Coastal wetlands protect against hurricane damage

Coastal wetlands can effectively reduce catastrophic flooding such as that caused by hurricane harvey. This is what U.S. Researchers write in the journal "scientific reports.

For a stretch of land in the east coast state of new jersey, they calculated that so-called salt marshes reduce the annual damage caused by flooding by an average of 16 percent.

In the case of hurricane sandy alone, which hit the eastern seaboard of the u.S. In 2012, wetlands prevented $625 million (523 million euros) in damage. This had reduced the total damage caused by sandy by about one percent. In areas directly behind wetlands, the damage was 11 percent less.

In the gulf of mexico, where harvey is currently making landfall, wetlands are also providing dual protection – by weakening high tides and by soaking up water, researchers told the german press agency. In the areas affected by tropical storm harvey, there are still numerous pre-existing or embedded wetlands, more even than on the east coast or in california. However, they are increasingly threatened by development, pollution, dredging for oil pipelines and rising sea levels.

The team of marine scientists, insurance experts and environmental specialists led by siddharth narayan (university of california, santa cruz) used the latest flood and damage assessment models for the study. In it, they fed in a lot of data on the ownership, number, and coarseness of wetlands on the coast of new york and new jersey.

It turned out that in wetland-protected places, which were less than 1.5 meters above sea level, the losses were even 70 percent lower than without this natural protection. Even small, narrow marching areas already offer effective protection – but the coarser, the more effective they are.

"Our computational models have traditionally focused on man-made crustal protection or architectural solutions," said paul wilson of risk software developer RMS. With the new approach, the effect of natural coastal protection could be quantified for the first time.

Houston in texas is currently particularly hard hit by the harvey floods. Experts complain that extensive, unregulated building around the city leaves far too few natural flats to absorb coarser amounts of water. Between 1992 and 2010, 30 percent of the coastal wetlands in surrounding counties were developed, a texas A&M university report shows.

"When it comes to rebuilding, we should invest in these green resources," said michael beck, co-author of the study. So far, only three percent of the grants for coastal protection have gone to wetlands.

A similar research project recently showed that mangrove forests reduce flood damage in the philippines by one-fourth.