New Gauge Will Monitor Sea Level Rise

By: Alan Pollock

Topics: Environment , Waterways

The station in Chatham will also include instruments to measure weather conditions, like these shown at a station in Virginia Key, Fla. NOAA PHOTO

CHATHAM — At some point in the future, Lower Cape residents and policymakers will be engaged in a very difficult debate. With rising sea levels, key roads like Route 28 – and entire neighborhoods – may need to be relocated away from the encroaching waves. And that debate will need to be informed by extremely reliable, detailed data.

To that end, federal officials are planning to install a state-of-the-art tide gauge that will collect accurate information on water levels coupled with meteorological data collected at the same site. In the short term, the new monitoring station will provide better real-time information about tides to help boaters navigate the area, but over the course of years and decades, it will provide a clearer picture of long-term changes in sea levels.

The new monitoring station is a joint project of the National Oceanic and Atmospheric Administration, which compiles, reports and archives climate information, and the National Park Service. The station will replace the existing tide gauge at the Chatham Fish Pier, which provides limited data and is vulnerable to storm damage because of its location on the bulkhead.

“We are currently in the design and planning process and, depending on resources, anticipate upgrading the station next year,” NOAA spokesperson Dianna Parker wrote in an email to The Chronicle. “Since the station is being upgraded to a permanent station, it is being designed and located above historical flood levels at the site to make it more resilient to storms. In addition to water level sensors, the station will have sensors that measure wind speed and direction, air temperature, and barometric pressure.”

Having an accurate barometer located very close to the tide gauge is critical, since the weight of the atmosphere influences water levels at any given location.

“Once the station is rebuilt to meet NOAA's water level measurement standards, it will become a partner station of NOAA's National Water Level Observation Network, a network of 210 continuously operating stations across the country,” Parker wrote. Other NOAA tide gauges are located in Nantucket Harbor and Woods Hole.

As it is with the current tide gauge, all of the data collected from the new monitoring station will be available to the public at www.TidesAndCurrents.NOAA.gov. Local mariners will appreciate the extremely accurate, reliable data the station will generate. In some locations, such data is used to help freighters time their passage under low bridges for maximum safety or to navigate shallow waterways.

The National Park Service is helping pay for the station as part of its effort to monitor long-term sea levels for its Northeast Coastal and Barrier Network Program, which uses high-tech stations to track water levels in the areas between Southern New England and Chesapeake Bay. At various national parks in that area, ranging from the Cape Cod National Seashore south to the Colonial National Historical Park in Virginia, changes in water levels are watched very closely. The parks in the network all have extensive coastlines that include uplands, estuaries, coastal marshes and barrier beaches. Together, they contain about 146,300 acres of critical coastal habitat for birds, turtles and marine mammals. They also provide a natural buffer for populated areas.

Cape Cod National Seashore Geographic Information Specialist Mark Adams said the current network of tide gauges is invaluable and well noted for its quality control. “But NOAA doesn't know specifically the concerns we have about places like Pleasant Bay and Nauset Marsh, where tides are somewhat distorted by the space of the estuary, and the local effects are highly variable,” he said.

The National Seashore's key interest in the long term is monitoring ecological changes related to rising sea levels. When water levels change too quickly, salt marshes can disappear, Adams said.

“If you just look vertically at water levels, salt marshes occupy this extremely narrow range,” he said. Fairly small changes in tidal ranges can essentially drown salt marshes that don't adapt quickly enough. Salt marshes are not only nurseries for sea life – including commercially important species – they also provide upland areas with natural protection from storm surges.

“The big question becomes, where do we put the marsh if the sea level has risen?” Adams said. “Do we move Route 28? Do we move the neighborhoods and roads?”

Determining an answer will mean a broad community dialogue, he noted. “And right now there's no planning for that.” Providing accurate information on water levels will at least provide a science-based foundation for that discussion, Adams said.