7 December 2012

Calculating the Cost of Erosion for Coastal Homeowners

Posted by kramsayer

Coastal erosion in Pacifica, Calif, from 1997. (Credit: U.S. Geological Survey)

Erosion takes the “beach” out of beachfront property. And when the sand drifts away, so do the property values.

With climate change predictions that include rising sea levels and more intense storms, the beaches won’t get better. That’s a problem for a lot of people. In the United States, more than half of the population lives near the coast, according to National Oceanic and Atmospheric Administration’s (NOAA’s) study of population trends from 1980-2008.

Although scientists have estimated the effects of erosion on land and ocean ecosystems, those models don’t always help waterfront property owners, said Megan Ware, Boston University undergraduate student, presenting a poster Wednesday morning at the American Geophysical Union’s Fall Meeting in San Francisco.

“I wanted to apply the science in a way that helped people,” Ware said.

She developed a practical way for people to assess their beaches, and then make financial decisions about their properties.

Sand is money, Ware said: the wider the beach, the higher the property value. But when the waterline moves closer, homeowners need to know when it’s worth it to add more sand—a process called beach nourishment—and when it makes more sense to sell.

Imagine a formula similar to one that banks use to figure out whether they’re going to fund a loan. Instead of income, assets, and debts, Ware created a plug-in-the-numbers model that considered factors such as: the slope and length of the shore, the rise in sea level, the volume of sand on the beach, erosion rates, shore length, property value, and beach width. With this information, Ware’s computer model calculates how long sand will stay on the beach to shore up property values and beach house rental incomes.

If it makes financial sense for a homeowner to stay and keep adding sand, Ware’s program can also compare the cost of three scenarios: whether sand should be dumped on the beach just once, added back annually, or supplemented for a specific period of years. In general, the highest net property worth is maintained by adding sand back to the beach every year, Ware said.

Although Ware’s mathematical model was based on erosion data for Plum Island, a beach community off the coast of Massachusetts, it can be adapted to any coastal area by changing the baseline information.

However, it’s also a simple model, accounting only for shoreline changes from rising sea levels. It doesn’t yet factor in sand loss from sediment movement along the coastlines or sudden losses from storm damage, Ware said.

Even though the model isn’t ready to set up on your home computer, it’s the first time anyone has budgeted the cost of sea-level-caused erosion for the homeowner, Ware said.

“It’s also not just for beach property owners. I hope this helps community managers and policymakers, too,” Ware said.

-Elizabeth Devitt is a science communication graduate student at UC Santa Cruz