Hydrology and Fluvial Geomorphology Case Studies and Facts

Question 1

Infiltration rates of clay vs sands

Answer 1

Infiltration rates of 0-4mm/h in clay, 3-12mm/h in sands.

Question 2

Cavitation fact

Answer 2

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.

Question 3

Cuspate delta example

Answer 3

Ebro Delta in Spain, which flows into the Mediterranean sea.

Question 4

Arcuate delta example

Answer 4

Nile delta, Egypt, which flows into Mediterranean sea

Question 5

Birds foot delta example

Answer 5

Mississippi Delta, USA,

Question 6

Abstraction fact

Answer 6

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…
.

Question 7

Physical causes of Mississippi flood 2011

Answer 7

Rainfall – 4x norm for April in US Midwest

Springtime snow melt - unusually high snowfalls in winter 2010-11 in upper Midwes

Question 8

Human causes of Mississippi flood 2011

Answer 8

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?

Question 9

Physical causes of Boscastle flood 2004

Answer 9

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

Question 10

Human Causes of Boscastle flood 2004

Answer 10

Bridge – obstructed course of river (cars & vegetation became stuck)
Lack of flood control system
Old sewer & drainage systems (small capacity)
Not prepared

Question 11

Warning time fact

Answer 11

over 50% of unprotected dwellings in England and Wales have less that 6 hours of flood warning time.

Question 12

pakistan flood key facts

Answer 12

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

Question 13

pakistan flood Physical causes

Answer 13

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

Question 14

Pakistan flood human causes

Answer 14

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

Question 15

Socal impacts of pakistan flood

Answer 15

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)

Question 16

Economic impacts of pakistan flood

Answer 16

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%

Question 17

Environmental impacts of pakistan flood

Answer 17

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.

Question 18

preparation of Pakistan flood

Answer 18

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)

Question 19

Short term relief of Pakistan flood

Answer 19

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.

Question 20

Future prevention from Pakistan flood

Answer 20

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

Question 21

Afforestation fact

Answer 21

40,000 trees planted in Pickering, Yorkshire 2016 =>reduced peak flow by 20% after 50mm rain fell in 36 hours

Question 22

Land use zoning fact

Answer 22

curitiba, Brazil has built parks with artificial lakes along rivers which flow through the city hence impact of flooding is minimised.

Question 23

Dredging fact

Answer 23

Mississippi river is constantly dredged in order to maintain a 2.5m depth in the lower course.

Question 24

Channel straightening fact

Answer 24

Between 1934 and 1945, a 530km stretch of river mississippi was shortened by almost 300km.

Question 25

levees fact

Answer 25

over 4500 km of the mississippi river have levees, averaging 7m in height

Question 26

3 gorges dam facts

Answer 26

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)

Question 27

Oxbow lake example

Answer 27

Carter Lake, Iowa. From the mississippi river

Question 28

Waterfall and gorge example

Answer 28

Victoria falls and the zambezi gorge.

Question 29

braided river example

Answer 29

Tasman River,, New Zealand. Flows from the glaciers of Mount Cook