Final Entry

Last Entry

Bangladesh is a target for natural disasters of all sorts including earthquakes, floods, tropical storms, drought, subsidence, and monsoons. However, without contest, those hazards which affect the drinking water supply of this country are the most dangerous. As with many earth-related phenomenon, many of these disasters are linked together as in a chain reaction.  I will review the disastrous effects of tropical storms and drought-related disasters (which include subsidence and other ground water issues).

A word about tropical storms: The tropical storms which Bangladesh is subject to are classified as cyclones (which is just another term for hurricane except that it is more commonly used in the Asian Pacific.) Cyclones/ hurricanes are low pressure systems. At the center on the cyclone spiral is the eye, which has the lowest pressure of the cyclone. Tropical cyclones are warmer low pressure systems which result from passing major thunderstorms. Tropical storms are definitely one of the main foci of the natural disaster mitigation and relief efforts in Bangladesh. The death toll during tropical such the cyclones which hit the coast on a fairly regular basis is usually instantaneous and devastating. As explained in previous entries, some of the most devastating cyclones to affect Bangladesh include the 1970 Bhola Cyclone which killed approximately 500,000 people, and the most recent storm was the Cyclone Sidr which hit Bangladesh in 2007 killed approximately 2,000 people. These storms also cause extreme property damage, wipe out coastal fisheries, cattle populations, deltaic crops, destroy the mangrove forest which protects the western edge of the coast and they contribute to the heavy erosion of the coastal sediment which then contributes to high salinity levels inland. Some years, the coast of Bangladesh is hammered with multiple large-scale cyclones (exp.  In 1983, both in October and November Bangladesh suffered from two separate cyclones).  Approximately 90% of the human loss of life is due to initial storm surge. Storm surge is the sudden wave of water which occurs during a storm such as a hurricane, not to be confused with a tsunami or rogue wave, it is more accurately described as an ocean based flash flood. Surges can travel as far inland as 25 miles and they wipe out nearly everything their path. Bangladesh experiences usually at least on cyclone per year and although the cost of human life has decreased significantly since 1970, the coast never really is allowed the opportunity to fully rebuild its infrastructure or way of life.

However, Bangladesh at least has designed mitigation plans specifically for Cyclones. Mitigation for cyclones includes the construction of cyclone shelters and a coastal warning system which makes it possible for people to leave their homes and either simply move to higher ground, further inland or reach a designated cyclone shelter, or simply the closest shelter to their current area. The coastal areas need to have a strictly regimented cyclone mitigation plan because the coastal population itself is high in number and also ill-organized with a weak infrastructure. The combination of those two components makes cyclones even more dangerous as when they do make land fall the area they strike is filled with people who live in weak structures in close quarters which can cause wide spread panic and miscommunication. The sheer population density, as would be expected hikes up the death toll for those people who remain simply on a statistical basis (the more people left on the coast, the more people killed in the initial storm surge).  Another cause of death is disease and injury as well as loss of livelihood which occur as a direct result of these storms. Furthermore, due to the damage cyclones cause to the sediment of the coast, potable water becomes yet another issue as the delta and the shore erodes salt water seeps into the coast line and moves north with each new surge making the soil barren and the water undrinkable. These cyclones rip up the mangrove forests, contribute to the disintegration of the coast islands (which also protect the central and eastern edges of the coast from storms much like a barrier reef would elsewhere).

The aforementioned brings us to a second major ongoing geological disaster which is water. The issue of water management, preservation and all issues regarding potable water are the most prevalent and dangerous which Bangladesh faces. There are many water-geological problems in Bangladesh; too many to cover in an entry such as this. They are all inter-related and as each new issue comes up there is a sort of domino effect as more and more systems are disturbed. The biggest problem which Bangladesh faces is water availability. In the Northern areas of the country, the ground water is heavily poisoned with arsenic which naturally occurs in the soil. Furth south and especially close to the coast, the ground water and surface water are becoming steadily more and more brackish as the ocean infiltrates the delta, its watershed and seeps into the soil. The aforementioned mangrove forest on the western coast can grow in somewhat brackish water but as the salinity of the soil increases their root systems die. Sea level is also rising (as it all over the world due to climate change). As sea level rises it contributes to the seepage of salt into the coast and it has begun to flood into the delta regions, giving it the same characteristics of a brackish estuary. Also as sea level rises, it erodes the coastal sediment away and the mangroves with weakened root systems do not have any solid ground to cling to so they wash away with the soil. When the mangroves wash away part of the coastal defense against storm surge is weakened which brings us all the way back to the dangers of storm surge in general and not excluding the further salinization of the soil inland.

Because drinkable water is hard to come by in Bangladesh the country has attempted has basically exhausted what little clean ground water by sucking the soil dry. The dryer the soil gets, the more it subsides and. As subsidence worsens, the pores where ground water would normally collect shrink, turning the layers beneath the farmland areas into clay. This makes it hard to grow crops. Clay is not porous enough to become an aquifer again so whenever the monsoons arrive (right around the time the cyclones roll around) instead of some of the rain water seeping back into the earth and replenishing the aquifers for potential extraction later, it all runs off into the ocean again over a weakened and eroded coast line, taking more sediment with it and exacerbating the problem even further.

Obviously, all of the above makes for a fairly constant disaster scenario. Unfortunately, there is very little being done to mitigate the issue. I honestly am not sure what Bangladesh could do to mitigate the water issues it faces short of building a desalinization plant somewhere near the coast. However, such a plant would be in danger of sustaining major damage every time monsoon/tropical storm season came about in the fall. A desalinization plant would also disrupt the local coastal processes, especially the shrimp farming industry as it would suck up anything big enough to fit past its initial grate filter. Bangladesh is fast becoming an inhospitable area especially in regards to water. I predict that as they run out of water options, the people of Bangladesh will be forced to relocate, potentially north or to either one of its neighboring countries, India or Myanmar. Personally I would not build my house anywhere in Bangladesh, but if I had no other choice: I would build my house on high ground to avoid the coastal problems and near the border of India so I could immigrate quickly if necessary. Finally, I would build my house with a large, sturdy rain-water collection system so as to avoid the arsenic in the ground water. I would also have to have a decontamination unit of some kind in order to avoid getting sick via bacteria. Or perhaps I would just have to ignore my personal morals and make a big deal with Pepsi so that I could have crates of bottled water delivered via parachute every week.

https://phulbarinews.wordpress.com/2008/06/24/dewatering-in-open-pit-mining-concern-or-benefit/

http://link.springer.com/chapter/10.1007/978-94-015-8719-8_9

http://www.sciencedirect.com/science/article/pii/S221209631300003X

http://en.wikipedia.org/wiki/Cyclone_Nargis

http://www.royalhaskoningdhv.com/en-gb/projects/cultivating-oysters-to-combat-coastal-erosion-in-bangladesh/107