58 of the 77 provinces in Thailand have been hit by severe river flooding over the past few months, causing over 200 deaths and affecting 2 million people. The majority of the flooding has come from the Chao Phraya river and its tributaries which has a watershed covering 35% of Thailand, about 61,000 square miles!
Causes
The main cause of the flooding is the excessive rainfall during this years monsoon season exceeding the rivers capacity. Some areas of Thailand can expect to receive 2,400mm of precipitation per year, most of which falling between September and December. However, this years monsoon season in the Chao Phraya basin started about a month earlier and was significantly heavy than normal. Thailand can expect to well exceed its 2,400mm of precipitation this year. Thailand has insufficient methods of dealing with this extremity. The only provisions that have been taken are a series of 3 dams on the Chao Phraya – The Kangsuaten, Naresuan and Pasakjolasit dams. The problem with this is that the 3 dams do not have the capacity to cope with the quantity of rainfall in the Chao Phraya that Thailand has experienced over the past months.Also, there has been a higher level of snowmelt from high lands inland from Thailand at the Chao Phraya source. This is due to higher temperatures that some scientists would blame on global warming. Global warming has also been blamed for the high temperatures causing droughts in the dry season. This has a knock-on effect to flooding during the rainy season since the heat bakes the soil, reducing the infiltration, increasing surface run-off and reducing lag time. Also, the dams ‘stockpiled’ water due to the drought, so at the start of the monsoon, the dams were already 90% full.
Finally, humans can also be directly blamed for a number of reasons. Firstly, deforestation for the building of settlements, roads and farmland has reduced the vital interception that slows down the process of water reaching the rivers. With less vegetation cover, less water is intercepted, surface run-off increases as water cannot infiltrate quick enough and lag time is reduced. Also, deforestation and poor farming techniques allow loose sediment to flow into rivers as soil erosion is more likely on bare soil. This deposits on the river bed, decreasing the depth of the river channel, increasing the likelihood of flooding.
Effects
- Over 200 deaths.
- 500,000 people put into emergency accommodation within 1 week of flooding.
- The USA have given $100million to help flood victims.
- Some farmers started ‘emergency harvesting’ prior to floods destroying them, however 87,000 tonnes of crops have been destroyed.
- 3,441 schools have closed.
- Spreading of disease such as cholera.
What Can Be Learnt From This?
I think that Thailand and the world can learn a lot from this event. It is clear that Thailand, along with the rest of the world is going to experience much more extreme weather and climate patterns as an effect of global climate change and that we will need to deal with these effects. Thailand clearly needs to improve its system of flood defences. If the reservoirs were nearly empty at the beginning of this monsoon, then the effects of this flooding may have been much more localised. This is an obvious insight to how humanity will have to change its ways to live with a rapidly changing environment and increasing population. The suggested management options in a 2010 report from the RID (royal irrigation department) have mainly involved hard engineering methods. Some of those recommended are dredging and widening the Chao Phraya and its tributaries, constructing more dams and water stores, and creating passageways to allow water to flow to the sea quickly, reducing lag time. However, these would be economically and socially expensive. Flooding has been becoming progressively worse over the past century in Thailand, so does this provide evidence for humans causing global climate change? I think it does, mainly due to the fact that the flooding has increasingly worsened since industrialisation and development as our carbon emissions began to rocket. This cannot purely be coincidence since flooding of this nature was rarely experienced prior to 1900.
