Falk Feddersen researches the implications of sea-level rise on our beaches.
By Mario C. Aguilera / Scripps Institute of Oceanography / May 02, 2014
Falk Feddersen is an acting professor of coastal physical oceanography at Scripps Institution of Oceanography, UC San Diego. His studies on various aspects of coastal and nearshore oceanography—spanning waves, currents, turbulence, and biological processes— have helped further the scientific understanding of how pollution moves across coastlines. His research includes instrument development, observations, theory, modeling, and extensive field work. He received his Ph.D. from Scripps in 1999.
What is your role in researching sea-level rise and its implications?
I study how waves come into the beach, break, and dissipate their energy, as well as how sand moves from the top of the beach all the way out to many hundreds of yards offshore. The processes that I’m studying happen on time scales anywhere from an hour to a couple of months. The time scale for sea-level rise is, of course, much longer than this—on the order of decades to a century. With climate change there is also very likely going to be increased storms and wave activity, which is going to act to reconfigure the beach much more strongly than is happening right now, along with sea-level rise.
How do you use scientific instrumentation in your research?
In our group we have a whole range of instrumentation, a lot of it we’ve developed in-house. We go out, and we put it into the water, some of it right at the beach edge, all the way out to a couple of hundred meters offshore. We measure the waves and currents, take beach profiles, and a range of other things. Then we analyze the data and try to relate how the waves, tides, winds, and other forces affect things like shoreline erosion and a whole range of surfzone processes, including how the beach itself changes.
How does your research relate to sea-level rise?
As waves come in toward shore they move sand around and they change the configuration of the beach. They can erode the beach and in some cases accrete (add sand to) the beach. This relates to sea-level rise because many beaches are set up in a kind of equilibrium state. They like the configuration they are in. But when you have sea-level rise, and when you have increasing storms, that’s going to affect this equilibrium state and lead to a lot of erosion and a lot of change along coastlines. With this type of erosion you could end up with nothing but a sea wall and rocky gravel, and no beach at all. That’s the extreme end but we don’t know exactly how much erosion is going to happen.
What are some of the impacts caused by sea-level rise in the next 50 years? 100 years?
The implications of sea-level rise and why we need to be aware of it is simply because sea-level rise is generally imperceptible to us right now. There is almost no sea-level rise right now in California and the reasons have to do with things that happen on inter-annual and decadal time scales.
So sea-level rise is an avalanche that’s on the horizon. It’s coming, we know it’s coming, and there’s nothing we can do about it because of the amount of carbon dioxide that we’ve already put into the atmosphere, even if we cut emissions today. So it is going to dramatically reconfigure the coastlines. As the sea level goes up—and there’s also very large likelihood that there are going to be more storms, meaning more wave events—the beaches are going to be drastically different in 50 years and for certain in 100 years. Your kids, when they are grandparents taking their grandkids to beautiful La Jolla Shores, for example, the beach may look nothing like this—they may not even recognize it.
As a society, in terms of adaption, we have to start making the decisions about when we are losing a beach: Do we want to just keep on putting new sand on the beach and then have that sand erode? Is the cost of doing that worth it in terms of the pleasure that society is getting from the beach? Or, is it better to say, maybe we need to break down these sea walls, erode further back, and then we can get natural sand again from the cliffs and dunes.
What should the public and especially coastal communities know about sea-level rise and its impacts?
Mission Beach here in San Diego County, for example, is a very dense isthmus of sand and there is a dense residential population and a lot of commercial stuff going on there. That could all disappear in the next 50 to 100 years depending on the rate of sea-level rise and other factors. It’s definitely going to be heavily impacted. The roller coaster that’s there, the businesses, all could be gone in 100 years. Similarly in the North County of San Diego, in parts of Solana Beach and Encinitas, there is a lot of development on top of the cliffs. Those cliffs are already eroding, but with sea-level rise they are very likely to erode much more rapidly and the property on top of the cliffs, the threat for them is going to be greater and increase more rapidly.
So there are very strong economic reasons why this is important. Sea-level rise is not only going to impact the open coast, and so if a place like Mission Beach basically becomes flooded, then all those businesses and the homeowners and the property values there will go to zero and the people will suffer dramatic economic losses which will be on the order of a permanent Hurricane Sandy hitting New York.
The other sorts of impacts are on wetlands and on ecosystems and on all the creatures that inhabit the coastal zones, for example, from the rocky intertidal to all the wetlands and marshes inside estuaries such as down in the Tijuana River estuary.
What role does Scripps have in developing the research needed to more fully understand sea-level rise and its impacts?
Here at Scripps Institution of Oceanography there are a wide range of researchers studying a variety of problems that are related to both sea-level rise and the adaptation to sea-level rise. This spans a great deal of research areas, and an interesting aspect of this is that the continent itself is sinking to a certain degree. So even if sea-level rise doesn’t change, a sinking continent can seem like sea-level rise. There are regional differences. The city of San Diego can be sinking or rising differently than Oceanside, and differently than Huntington Beach, Long Beach, and Los Angeles. Similarly there are people here who study how the storms in the Pacific that generate the waves that erode the beaches, how those are changing with climate change.