Coastal Hazards
Nepal doesn’t have a coast and didn’t deal with erosion too much, so I researched its neighbor, Bangladesh.
Bangladesh beaches used to house many beach morning glory plants which protected from soil erosion, but they are quickly disappearing.
Bangladesh is home to the longest beach on earth - the Cox’s Bazar-Teknaf sea beach in the Bay of Bengal. In the span of 35 years, from 1989-2024, 1085 hectares of land have degraded at a rate of 31 hectares per year & 284 hectares have accreted at a rate of 8 hectares per year. [Accretion: deposition of sediment; opposite of erosion; occurs when there are calm waters because deposition > removal; degradation: erosion] This has been caused by storm surge, cyclones, waves, current, changes in sea level and climate, beach composition, human interaction, and a large range in elevation between high and low tides.
Tropical cyclones cause tidal bores or tidal waves. These occur when the sea level is very high, at the place where a river or estuary empties into the ocean. It occurs here partly due to the large range between high and low tides. They can be violent and dangerous.
Every year, Bangladesh loses 34 square km of land due to coastal erosion, both from the sea and from rivers. However, this is balanced by a gain of 54 square km per year.
The people who live in Char Mitti are near the sea and many have lost their land and been forced to move multiple times due to coastal erosion and flooding.
Bangladesh is hugely involved in the sand wars. They are doing a lot of construction and so the demand for sand is really high. Over 60% of the sand mined from Bangladesh is estimated to be illegally so. This is increasing erosion. Much of this sand comes through rivers from India and Myanmar and there is a ton of it that enters the country each year. In addition to construction, they use it for landfill for deltas, canals, and drains to make more lands. Illegal sand mining is especially prosperous in the Ganges and Meghna River Basins. They instituted a law in 2010 that was supposed to control mining, but it was not effective nor enforced. The Bangladesh Environmental Lawyers Association has filed hundreds of lawsuits, but the people that are convicted can go free with only a small fine. The laws about where quarries can go are not strict. This mining is causing flood plans to sink, damaging ecosystems, river erosion. In 2020, just two rivers claimed over 5,000 acres of land. This has all led to drier riverbeds and sea water coming in which means the rivers are no longer a source of drinkable water for the communities around them.
Mitigation Strategies:
Beach nourishment. However, sand is not limitless. Also, sediments added need to be similar to those that are already part of a beach’s composition.
Geo Bags: protect from coastal flooding and erosion. Aesthetic and natural-looking, cost-effective compared to rock or concrete, can provide a natural habitat. Can be above or below sea level.
Assessment by satellite imaging, remote sensing, geographic information system.
Adding plants, live or dead. Coir logs also support the growth of vegetation and oppose erosion.
Groins & jetties (only for beaches): however, these both can cause added erosion; deposition will occur, but on the other side erosion will occur.
Tree Revetment: slow the flow of river water thereby slowing erosion and trap sediment in their branches so that it deposits into the soil bed
Gabons: a permanent fix; can be placed below water which would slow the flow.
https://beachapedia.org/Accretion
https://education.nationalgeographic.org/resource/tidal-bore/
https://thewaterchannel.tv/thewaterblog/loose-and-gain-coastal-erosion-in-bangladesh/
https://www.sciencedirect.com/science/article/pii/S1385110125000188
https://soilerosion.com/ways-to-control-river-bank-erosion/
https://www.fibertex.com/products/geosynthetics/geocontainers
Hi Madison, your post is really interesting! Thank you for going into such detail. I am particularly interested in the destructive illegal sand mining because I didn’t realize it was such a big problem, but the demand for sand seems to be growing. After easing your post, I did some research about my country, which is Turkey, and has a very long coastline along the Mediterranean, Aegean, Marmara, and Black Seas. It is a very big problem there too. The biggest sand mining zone is the Sakarya river floodplain, where it is estimated that in the past 40 years 130 million tonnes of sand have been mined completely destroying much of the floodplain. Thank you.
ReplyDeleteHello Madison, your post was really informative which I enjoyed. You provided a lot of information about coastal hazards and how they can affect a country. I also was not aware that sand mining was such a massive issue, this was a cool fact that I was not aware of.
ReplyDeleteHi Madison, great job on this! Your research is really thorough and easy to follow. You explained the coastal erosion issues in Bangladesh clearly, and the details about sand mining and mitigation strategies were especially strong. Nice work!
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