The Irrawaddy River Delta, which is right on the edge of the Continental Shelf, is an area where really big storms can brew. In fact, the Bay of Bengal has the highest density of tropical severe cyclones of anywhere in the world. There are a number conditions that are conducive to developing cyclones and they all fall into place here.
When you combine that with the removal of the mangroves which once fringed the shoreline, you further expose the entire Burmese coast to very substantial increased risk of storm surges.
Clearing the mangroves has certain knowable effects. The mangroves generate a drag on the wind, and if they have been removed over a significant area, it allows for higher wind speeds. It also gives the wind better access to the water so that there is a better transfer of momentum into the water, which means the water travels faster, which in turn helps push it further over the land.
The mangroves also cause a drag on the water. By removing the mangroves you are in effect removing something which decreases the storm surge over land, often the most damaging part of the storm. Then the subsequent rainfall floods the river catchment, which compounds the flooding the storm surge has produced.
But you are not only putting the human environment at risk. There is a risk of increased salt penetration. The Irrawaddy Delta is Burma’s primary rice producing area coming up to a time when the rice crop is harvested. Now it’s gone and the land it grows on has been drenched in salt water, the next rice crop will be affected. It is quite plausible that we will see very substantial humanitarian problems associated with that loss of a food crop at a time when the price of rice is already going through the roof. People could be dying from this event in a year’s time.
Of course, there is a cost/benefit decision made here, and with millions of people to feed, maybe the calculation is that rice farming is the best use of that land. But you have to ask, do you need to farm rice all the way down to the coast? One kilometer of mangroves may in fact be more valuable as a bulwark against damaging cyclones.
But mangroves will only decrease the storm surge penetration. It won’t stop it. Apparently,the Burmese government was urged to get a warning out 24 hours before the storm hit the coast, but they didn’t want to create a public panic. I have a picture here of the warning for the storm on the day the storm hit from one of the newspapers there and it’s on page 15. In most countries affected by tropical cyclones, it would have been on the front pages, and on every television and radio station. The police/military would be mobilised to evacuate the coastal regions.
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The biggest problem is that rivers in countries like Burma are a source of life. River deltas are generally low-lying flat areas which are very open, and very easy for the storm surge to penetrate inland. Areas like these in poorer countries where people have a tendency to live are the exact areas which are most exposed to this type of risk.