The Dangers of the Deltas

Deltas are disaster zones in waiting. From the Mekong to the Mississippi, the rich soils and strategic positions of river mouths have long lured farmers, fishers and traders. But the same geography also guarantees they will be periodically inundated.

A case in point was Cyclone Nargis last weekend. As it roared over the sprawling, crowded delta of the Irrawaddy River in Myanmar, the sea surged up to seven miles inland like a slow-motion tsunami, as up to two feet of rain fell. Tens of thousands of people died.

Still, many experts say it is not nature that largely determines the amount of death and destruction in such circumstances, but investment, governance and policy (or the lack of it).

Governments that do not prepare adequately — either through political inertia and underinvestment as in New Orleans, or willful disregard, as critics of the Myanmar junta charge — will continue to see tragic losses.

There is a long list of reasons for countries with low-lying population centers, particularly around rivers, to do more to gird for the worst.

Deltas are evanescent landscapes, formed and occasionally violently rearranged by water. They are implicitly lowlands, built of sediment settling where rivers meet the sea. Most are sinking naturally, as recently deposited silt compresses over time.

In many cases, the subsidence is accelerated by human activities, including the extraction of groundwater and construction of upriver dams, levees and channels, which cut off the renewing flow of silt. In addition, destruction of coastal vegetation leaves exposed soil open to erosion.

Vulnerability will keep rising as populations in poor countries crest in the next few decades, with much of the increase crowding into coastal cities.

Simultaneously, such regions face a faster retreat of coastlines from the rise in sea levels, as climate and oceans warm under the influence of accumulating greenhouse gases, scientists warn.

But human vulnerability can be reduced, as shown in Bangladesh. Though hammered regularly by cyclone-driven floods, it has seen declining death counts since it began investing in warning systems, shelters, coastal housing standards and evacuation plans.

Cyclones in its deltas killed something like half a million people in 1970, and 140,000 in 1991. Last November, aid organizations estimate, the toll from Cyclone Sidr was about 4,000; in that case, more than two million people had taken shelter when the storm struck.

Cyclone Nargis and its aftermath, on the other hand, provide a vivid study in how poverty and insufficient government investment can turn a natural disaster into an outsize human tragedy, said Debarati Guha-Sapir, the director of the World Health Organization’s Collaborating Center for Research on Disaster Epidemiology, in Brussels.

“The villages are in such levels of desperation — housing quality, nutritional status, roads, bridges, dams — that losses were more determined by their condition rather than the force of the cyclone,” she said.

from the NY Times

an interactive map of Nargis' impact on Myanmanr