Hydrology and Fluvial Geomorphology Case Studies and Facts Flashcards
Infiltration rates of clay vs sands
Infiltration rates of 0-4mm/h in clay, 3-12mm/h in sands.
Cavitation fact
the implosion of trapped air bubbles, a process which evicts tiny jets of water with velocities of up to 130ms-1 which can weaken solid rock.
Cuspate delta example
Ebro Delta in Spain, which flows into the Mediterranean sea.
Arcuate delta example
Nile delta, Egypt, which flows into Mediterranean sea
Birds foot delta example
Mississippi Delta, USA,
Abstraction fact
in the USA 20% of irrigated land is fed by groundwater = groundwater depletion is widespread = water scarcity
BUT in London water table fell by 30m during industrialization, but is now rising by 2m a year since closure of heavy industry = threats to basements, tunnels, foundations…
.
Physical causes of Mississippi flood 2011
Rainfall – 4x norm for April in US Midwest
Springtime snow melt - unusually high snowfalls in winter 2010-11 in upper Midwes
Human causes of Mississippi flood 2011
Urbanisation – e.g. Memphis Tennessee
Levees constrict flow of river, forcing water to travel downstream faster (levee war)
Heavier rain & melting of snow – climate-change induced?
Physical causes of Boscastle flood 2004
Heavy rainfall (89mm in an hour)
Storms leading up to flooding on 16th August (saturated ground – high antecedent rainfall)
Relief rainfall (Bodmin Moor)
High temperatures => high evaporation
Coastal location: moist winds off sea
Steep relief of valley sides (Valency valley)
Narrow river channel in village itself
Human Causes of Boscastle flood 2004
Bridge – obstructed course of river (cars & vegetation became stuck)
Lack of flood control system
Old sewer & drainage systems (small capacity)
Not prepared
Warning time fact
over 50% of unprotected dwellings in England and Wales have less that 6 hours of flood warning time.
pakistan flood key facts
Date: July 2010
Location: monsoon rains in the Khyber Pakhtunkhwa, Sindh, Punjab and, Balochistan regions affected the Indus River basin. => 1/5th of Pakistan’s land area affected
pakistan flood Physical causes
Heavy monsoon rain; Khyber Pakhtunkhwa (KPK) has 60 hours of continuous rainfall.
Monsoon hit northwest region; more mountainous = increased runoff = decreased lag time. High Drainage density and convergence of many tributaries = decreased lag time.
Climate Change; Higher water surface temperature in Bay
of Bengal = increased evaporation = driving heavier monsoon
Pakistan flood human causes
Deforestation; Only 5% is covered by forests. Swat valley suffered deforestation from illegal logging whilst under taliban control pre 2009 => less interception and greater runoff.
Levees; In Sindh levees had been constructed around the river channel, but these were breached = flooding of surrounding area = water unable to re-enter channel
Socal impacts of pakistan flood
Short term
1,781 deaths.
1.2million homes damaged or destroyed. => 1 million people displaced
Medium term
Destruction of healthcare infrastructure and pollution of water = case of cholera emerged by 14th august
Long Term
Long term closure of schools and hospitals. (10,000 schools and 500 hospitals swept away)
Economic impacts of pakistan flood
Short Term
Destruction of Karakoram Highway, connects Pakistan to China.
Medium Term
£1.5bn agriculture loss as 23% of crops destroyed and 1.2mn livestock died=> tripling of food prices due to shortages
Long Term
Total damaged estimate at $43bn
The GDP growth rate of 4% prior to the floods turned to −5%
Environmental impacts of pakistan flood
80% of reptile and small mammal habitats were effected within the Swat and panjika river catchments due to inundation by contaminated flood waters.
Mangroves revived as water and nutrients reached previously diminishing mangroves due to the construction of Tarbela dam on Indus River.
preparation of Pakistan flood
Construction of levess in Sind to help prevent flooding by increasing the capacity of the Indus channel.
Pakistan Meteorlogical Department began tracking storm in Bay of Bengal in mid July. PMD issued flood warning to KPK province on 24th July, BUT warnings were not taken seriously enough by regional authorities, media and residents hence no evacuations of management. (because KPK assumed no flood as no big flood in living memory)
Short term relief of Pakistan flood
A year after the floods, international aid totaled $1.3billion.
BUT The Disasters Emergency Committee’s UK appeal raised £40m in the first month. But much less than for the Haiti earthquake only seven months earlier (£77m) despite larger scale of disaster. Due to time of year; people on holiday, perception of extremism from Taliban, long time scale of flood vs an earthquakes sudden impact, donor fatigue.
352,000 people rescued by pakistan navy BUT hundreds of thousands of military personnel were involved in fighting the Taliban in NW therefore not diverted to help with flood relief
Pakistan government was criticised by some for its response efforts. Many saw it as slow, disorganised and corrupt as some areas where given preferential treatment. (with some politicians diverting helicopters, food and medicine to their constituencies at the expense of others.)
In August President Asif Ali Zardari went on a 10-day trip to europe, furthering perception that Pakistan’s leaders were indifferent to flood victims’ suffering.
He also failed to declare a national state of emergency slowing responses
300,000 refugees in Sind province’s 20 refugee camps, but these were soon full.
Future prevention from Pakistan flood
RAMSAR advised on anti-flood improvements;
Upgrading flood warning system
Fourth national flood prevention plan initiated (2015-2025)
Plans to integrate soft measures and flood management:
Protect upstream forests
Map floodplains
Large reservoir construction
Estimated flooding in 2030 will affect 56mn people in pakistan
Afforestation fact
40,000 trees planted in Pickering, Yorkshire 2016 =>reduced peak flow by 20% after 50mm rain fell in 36 hours
Land use zoning fact
curitiba, Brazil has built parks with artificial lakes along rivers which flow through the city hence impact of flooding is minimised.
Dredging fact
Mississippi river is constantly dredged in order to maintain a 2.5m depth in the lower course.
Channel straightening fact
Between 1934 and 1945, a 530km stretch of river mississippi was shortened by almost 300km.
levees fact
over 4500 km of the mississippi river have levees, averaging 7m in height
3 gorges dam facts
Three Gorges Dam, China along the Yangtze River.
(87 TWh per year)
flood storage capacity in reservoir of 22cubic km) e.g in August 2009 the dam limited the water flow to less than 40,00cubic m per second.
Chinese River Dolphin now extinct)
displaced 1.3mn people)
(US$ 22.5 bn)
Oxbow lake example
Carter Lake, Iowa. From the mississippi river
Waterfall and gorge example
Victoria falls and the zambezi gorge.
braided river example
Tasman River,, New Zealand. Flows from the glaciers of Mount Cook
