To what degree are human factors responsible for flooding?
Case Studies: * Mississippi 1993 (HIC - OECD) * Bangladesh 1998 (LIC)
There are various causes and consequences of flooding, from displacement to death. But flooding, which is defined as being ‘the overflowing of a body of water onto dry land’, is enhanced by human intervention. Apart from natural causes; rainfall. Humans, in development, conquest to disturb the environment. Human factors such as urbanisation, changing of river systems (e.g. the building of levees, channel straightening etc.) are all important in the causes and consequences of flooding. * Firstly, there is the issue of deforestation; the cutting down and removal of trees. Deforestation means that there is less vegetation for the interception of water, meaning that there is a larger amount of surface run-off, while deforestation also results in the loss of top-soil, and therefore the inability for new trees to grow. Since 1990, Bangladesh has lost a total of 2,600 hectares (ha) of forest cover per year, this equates to 0.17% of all forest cover in Bangladesh, meaning that by 1998, there would be an average loss of 20,800 ha of forest, this is contrasted in the US, where afforestation is taking place due to Flood Action Plans by the Tennessee Valley Authority (TVA). * Secondly, urbanisation. 82% of the United States’ population lives in urban conditions, while the 1990 US census shows that in Mississippi State alone, there was 49% urbanisation. Let alone this and discounting the 31 states covered by the Mississippi-Atchafalaya River Basin (MARB), the 12 states that the Mississippi river basin comprises of: Arkansas; Illinois; Indiana; Iowa; Kentucky; Louisiana; Minnesota; Mississippi; Missouri; Ohio; Tennessee and Wisconsin, have a combined average urbanisation of 60.8% with an annual increase of 1.2% (overall). Similar to this, urbanisation rates in Bangladesh remain low at 28.4% though the annual increase rate is much higher at 2.96% per annum. An increased level of urbanisation means that permeable ground is covered over by tarmac and concrete which means that rates of infiltration drop while surface run-off rates increase. This enables water to reach the river at a much faster pace, and in bulk. This is aided by drainage and sewage systems which transport water directly to the river causing mass displacement, and an increased discharge which then results in flooding. In addition to this, urbanisation means that new industry is put into place, which results in increased water pollution, as factories are often on river banks – easy access to water – which means that most if not all of their chemical and human wastes are deposited into the river. * Another human factor for flooding is hard engineering; which is often defined as the disruption of natural processes by the use of man-made structures. Examples include channel straightening, dredging, dams, reservoirs, and levees. It is said that there is a 3,500 mile levee system, and while this provides protection, there are also non-federal levees, which run the risk of over flooding, and scourging. Furthermore, the St. Louis tributary channelling caused water to flow downstream at a much faster velocity that otherwise, which means that discharge is higher downstream, causing flooding. * Global warming, is caused by the emission of carbon gasses amongst other things. The Brahmaputra River’s discharge is increased significantly due to snow melt in the Himalayas. This is indirectly caused by mass carbon emission; In 1994, Bangladesh’s estimated CO2 emission without the addition of Land use and forest cover (LUCF) changes adds up to a total of 16,459.7 metric tonnes, while the country’s estimated usage with LUCF adds up to 24,297.7 metric tonnes. Moreover, the total Greenhouse gas emissions in 1994 without LUCF add up to approximately 45,926.2 metric tonnes while the total GHG emission with LUCF adds to approximately 53,764.1 metric tonnes. This equates to an approximated increase of 8.6% per annum (from 1994 to 2005 (latest available years data.))

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[ 1 ]. http://data.worldbank.org/country/united-states
[ 2 ]. http://data.worldbank.org/country/bangladesh
[ 3 ]. http://rainforests.mongabay.com/deforestation/2000/Bangladesh.htm
[ 4 ]. http://www.census.gov/prod/cen2010/cph-2-26.pdf - Table 1
[ 5 ]. http://water.epa.gov/type/watersheds/named/msbasin/marb.cfm
[ 6 ]. http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcsdev11_023950.pdf
[ 7 ]. http://www.census.gov/population/censusdata/urpop0090.txt
[ 8 ]. https://www.cia.gov/library/publications/the-world-factbook/fields/2212.html
[ 9 ]. https://www.cia.gov/library/publications/the-world-factbook/fields/2212.html
[ 10 ]. http://www.mvd.usace.army.mil/About/MississippiRiverCommission(MRC)/MississippiRiverTributariesProject(MRT)/LeveeSystems.aspx
[ 11 ]. http://unfccc.int/files/ghg_data/ghg_data_unfccc/ghg_profiles/application/pdf/bgd_ghg_profile.pdf - Table 1
[ 12 ]. http://unfccc.int/files/ghg_data/ghg_data_unfccc/ghg_profiles/application/pdf/bgd_ghg_profile.pdf - Table 3