Whom to Blame for a 'Manageable' Hazard ? --- Part 1

In past century, the natural hazard in the form of floods has become the most dominant disaster in the Himalayan region in terms of the frequency and scale of the damage that has been done. For examples, in Bangladesh flood of 1998, about 1000 people perished, 700,000 hectares of agricultural lands were wiped, more than a million people lost their home. According to Asia Development Bank and World Bank 2010: ''the direct damage caused by the floods was estimated to be US$6.5 billion, with an additional US$3.6 billion in indirect losses''. 

Image: S. Bajracharya, ICIMOD, Nepal. Source: State of Himalayan glaciers less alarming than feared (http://www.media.uzh.ch/en/Press-Releases/archive/2012/teilentwarnung-fuer-himalaya-gletscher.html)

Let’s first look at the nature of two relatively prevalent hazards in the Himalayas: Monsoon Floods and Outburst Floods

Monsoon Floods, as the name explains, are floods from the changes in monsoon rainfalls and cyclones, occur most frequently in the foothill area of Himalayan arcs, and low-lying areas in central and east Himalayan along the head of the Bay of Bengal. The change of the monsoon rain pattern as we discussed earlier is primarily from the physical atmosphere-ocean interaction together with regional or local topography variance, meanwhile, the surface-water flow and glacier runoff also depends on glacier mass (im)balance, with compounded contribution from anthropogenic effects such as land use change, deforestation, over-harvesting, illegal exploitation..etc

Outburst Floods, are the outburst of lakes at high elevation regions at altitudes of above 4000m, mainly referring to Glacier Lake OutburstFloods (GLOF). There are two types of GLOF, one is resulting from rapid collapse or overlapping of ice-dams which are formed by glacier itself, another is from water drains from the lakes which are formed at the shallow surface of a glacier or formed in a de-glacier basin, i.e. moraine-dammed and supraglacial lakes 

Credit: https://www.nap.edu/read/13449/chapter/4#46, Schematic diagram of a moraine-dammed glacial lake formed by glacial meltwater. Failure of the confining moraine dam leads to an outburst flood.

Climate Change and Glacier Lake Outburst Floods

Many research have come to a common ground to call for caution of a surprisingly rapid growth rate of glacier lakes caused by expected glaciers shrinkage, a warning of a greater variability and menacing flooding from potential glacier lakes outburst. 

As aforementioned, a glacial lake could be in place in a de-glacier basin, this is because as a glacier recedes from far end of its moraines, the moraines will become exposed, given moraines continue to remain high and stable with deposits of debris which were transported by the glacier in the early time, the melting glacier water will pond in the evacuated space creating by a retreating glacier between the moraine margin and end of retreating glacier, and then form a glacial lake. Once the confining moraine dam becomes weaker and eventually fails, which could be explained by a variety of trigger mechanism, for example water waves and pressures buildup by earthquake, rock sliding, avalanche, landslides, calving, coupled with weakening of moraine dam caused by seepage and enlargement of drainage conduits in the moraine, landslide, erosion and earthquake..etc, a GLOF will be initiated and having devastating consequences.

Source: ‘Glaciers online’ (http://www.swisseduc.ch/glaciers/himalaya/khumbu/imja_tsho/index-en.html?id=1) Imja Tsho moraine-dammed lake, Khumbu Himal, Nepal. The lake is seen from the right-lateral moraine, with lateral morainic trough on the right at a higher level. The lake still carries a winter ice-cover. 

Below two pictures are typical moraine-dammed lakes in the Nepal Himalaya from a recent research. Picture A is the largest lake in Nepal, Tsho Rolpa, holding over 100 million of cubic water which could fill 4000 Olympic-size swimming pools. Dig Tsho. Picture B presents the failure of confining dam in 1985 formed a GLOF causing catastrophic damage.

Credit: Google Earth. Source: Challenges Associated With Modelling Outburst Floods From Moraine-Dammed Glacial Lakes. 

By now, the natural hazards seem to come without warning, pose a threat without controlling, but is that the real case? Is the hazard really non-manageable? How are the academic institution researches progressing to go insight into the hazard assessment and mitigation? What are the governments of the countries of high vulnerability responding to the hazards cross the Himalayas ? Are they cooperative with or blaming each other? ......So please stay tuned for the upcoming posts :-)