River Mersey Flashcards
local river catchment study
river mersey
river catchment
flows for 70 miles from its source at confluence of river tame and goyt in stockport
flows westwards through suburban areas of manchester heads north between liverpool and birkenhead where its mouth is in the liverpool bay
our study area
upper catchment of the river mersey is above gauging station at ashington weir
- 15 miles north west of sale
- 93 miles north east of carrington
characteristics of the mersey upper catchment
- catchment is made up of river mersey, tame, goyt, bollin and sunderland brook.
- catchment has a mix of predominantly rural uplands with lower catchment highly urbanised
- history of flooding with 2600 properties at risk
how would the geology of the catchment impact upon the local water cycle?
- west- moderate permeability
- upland areas allow for groundwater and throughflow which allows for steady flows of water back to river
- in east bedrock is permeable however majority of this area is now urbanised so no longer permable
how would the rainfall of the upper catchment impact upon the local water cycle?
highest rainfall in east where rural higher areas - indicating relief rainfall
rainfall across catchment is higher than uk average rainfall has increased from 1941-1970 - 1961-1990 due to increased precipitation and climate change
how does land use of the upper catchment impact upon the water cycle?
west of the area is heavily urbanised resulting in impermeable surfaces
east are mountains and bog areas the area correlates to permeable rocks meaning lots of infiltration and percolation into underground rocks
how have people impacted upon the local water cycle?
- major management and modification of the river system
- in urban areas many water cources have been cultivated or channelised
- manchester ship canal recieves water from upper mersey and is an important drainage and flood alleviation system
how have people impacted on local water cycle?
- Mersey catchment - operational washlands provides a valuble flood risk management - means river can flood naturally
- area has 83,000 people and 70% live in upper Mersey catchment
Flooding
urban areas south of manchester infiltration rates have decreased massively
1965 - largest flood
need to manage the area due to high proportion of catchments population living in area
levels in the river
highest levels most recently are linked to climate change
causes of flooding
upper catchment is steep and heavily urbanised response time of river = 2 hours (fast) which can result in flooding
surface water flooding is known to occur in urban areas of this catchment. it is a result of short intensive storms when the capacity of the urban drainage system is exceeded
which places are at a greater risk of properties being flooded?
areas at greatest risk = most urbanised sale stockport didsbury uppermill
management of the catchment?
20 million pounds has been invested in last 10 years on developments of flood illeviation
over 67km of raised flood defences
3 flood storage areas
activities that reduce the probability of flooding include?
flood risk mapping - understanding where flooding is likely to occur
operation of floodline and warning services
