracking tsunamis, restoring marshes, and much more.

What's going on in a busy port or the open ocean is much like what's going on at a busy airport and in the skies. Just as aircraft flying need current weather and ground conditions, ships navigating into port and across the ocean need to know exactly what's going on in the water and in the air in real time. This information provides mariners with real-time information such as water levels, current speed and direction, winds, air temperature, and water temperature and salinity. This stream of data is freely available online. Sea going vessels use a system of navigation based on where they want to go as influenced by wind and current - called course,set, and drift. Course is the final destination that a vessel wants to get to but if they initially steer straight for that point the current may force them off course, called drift. So, typically a vessel will set its travel in a direction based on the current and pointing in a direction possibly slight off where they intend to land. The drift of the current will actually place them at their intended destination. Using predicted set and drift to arrive at the destination is the art of adjusting your course and speed to counteract the effect of the current. To cross a river in a boat, you would not point directly across the river at your destination and paddle, but you would point the bow of the boat slightly upstream and use the drift of the current matched against the direction you are pointing to help you arrive where you really want to go.

Moving vessels across oceans and up and down rivers pose special engineering problems for marine architects and engineers. A barge traveling up shallow rivers carrying heavy loads can only draft a few feet or it will be stuck on the river bottom at low tide whereas a container ship carrying thousands of tons of cargo is concerned about storms, currents, and tides on the open ocean and at its docking facilities. In either case, awareness and communication are the key for safe travel for all vessels, large and small.


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The ocean bottom has a rugged bathymetry with an array of natural features including seamounts, canyons, and sand bars. The ocean also contains thousands of artificial hazards such as ship wrecks and unexploded ordinance from previous military campaigns. Survey vessels are designed to survey the ocean bottom to produce detailed charts of the ocean floor that show depths, wrecks, and other subsurface features to facilitate safe navigation.

NOAA vessels use a number of techniques including echo sounding, and side-scan sonar to survey subsurface features. To accurately record sub-surface features on a chart, a number of reference points are used. Before the advent of Global Positioning System which uses a number of satellites whose positions can be measured with extreme accuracy and then referenced to triangulate to the positions on the ground, prominent static positions on Earth's surface were used to determine location at sea. Rock promontories, established light houses, significant underwater features such as sea mounts, and the mean lower-low water were used. Mean lower-low water is an average of the lowest tidal levels for each day over a 19-year epoch. Since MLLW obviously fluctuates, soundings are very conservative and generally greater than recorded.

Using these hydrographic charts the locations of hazards can be determined and recorded for mariners. Often times the position or even size and shape of these hazards may change and once observed, ship captains notify NOAA to update their data.


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Recreation is a fun way to get physical activity and relieve stress, but it’s also big business. Millions of people boat, fish, or just enjoy sitting by a lake, river, or ocean. Entire recreational centers exist just to provide access to and support water based activities. To prevent loss of access to these types of opportunities due to dangerous conditions such as rip currents, toxic algal blooms, pollutants, or severe weather conditions steps are taken to manage water resources through life guards, safety personnel, and science teams. Beach closures for just a single day during peak season can result in extensive economic losses to resort businesses.

Recreational fishers pay close attention to the timing and strength of currents and tides. Knowing when and where tides move bait fish that attract larger fish, or the timing of upwelling coastal currents that bring nutrients where fish may be located, are an enormous benefit. Anadromous fish migrate from salt water to spawn in fresh water in the spring. During migrations of these fish, optimal fishing times correspond to changes in tides, especially tides corresponding to full and new moons. In the open ocean, fishers measure water speed to determine the margin between the stream of faster currents and areas of slow water. It is along these margins that the larger sport fish hunt for bait fish and have the most success.

Dangerous situations often occur during extremes of high and low tide as stranded boaters may try to walk away from their watercraft seeking help and are caught by the incoming rush of high tide. Currents may also steer unaware boaters and swimmers from safe areas. These unsafe conditions can be broadcast through appropriate warning signs and education and close monitoring allows additional safeguards to be put in place for other unpredicted events from weather changes to accidents and spills.

Monitoring water conditions and providing safeguards helps to maintain the safety of everyone wishing to enjoy our nation’s coasts and ocean for recreation.

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