Lecture 13.2: Effects of Floods (Socio-Economic (Disruption of Svcs (impt…
Lecture 13.2: Effects of Floods
Disruption of Svcs
impt urban sectors like urban infra, trade etc. hampers econ productivity during & after floods
e.g. August 2014 Nepal floods: 21,000 fams affected as access to them cut off by damaged roads.
gas & electricity: disruption of daily activities, temporary closure of factories & industries to fire & explosion
transportation: food & cleaning supplies shortage-> starvation in LDCs.
Spread of Diseases
e.g. Feb/Mar 2000 Mozambique floods: nearly 2000 cases of cholera, 100s of cases of malaria
gastro-intestinal diseases break out in LDCs w/ low sanitation standards/damaged sewer systems-> drinking H2O polluted, esp. if sewerage treatment plants are flooded
dehydration (little to no access to clean H2O) + disease epidemics
Loss of Lives
flood management measures can still fail in DCs e.g. 2005 Hurricane Katrina killed nearly 2000 ppl in New Orleans due to levee failure
by drowning, diseases, structural damages
claim 20,000 lives worldwide annually
Environmental effects: more '+' than '-'
Impact on Eco-system
high magnitude floods can sweep plants away, drown animals-> loss in wildlife & biodiversity
maintain ecosystems by providing breeding, nesting, feeding & nursery areas for fish & shell fish
infiltrating & percolating floodH2Os recharge H2O table, provides LT H2O supply to plants
Dispersal of Nutrients & Pollution
destruction of buildings that contain toxic materials (pesticides, gasoline etc.) can cause release of these materials
cause pollution esp. in urban areas. disrupt normal drainage systems, overwhelm sewer systems-> raw/partially raw sewage spills.
deposited alluvium helps keep elevation of land mass above sea lvl. e.g. b4 dams & levees were built along Mississippi river, floods would deposit sediments on delta. w/o continued replenishment, delta is subsiding @ abt 100km2 yearly
Socio-economic effects: geographically uneven. e.g. in DCs, deaths declining but 3/4 of property losses from floods occur due to extensive built-up areas. in LDCs, higher death rate due to inadequate flood management systems & pop. pressure which causes ppl to settle in floodplains
Damage/Loss of Property
when floodH2Os retreat, v much lower, deposition occurs. everything covered in mud, including building interior-> huge cost of cleaning & damages
e.g. in rural Bangladesh, houses w/ mud/tin walls in slums can collapse. 32% of pop. lives in slums so many left homeless.
high v of H2Os transport larger particles as suspended load. can undercut & erode foundation of buildings, bridges, levees-> collapse or need repair. displace ppl from homes.
Agriculture & Livestock
maintains soil fertility by depositing layers of alluvium & flushing salt out of soils-> better harvests
LT '-' impact is topsoil erosion. topsoil is where decomposition & nutrient cycling happens. erosion results in reduced productivity of land (less nutrients supplied)-> abandonment
countries w/ large agrarian economies like Nepal affected most. e.g. in Bangladesh, agriculture forms 18.6% of GDP, employs 45% of labour force.
drowning of crops, livestock & damage to infra