The human impact Flashcards

Question

Dam Construction

Answer 1

Multi-purpose Controlled release of water - removed flood risk entirely Effectiveness depends on relative scale Removes sediment causing clear water erosion, deepening the channel

Answer 2

They trap and store water so reduce surface runoff as water is released in a controlled way The reservoir lake can be used for recreation e.g. fishing Very effective

Answer 3

If the land upstream of dam is flooded, ecosystems change and residents may have to move Trap sediment that would normally flow downstream and farmers rely on silt providing fertile soil after flood events Very expensive

Answer 4

Water from a too-high body of water spills into pipes which carry the water into a storage reservoir

Answer 5

Effectively increases bankfull capacity and diverts flow away from high impact / risk zones Requires space on floodplains so not always possible

Answer 6

Water can be pumped out of the river and stored in temporary lakes, or diverted during times of high flow Pumped back in when discharge in river drops Low impact zones can be recreational land use Flood water will evaporate or eventually infiltrate, replenishing groundwater supplies

Answer 7

Need a large area of available land

Answer 8

Levees built along the whole length of the river 27 control dams built upstream and 100 dams built along the Mississippi's tributaries and reduce pressure on levees Channel straightening and channel lining took place River shortened by over 250km $7bn spent over 100 years

Answer 9

Involves the use of the natural environment

Answer 10

Afforestation at upper catchment zones increases interception and reduces surface runoff Lowers peak discharge and increases lag times

Answer 11

Ploughing along contours of a field to reduce surface runoff More suitable to Europe

Answer 12

Increased water infiltration and soil moisture storage so less overland flow Easily manageable and a cheap solution

Answer 13

Heavy rain causes ground to become saturated so when there is peak rainfall the precipitation hits the ground and runs off into the river anyway Gradient of slope helps increase velocity of runoff Land owners may not agree to have their land ploughed along the contours

Answer 14

Strip cropping to vary interception and surface runoff Stores water as surface water Vertical ploughing technique Used in Asia as it is better for growing rice

Answer 15

Can prevent flooding from the source of the river Often is cheap

Answer 16

The gradient of the land can increase velocity of surface runoff

Answer 17

Aim to restore the river's natural processes of erosion and deposition May use floodplains for water to overflow into, all hard engineering removed, meanders re-dug Complete survey completed to ascertain river's natural course, then attempt to chive it through mechanical engineering

Answer 18

New meanders can hold more water, therefore reducing the risk of floods as there is more room in the river for floodwater Cheap

Answer 19

Need space for a large floodplain Flooding still occurs when water moves at high speed Needs high investment

Answer 20

Example of river restoration scheme 85,000 cubic metres of water can now be stored as the park was lowered and reshaped to create a floodplain capable of storing large volumes of water Made to provide additional flood storage through ponds and lakes, simultaneously creating an attractive open space Visits have increased by 73% New habitats built by introducing wetland pond areas so biodiversity increased

Answer 21

Improved use of weather satellites and radars can reduce flood damage by up to 40% Data on rainfall and stream discharge produce accurate predictions of flood surge times Can be used for authorities to organise evacuations or communities to prepare for floods

Answer 22

People don't always listen Warnings may not be received, like in rural areas of LICs Not always possible as flash floods have too short a lag time It is usually much less sophisticated in LICs so they are more likely to be affected by floods

Answer 23

The prohibitive zone No further development is allowed except for essential waterfront facilities

Answer 24

The restrictive zone Only essential development and recreational activities are permitted - all buildings should be waterproof

Answer 25

The warning zone Inhabitants receive warnings of impending floods and are reminded regularly of the flood hazard

Answer 26

People can live close to a river but not be affected by floods (unless extreme ones occur) Cost is minimal and once put in place requires little management

Answer 27

No hard structures to prevent flood water so the scheme is flawed when there is heavy rain and high velocity in river Can only be put into place in an area of the river which hasn't been built up Can't be used where floodplain has already been built up

Answer 28

80% of Bangladesh is in the delta of 3 rivers - Ganges, Meghna and Brahmaputra so when snowmelt occurs in late spring, early summer, flood risk increases due to high peak discharge Low lying country with most of it between 5 and 8m above sea level with some coastal areas less than 1m above sea level 70% of land is farmland so vegetation which could intercept surface runoff has been removed Upper courses of rivers are in other countries so Bangladesh can't build dams upstream which could prevent flooding downstream High corruption (149 / 180) and low GDP per capita ($2,600) so much of the little money the country has is pocketed and not spent on flood prevention

Answer 29

40% of Dhaka underwater 800 deaths and 30m people made homeless 100,000 people in Dhaka suffered from diarrhoea due to dirty water 900,000 families lost their home 3m experienced damage to housing

Answer 30

9m made homeless 1,000 died from drowning and water-borne diseases 1,100 deaths in total 10.5m displaced 100,000 cases of dysentery and diarrhoea 52 villages in 40 districts affected

Answer 31

8m affected and 150 deaths 104,000 houses ruined and 630,000 partially damaged 1,000 schools closed and 4,300 schools were damaged 450,000 hectares of farmland flooded

Answer 32

Cost of flood damage was $2.3bn 2m acres of agricultural land submerged 5,000km of road destroyed 3,919 livestock dead

Answer 33

2.2m acres of damaged cropland $290m of crops damaged Total economic loss was $1.3bn $7bn in damage to schools and hospitals

Answer 34

21.49% reduction in annual earnings 90% of crops damaged in Sunamganj district Rice price increased by 30% Damaged 220,000 hectares of crops with 16,000 hectares fully lost and 560,000 hectares were partially damaged

Answer 35

53,000 hectares of agricultural land was flooded Many fish could be seen floating from the flooded ponds and reservoirs so habitats were destroyed Water couldn't drain due to the soil already being saturated from a flood the month before

Answer 36

Kaptai Dam built in 1962: Stores 6,477m cubic metress Cost $22.5m Produces 230 MW - 5% of national electricity Funded by US Agency of International Development (USAID) Displaced 100,000 indigenous people Submerged 54,000 acres of farmland

Answer 37

Started in the 1960s Aimed to protect coastal zone from storm surges Manages the area's water flow Cost around $150m (funded by World Bank) 4,000km of embankments along coastal areas 139 polders built to protect agricultural land Manages up to 4,500 cubic metres per second Provides irrigation to 111,406 hectares of farmland Planning to generate 67.5 MW Flooded in October 2023 due to heavy rains in India causing a dam to release excess water

Answer 38

Shields 88,000 hectares of farmland from flood damage every year River erosion is prevalent - 15 km of embankment within 300 m of river and 70 km within 500 m 600 m of erosion can take place annually Phase 1 has $650 m in funding from World Bank to upgrade 50 km of embankment 200 kg sand-filled geobags reduced erosion to 3,300 hectares per year from 6,300 in the 1970s Heavy rain in summer 2020 breached the new embankment showing limits in current defences

Answer 39

Slurry of grass seed, mulch, fertiliser and blonding agents is sprayed onto the ground so germination takes place quickly and so form grasses with roots Grassroots reduce risk of landslides as they hold topsoil together This means water flowing through soil will not transport as easily even with higher saturation Protects homes and infrastructure

Answer 40

A quarter of Bangladesh's cultivated land is for rice farming Predominantly takes place in the south, closer to the coast This makes the region more susceptible to salt water from the sea from floods and tidal surges so more saline soil conditions Boro, the rice crop planted in 90% of these regions, suffered from drought and high saline soil From 2020, 2 new rice variants have been introduced which perform better in such conditions The 2 GM crops take 150 days to mature and produce 7 tons/hectare in ideal conditions and 5 tons/hectare in saline conditions Yields are 30% higher as a result

Answer 41

Replacement for chickens more and more in Bangladesh as they can drink floodwater and float on top of floodwater They produce similar meat

Answer 42

Intercept precipitation and transfer some back to the atmosphere via transpiration Lots of water stored inside is used for biological processes so it doesn't reach the ground Tree roots slow infiltration and absorbed water flows slower so higher lag times from precipitation to higher river levels occurs 90% of water in Bangladesh originates outside the country, making this strategy hard to implement

Answer 43

USAID and NASA are helping Bangladesh's government by increasing flood warning time from 5 days up to 8 days The solution involves a satellite circling the earth Since 90% of water originates outside the country, data on how much water will flow into the country is hard to get Satellites are now being used to measure the distance between the satellite and the river surface where the satellite crosses above Bangladesh This reveals the river's height at point of crossing so flood risks downstream can be assessed quicker

Answer 44

Set up in Bangladesh to help mitigate the effect of flooding Uses global flood awareness system (GloFAS) to better predict flood events

Answer 45

Flood hazard maps are developed using 8 physical indicators for flood contributing factors such as elevation, slope and rainfall Organises hazard risk information and offers visual depictions of possible hazards They have identified that 68% of the country is vulnerable to river flooding while 25% is at risk of tidal flooding This has helped guiding urban development and managing land use as they know where is likely to flood Over 50 million people benefit from the system as warnings are issued 5-10 days in advance

Answer 46

Flood Forecasting and Warning Centre (FFWC) has created the Early Warning System (EWS) in Bangladesh to protect people from flooding Challenging as most of the country is poor and without internet access Mobile companies like Deltares are putting in place two new methods: Voice Message Broadcast (VMB) to issue warnings from national to local scale and Short Message System (SMS) to collect water level data from locals to help discover possible flood threats