Causes of flooding
It can be devided into 2 kinds. Natural and Manmade.
Natural Causes of Floods:
Heavy rainfall raises the water level. When the water level is higher than the river bank or the dams, the water comes out from the river,there will be flooding.
Because of global warming, the temperature of this year is higher than the temperature of many years ago.The ice caps melt in spring, and the water goes into the sea. The water raises the sea level, and makes the river level rise. When river level rises, flooding may occur.
Flooding often occurs in lowlands. This is because rivers flow more slowly in low-lying areas. If the water volume increases suddenly, floods occur.
Flooding always occurs in coastal areas. High tides or storms cause the water level to rise. If the water level is higher than the level of the coastal lowland, flooding will occur.
Human Causes of Floods
Large areas of forests near the rivers have been cleared. The lands are used to make room for settlement, roads and farmland. Less vegetation protects the soil, the soil is quickly lost to rivers and the sea.This raises the river bed, so the river overflows its banks easily.
Some farming practices can damage the vegetation cover, so the soil will be washed into the river easily.
People want more food and money. They graze too many animals on the land and the pasture is eaten away quickly. Less vegetation cover results in soil washed into the rivers easily.
When a piece of land has been used for farming for a long period of time, the soil may became so infertile that no vegetation can grow on it. The land is less fertile than before so the soil washed into the rivers more easily
3.Poor water management
When the dams are poorly constructed or maintained ,they can easily collapse and this results in flooding. Moreover, poor plan of city construction can also cause flooding as the water can't flow out easily.
Because of large amounts of people, everything needs more, like wood, land and food……
Soil erosion happens more often and increases the risk of flooding.
Causes of flooding in Thailand
Main cause of flooding in Thailand is heave rain in monsoon season, overloaded capacity of dam, river. Geographical of Thailand, Northern Thailand is hill side, when there is heavy rain the water flow from northern river such as Ping, Wang, Yom, Nan to Chaopraya river, flood-plain area which is central area. When Kangsuaten dam and Naresuan dam are at full capacity, the water is released to central region to Pasakjolasit dam, if Pasakjolasit dam reach full capacity water will be released to lower region of Chaopraya river. Therefore flood happen.
Due to climate change, it become harder to predict the amount of water each year. There are about 6 main dams in central Thailand; only 3 of them were built to retain water. In 2010, first six month of the year Thailand face drought, so most of the dams retain water up to 90% capacity, when heavy rain occur dam capacity was full, flooding occur.
Urbanization, the flood-plain areas that used to be the area to retain water were cover up to support unwell plan expansion of the city, block the natural drainage mechanism.
Lack of cooperation between government’s organizations, some project may be an obstacle for other project. Government should issue clear regulation for usage of land in flooding area as a long-term prevention, not just some relief plans after floods occur.
Effects of flooding
Thailand is under influence of monsoon, leads to heavy rain 1000-4000 cubic meter per year, 80% of rain is in rainy season (May - October) which flood likely to occur. Importantly, low land which is risky to flood are situated in the lower region of Chaopraya river include 9 provinces, 16.2 million residence, economic size is 44% of GDP. Thai people use 5% of water to consume, 5% for industry, and 90% for agricultural. In 2010 severe tropical storms, heavy rains and flash floods since mid-October have affected two-thirds of the country. The north-eastern provinces were the first to be hit, followed by the central and southern provinces. According to the government, the natural disaster has so far affected 13.4 million people in 51 of the country's 76 provinces, claimed at least 229 lives and forced the closure of some 3,441 schools.