HB RR Flashcards
1
Q
River Processes include (3 stages)
A
Erosion, transportation and deposition
and all depend on the amount of energy in the river.
2
Q
Erosion happens near its source. Surface run-off and throughflow cause erosion at the point where the water enters the valley head. This erosion is called
A
Headward erosion
3
Q
Gravity and the weight of water flowing downhill – causes erosion of the bed and banks making the river wider, deeper and longer - erosion caused by
A
The energy in a river
4
Q
Erosion that makes a river channel deeper. This happens more in the upper stages of a river
A
Vertical erosion
5
Q
Erosion that makes a river wider. This occurs mostly in the middle and lower stages of a river.
A
Lateral erosion
6
Q
There are four main processes of erosion that occur in rivers. These are:
A
- hydraulic action
- abrasion / corrasion
- attrition
- corrosion
7
Q
The force of the water hits river banks and then pushes water into cracks. Air becomes compressed, pressure increases and the riverbank may, in time collapse breaking away rock particles from the river bed and banks
A
Hydraulic action
8
Q
The sediment carried by a river scours the bed and banks. Where depressions exist in the channel floor the river can cause pebbles to spin around and turn hollows into potholes.
A
Abrasion / Corrasion
9
Q
River water is swirled around in irregularities in the river bed creating
A
vertical eddies
10
Q
Rocks get swept into small depressions and abrade the hollow. These rocks are called
A
Grinders
11
Q
Eroded rocks collide and break into smaller fragments. The edges of these rocks become smoother and more rounded.
A
Attrition
12
Q
Carbon dioxide dissolves in the water to form a weak acid which dissolves rock by chemical processes, particularly where carbonate rocks such as limestone and chalk are present in a channel. This can lead to characteristics like sink-holes, pot holes, caves and gorges.
A
Corrosion / Solution
13
Q
Transportation of material in a river begins when it has been loosened by erosion is transported along the river. There are four main processes of transportation. These are:
A
- suspension
- solution
- saltation
- traction
14
Q
Very fine particles of material such as clay and silt are lifted as the result of turbulence and transported by the river
A
Suspension
Faster-flowing, turbulent rivers carry more suspended material making the river appear muddy
15
Q
Dissolved minerals are carried by a river.
A
Solution
This often happens in areas where the geology is limestone and is dissolved by slightly acidic water
16
Q
Material like pebbles and gravel that are too heavy to be carried in suspension bounce along the river by the force of the water
A
Saltation
17
Q
When large materials such as boulders are rolled and pushed along the river bed by the force of the river
A
Traction
Sometimes this only happens when the river is in spate or very full and not at other times.
18
Q
The total load a river can transport at a given point
A
The capacity of a river
19
Q
The process of the eroded material being dropped when a river loses energy
A
Deposition
20
Q
A river can lose its energy when (5)
A
- Rainfall reduces
- Evaporation increases
- Friction close to river banks and shallow area
- Flatter areas
- Meets the Sea
21
Q
The Hjulström curve shows the
A
relationship between river velocity and competence
It shows the velocities at which sediment will normally be eroded, transported or deposited
22
Q
The maximum particle size of load a river is able to carry at a particular point
A
The competence
23
Q
The total volume of material a river can transport
A
The capacity
24
Q
Energy in a river is determined by three factors:
A
- mass of water
- the height of the river above sea level
- the gradient of the channel
25
Friction with the bed and banks and turbulence reduces
energy
26
Water with a more turbulent flow can transport more
sediment
27
Velocity is affected by three main factors:
1. channel slope
2. roughness of the channel’s bed and banks
3. channel shape in cross-section (width)
28
canalise rivers with concrete walls to get them to move the water away from vulnerable areas quicker but this can actually cause other problems up or downstream such as (2)
siltation or flooding
29
A range of river elements can be measured. These include (5)
1. changes in depth and width of rivers
2. the type of bed load (size/roughness etc)
3. stream gradient
4. channel profiles
5. channel and flow characteristics
30
The long profile of a river shows
changes in the height (altitude) of the course of a river from its source to its mouth
the slope becomes more gentle towards the mouth of the river. Long profiles usually have irregularities such as waterfalls or lakes.
31
The upper course is typified by what shaped valleys
V-shaped
The river usually occupies most of the narrow valley floor
32
The landforms of a V-Shaped valley are (5)
1. Uneven
2. Steep river bed
3. Rapids
4. Waterfalls
5. Large boulders
33
The processes of a V-Shaped valley are (3)
1. Vertical erosion
2. Large boulders transported (heavy rain), some suspension and solution
3. Large bedload deposited
34
The middle course or a river is typified by
the valley becoming wider (meandering). Flood plains are common
35
The landforms of a middle course are (3)
1. Small meanders
2. Small flood plains
3. Rapids
36
The processes of a middle course are (3)
1. Lateral erosion begins, mostly attrition, some hydraulic
2. Traction and suspended load increases. Some solution
3. Deposition on slip off slopes
37
The lower course of the river tends to carry
a large amount of sediment and large scale deposition occurs
38
The lower course of a river is typified by
it being very wide
39
The landforms of a lower course are (3)
1. Levees
2. Large meanders
3. Floodplains
40
The processes of a lower course are (3)
1. Small particles deposited, levees and slip off slopes formed
2. Small bed load, most in suspension
3. Erosion limited - lateral, outside of meanders
41
A meander is
a winding curve or bend in a river
42
River cliffs or bluffs form (where)
on the outside of meanders
43
Ox-bow lakes dry up to form
wetlands or other habitats
44
There are 5 stages in creating a meander
1. Pathways cut in straight river, flow swings from side to side
2. Undercutting and deposition - doesn't get wider
3. Continued erosion along outer bank - River cliff / bluff and point bars
4. Meanders continue to form through helicoidal flow
5. Erosion is greatest beyond the middle bend in the meander - migrate downstream over time.
45
Areas of much deeper water and lower current velocities
Pools
They provide species with deep-water protection and food owing to the organic matter that accumulates on the river bed. These are where to look for larger fish and otters and kingfishers seek out these areas.
46
Form where shallow water with high velocity flows over gravel or cobble material, creating a broken water surface
Riffles
home to animals that cling well and are favoured by fish as a feeding area, for shelter from predators because of the broken water surface, and by salmon, lamprey or trout as the sites of their egg nests (redds) due to the well-oxygenated water
47
A gently sloping deposit of sand, gravel and pebbles
Point bar
48
As the surface flow of water hits the outer bank it corkscrews, flows along the river bed then deposits eroded material on the inner bank
Helicoidal flow
49
Deposited load on the floodplain is known as
Alluvium
is rich in nutrients and leads to floodplains often being used for farming
50
Floodplains become wider when
there is a significant amount of meander migration as the width of the floodplain is determined by the sinuosity of the river and the amount of meander migration that takes place
51
A braided channel is one that is divided into smaller channels by temporary islands called
eyots
52
Braided channels tend to form in rivers that have a significant amount of (3)
1. sedimentary load
2. a steep profile
3. where discharge regularly fluctuates
53
Deltas are landforms formed at the mouth of a river where
the river meets a body of water with a lower velocity than the river (e.g. a lake or sea), resulting in the reduction in the river’s capacity to transport sediment.
54
Deltas are dynamic areas that change quickly due to the
erosion of unstable land during storm and flood events and the creation of new land
55
Clay sediment particles stick together, gain in mass and sink so increasing the deposition of sediment
flocculation
56
River habitat includes
aquatic and terrestrial areas
often changing over short distances and timescales owing to the dynamic nature of rivers
57
Planning river conservation and restoration actions is influenced by the
river biodiversity and its value in the river system
58
Rivers are subject to a wide range of pressures including (4)
1. point source and diffuse pollution
2. water abstraction
3. invasive plant and animal species
4. physical modification
59
Rivers cover what % of the earths surface?
less than 1%
less than 0.01% of surface water, freshwater environments
60
The communities of plants and animals associated with rivers are rich and varied, owing to the
wide variety of shelter, breeding and feeding opportunities
61
River habitats are underpinned by the underlying (2)
geology and climate
62
A patchwork of linked habitats called a
habitat mosaic
63
Habitats intimately connected to rivers include (5)
1. associated wetland areas
2. swamps and fens
3. bogs and mires
4. floodplain meadows
5. wet woodland
64
At a larger scale, a river reach can be defined as
a length of river that supports a characteristic assemblage of these habitat units
65
Succession in river-bank plant communities typically develops
scrub and woodland
66
Disturbance (e.g. due to floods) plays a vital role in structuring river communities and maintaining
high biodiversity
Disturbance can shift an ecosystem from one persistent state to another e.g. by restructuring an established vegetation community
67
Nutrient cycling is the reuse, transformation and movement of essential nutrients in the river system. The cycles of 3 nutrients are especially important
phosphorus, nitrogen and carbon
their relative scarcity in fresh waters and their influence on rates of algal growth
68
Nest digging by an individual salmon depending on the species and size, can disturb up to how much of the stream bed area, releasing sediment and nutrients that are deposited downstream
17 m2
69
Formed by vertical flow over bedrock, boulder or cobble river beds
Waterfalls
Spray creates wetland habitat favoured by organisms that need cool, damp conditions, such as mosses and lichens, as well as specialist beetle, stonefly and caddis species
70
Have a relatively steep gradient, with high water velocity creating torrential conditions. Large boulders provide shelter from high velocities for invertebrates and fish
Rapids and cascades
71
Areas of deep water with a smooth surface and intermediate flow velocities, often with gravel or sand river-beds
Glides
tend to have lower species richness and diversity than riffles, and are often occupied by aquatic plants
72
Wet areas linked to the main channel but with little or no flow during average weather conditions
Backwaters
shelter sites for adult fish, essential breeding habitat for dragonflies and important nursery areas for lampreys
73
Aquatic macrophyte (large plants) beds create complex habitats by forming physical structures that (3)
1. affect flow patterns
2. trap sediments
3. raise nutrient and oxygen levels
74
Adding ..... Improves water quality, stabilise sediments and increase the diversity of physical habitat types within the stream.
Tree roots and in-stream woody material
Accumulations of wood slows the water flow, creating pools and eddies where fish can rest, hide from predators and avoid direct sunlight. They also provide a surface for algae, fungi, bacteria, plants and insects to colonise
75
Is important for plants and invertebrates (notably ground beetles, spiders and craneflies). This habitat is important for conservation because it supports a diverse range of species, including several specialists as well as many that are rare and endangered.
Exposed sediment
76
An important source of food and shelter for aquatic species and support many terrestrial organisms, including bats and a wide range of bird species. Many of the plants and trees specialise in living in damp ground.
River-bank (riparian) vegetation
Communities range from mature woodland to species-rich grasslands
77
Provide which specialist habitat that are scarce in the wider landscape
River banks
Steep banks are used by otters for their holts and water voles for their burrows. Nesting sand martin colonies also use eroded river banks.
78
Favoured by wading birds, amphibians and dragonflies, and provide an important source of food for bats and reptiles
Floodplain water features
79
Floodplain water features are (6)
1. bogs
2. flushes
3. oxbow lakes
4. wet woodland
5. reedbeds
6. permanent wetlands
80
Evolved from hay pastures, a previously common feature of river valleys
Floodplain meadows
81
Floodplain meadows have declined in the last 50 years due to (3)
1. agricultural intensification
2. building development
3. lack of management
82
Floodplain meadows are important as (4)
1. flood storage areas
2. high nature conservation value - floral diversity
3. provide nectar for a range of insects
4. important early indicators of environmental change
83
A river or stream with a greater range of habitats generally supports
a greater diversity of organisms because it offers opportunities for different life stages and varied food and sheltering opportunities.
84
A primary goal of many river restoration projects is
Developing a wide range of habitats.
ideally achieved by allowing the river to develop naturally its full characteristic habitat mosaic
85
The region of sediment and porous space beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water
Hyporheic zone
86
Species that specialise in water habitats (8)
1. Daubenton's bat
2. Otter
3. Dipper
4. Emperor Dragonfly
5. Fresh Pearl Mussel
6. Atlantic Salmon
7. White-clawed crayfish
8. Caddis fly
87
Rivers themselves are hard to conserve because (2)
1. often the focus of so much human activity
2. often cross many countries
88
Rivers face direct impacts from man (modifications) such as (5)
1. dredging
2. damming
3. channelising
4. widening
5. weirs
where the river features themselves are altered to suit man’s needs such as flood prevention, navigation, fishing and water abstraction
89
Rivers face indirect impacts by man such as (3)
1. pollution
2. siltation from run-off from agriculture
3. excessive run-off from human settlements
90
Rivers are subject to a wide range of pressures including (4)
1. physical modification
2. water abstraction
3. point source and diffuse pollution
4. invasive plant and animal species
91
Restoration actions aim to restore rivers to
their natural state, restore biodiversity and the key ecosystem services that society depends on such as the provision of clean drinking water and the natural management of flood risk
92
The rivers of the UK and Republic of Ireland have a long history of alteration by humans for (6)
1. navigation
2. water and food supply
3. waste disposal
4. flood defence
5. settlement
6. power generation
93
The first human influences can be traced back to Neolithic times - how many years ago
6,000 years ago
when vegetation clearance for agriculture accelerated water runoff and sediment input
94
Based on River Habitat Survey (RHS) data in England and Wales combined, how much % of rivers have been physically modified through reshaping and reinforcement?
more than 50%
Scotland the figure is 17%
Northern Ireland more than 50% of lowland rivers
95
Channelisation involves (2)
1. the straightening, diversion and deepening of natural rivers
2. the creation of artificial channels
96
Channelisation aids (3)
1. navigation
2. improves drainage of agricultural land
3. reduces the frequency of flooding locally
97
Channelisation activities were accelerated in the last two centuries by mandates such as (2)
1. the Arterial Drainage Act (1945) in the Republic of Ireland
2. the Enclosure Acts of the mid-18th Century in England
98
Channelisation activity reached its peak during the mid-20th Century resulting in how many km of channelised river network in England and Wales?
8,504 km
99
Channelised rivers cannot sustain varied habitat for different invertebrate communities and juvenile fish because
they have uniform shapes and river-bed sediment that create a lack of flow variability.
100
Channelised rivers can exacerbate flooding downstream because (2)
1. Loss of temporary floodplain water storage,
2. combined with the straight nature of channels that accelerate flow.
Disconnect rivers from their floodplains which reduces the frequency of water and matter exchange with the floodplain (e.g. nutrient rich sediment).
101
Channelised rivers are maintained by
regular dredging
102
What bad effects does dredging have? (3)
1. immediate alteration of habitat
2. Increased fine sediment loads - lead to the downstream siltation of substrates that can clog the redds (egg nests) of salmon and trout.
3. deprive hyporheic macroinvertebrate communities of oxygen (e.g. white clawed crayfish)
103
Gravel extraction from rivers is still widely practised to
reduce local flood risk
104
What bad effects does gravel extraction have? (3)
1. alter the natural sizes of sediment and shape of a river
2. associated habitat can be slow to recover, depending on the flow and sediment supply regimes
3. extraction can create conditions that erode the river bed and banks
105
The practice of ‘de-snagging’ (removing wood from rivers) was used extensively in order to (4)
1. improve navigation
2. was thought to reduce flood risk
3. aid fish migration
4. assist drainage
106
Rivers without large wood tend to be (3)
1. wider
2. straighter
3. less biodiverse
Although accumulations of wood can increase local flood risk by redirecting water onto floodplains, this can reduce flood peaks downstream.
107
Weirs were built to create ponds to supply water for (3)
1. mills
2. industry
3. irrigation
Locks that are used to aid river navigation have a similar effect to weirs
108
Weirs significantly alter the natural character of rivers, especially in England and Wales where there are how many impoundments?
25,000
Although a proportion of the flow is able to pass over such structures, the natural movement of water and sediment are disrupted.
109
What are the impacts of weirs? (3)
1. Upstream of weirs, uniformly deep water submerges exposed bar and riverbank habitat - reduces the abundance of certain aquatic plant communities
2. create unnaturally ‘flat’ or stepped river profiles that lead to silt deposition and attendant problems such as heightened nutrient storage
3. the obstruction of species movement upstream and downstream
110
An estimated ?? km of Atlantic salmon spawning habitat is inaccessible due to weirs in Scotland?
5,400
111
Flow deflectors and rubble mats designed to
improve habitat for fish
112
Croys and groynes are no longer favoured measures because
they deflect the flow and alter the natural patterns of erosion and deposition which may degrade habitat
113
In some steeper rivers with coarse beds, boulders have been removed to construct deflectors leading to a loss of (3)
1. in-channel flow diversity
2. shelter
3. range of river-bed sediments
important for macroinvertebrate communities and fish
114
Artificial reinforcement of banks are made using (4)
1. boulders
2. timber
3. rubble
4. concrete
115
Artificial reinforcement of banks aim to (2)
1. reduce channel movement to protect land, settlements or infrastructure (e.g. bridges and roads)
2. to limit sediment input from eroding banks
116
What % of all RHS sites in lowland areas of the UK, have banks been reinforced?
63%
117
Negative effects of bank protection include (4)
1. restricting a river’s natural ability to erode and shift in response to floods
2. channel narrowing leading to increased water velocities that can in turn erode river beds
3. construction can lead to immediate loss of bankside habitats for example those used by water vole, sand martin, kingfisher and juvenile fish
4. a reduction in the channel and floodplain complexity needed to create diverse habitat
118
Flood embankments or levees built using earth or concrete are designed to
prevent rivers naturally spilling onto their adjacent floodplains
119
It is estimated that embankments reduced floodplain water storage and increased peak flows downstream by %
50-150%
120
Owing to vegetation clearance it is estimated that what % of the total bank length of rivers in England and Wales has no or very little bankside tree cover
25%
121
Species-rich floodplain meadows are also a very rare type of habitat with how many ha remaining in England?
1500
122
Accelerated runoff from urban development can lead to
river channel erosion and enlargement creating unnatural river morphology and habitat
123
The diversity of algal, invertebrate and fish communities can be adversely affected by (2)
1. degraded water quality and unnatural flow regimes when the area of impervious surfaces approaches 10% of the catchment area
2. Diffuse sediment input from areas used for agriculture, increases sediment yields leading to problems of river-bed siltation and altered morphology
124
Common invasive plants that inhabit river banks are (3)
1. Japanese Knotweed
2. Himalayan Balsam
3. Giant Hogweed
125
Common invasive plants that inhabit river banks cause physical alteration to the river by (4)
1. plants die in the winter
2. bare earth is exposed
3. more prone to erosion
4. excessive deposition of fine sediment in rivers
126
Invasive aquatic macrophytes are also highly damaging by
slowing flows and trapping sediment
127
Invasive aquatic plant species include (3)
1. Azolla
2. Lemna
3. Floating Pennywort
128
Invasive aquatic plant species cause problems by (4)
1. chokes waterways deterring angling
2. boating/navigation
3. obscuring light to the water below which affects the water life beneath it.
4. Animals can mistake it for solid ground and risk drowning
129
American signal crayfish cause problems by (2)
1. spreading crayfish plague
2. they can alter in-channel habitat by digging burrows that can undermine river banks, loosen substrate and in turn increase sediment loads downstream
The Chinese mitten crab is also highly disruptive and can destabilise river banks through burrowing
130
Rivers are vulnerable to climate change as they are
highly sensitive to altered temperature and precipitation regimes
131
Climate change will have what effects on rivers
more frequent extreme flows that could affect physical habitat stability as well as water quality.
These effects alter habitat, species abundance, composition and distribution and the connectivity between water bodies
132
How many dams are there in UK and Ireland?
596 dams in the UK
16 in the Republic of Ireland
133
The physical effects of Dam building are (3)
1. fragment rivers and disrupt the natural movement of water, sediment and biota
2. submerging upstream areas
3. disruption of the natural flow variability needed to trigger certain ecological behaviour - river health is severely degraded
134
A reduction in floods have what effects? (4)
1. unable to transport sediment and re-generate habitat
2. channel narrowing, reducing the habitat area available for spawning salmonids
3. stabilise mobile gravel bars and increase riparian vegetation cover, but with a lower species diversity than an unregulated river
4. reduction of sediment supply, that can lead to the development of ‘armoured’ river beds.
135
How many dams are on the planet?
2.8 million
136
Most of the remaining free-flowing rivers are confined to the less populated remote parts of the planet, including (3)
1. the Arctic
2. the Amazon
3. the Congo basins
137
The aim of river restoration is to
increase resilience and assist recovery by addressing hydrological, morphological, biological, chemical and societal issues within the catchment
138
River ecosystem Services (5)
1. Water supply
2. Flood water & carbon storage
3. Biodiversity
4. Recreation
5. Raw material and food supply
139
River ecosystem pressures (5)
1. Urbanisation
2. Point source pollution
3. Water abstraction
4. Diffuse pollution
5. Channelisation
140
Benfefits to people of restoring rivers are (4)
1. better water quality
2. improved biodiversity
3. water supply security
4. reductions in flood risk and pollution
141
The rehabilitation and restoration of floodplains and river wetlands… (6)
1. improves water quality
2. helps to retain and slowly release discharge from water bodies
3. facilitates groundwater recharge
4. seasonal aquatic habitats
5. corridors of native riparian forests
6. shaded riverine and terrestrial habitats
142
River wetlands can also help in maintaining the functioning of estuarine and delta ecosystems and creating
natural land features that act as storm buffers
143
NWRM
Natural Water Retention Measures
Retention areas are meant to receive the peak discharge of rivers and therefore to prevent flooding elsewhere
144
The Water Framework Directive and the Habitats Directive are major drivers for
restoration and sustainable water management in the UK
145
When planning river restoration we need to think on different scales: (4)
1. Catchment scale – looking at the whole river system and all the issues such as pollution, siltation, flooding, canalization that have occurred within the whole catchment of the river.
2. Reconnecting rivers with their floodplains – wetlands and floodplains are very rare habitats but they are also very valuable in preventing flooding upstream, slowing silt reaching the sea and allowing for rising sea levels due to climate change
3. Restoring river meanders – straightened rivers are more prone to breaking their banks and flooding and have a lack of habitats and biodiversity
4. In-stream enhancements – on a smaller scale things like woody debris, deflectors or bankside vegetation can be added. This might be all you can do in urban areas where major changes to the river cannot take place
146
Connectivity is the
continuous flow of water, organisms and energy through a watershed
When connected, rivers function like superhighways, linking land, freshwater and ocean habitats and transporting water and nutrients between them
147
Freshwater species populations have declined an average of how much % since 1970?
84%
fragmentation, pollution and over-extraction of water
148
Anadromous fish move between
rivers and the ocean (Salmon)
149
There are human consequences, too from river degradation and loss of biodiversity these are: (3)
1. Freshwater fisheries - barriers reduce the water quantity and flow of nutrients these fisheries require.
2. stagnation in larger reservoirs and the release of methane, a potent greenhouse gas
3. stealing the ground from beneath their communities feet. Dams prevent the downstream flow of the sediments that build and replenish deltas
150
River degradation and loss of biodiversity are caused by (4)
1. hundreds of thousands of dams around the world
2. overfishing
3. climate crisis
4. water pollution
151
There are various ways that pollutants end up in rivers including (5)
1. sewage plants
2. storm drains
3. agricultural run-off (silt, pesticides, herbicides, fertilisers, slurry)
4. industrial effluent
5. wastewater from urban development
152
There are many steps we can take to improve the water quality of our streams, such as (9)
1. Control farm contaminants – diffuse and direct
2. Plant trees to reduce land run-off
3. Remove or mitigate possible limiting factors, which will prevent natural recovery of the area e.g. point source discharges from factories etc
4. Manage stock more efficiently e.g. by fencing off streams to reduce direct water contamination
5. Take care when applying fertilisers and pesticides
6. Be aware of water table depth and avoid overusing water in dry seasons
7. Retire land from unsuitable uses or change land uses (e.g. pasture to forest)
8. Careful planning of urban growth - minimal impact on neighbouring waterways.
9. Continued control or removal of invasive species or pests
153
NFM
Natural Flood Management
154
WWNP
Working with Natural Processes
to reduce flood and coastal erosion risk involves implementing measures that help to protect, restore and emulate the natural functions of catchments, floodplains, rivers and the coast
155
Natural Flood Management aims to
reduce the maximum water volume of a flood (the peak flood flow) and/or delay the arrival of the flood peak downstream increasing the time available to prepare for floods.
156
Natural Flood Management uses 4 key, underlying physical mechanisms
1. Increasing storage: creating temporary storage e.g. reconnecting functioning floodplains and creating storage ponds
2. Increasing catchment and channel roughness: this ‘slows the flow’ e.g. planting trees and hedgerows, restoring meandering rivers and installing leaky dams
3. Increasing losses: this increases the amount of water that drains (infiltrates) into the ground or is lost back into the atmosphere via evapo-transpiration (e.g. agricultural practices to improve soil structure and installing sustainable urban drainage systems
4. De- synchronising peak flows from tributaries: Slowing down one tributary compared to another can significantly reduce flood peaks downstream.
157
SUDS
Sustainable Urban Drainage Systems
158
A successful natural stream restoration project requires following a multi-step process (4)
1. to define the objectives - flood control, improving water quality, improving recreation, improving habitat and biodiversity, or reducing bank erosion
2. assess current condition of the stream
3. determining the best course of action - A potential solution is to allow the stream to fix itself. This option may include doing nothing or removing stressors such as livestock or mowed stream banks
4. stream restoration design and construction involves reshaping the stream channel and floodplain, building in-stream structures, and protecting the bank
159
Observations to assess current condition of the stream (4)
1. noting any downcutting or widening
2. the amount, type, and condition of bank vegetation
3. changes in the watershed upstream
4. features downstream that are constricting flow
160
A re-vegetation plan for a river bank should include (3)
1. a list of native plants to be used
2. planting locations and timeline
3. a monitoring and maintenance strategy
161
In-stream structures that stabilize the stream slope to prevent erosion caused by downcutting and widening
Rock vanes
They also shift the flow of water away from the bank to the centre of the stream, where a scour pool is developed that dissipates energy and provides fish habitat
162
Several variations of rock vanes exist (3)
1. rock riffles (diagonally placed rocks that go less than halfway into the stream)
2. cross-vanes (extends from bank to bank)
3. J-hooks (rock structure built in the shape of a J)
163
A rootwad / Toe wood consists of (4)
1. a tree’s root mass and 10 to 15 feet of trunk
2. placed on the outside bend of a meander installed with the trunk portion entrenched in the stream bank with the root ball exposed to the stream.
3. Vegetation is added on top of the structure for erosion protection and habitat
4. used when stream bank sloping is not an option, typically on vertical banks
164
Benefits of large wood debris in a river include (10)
1. Stabilises river banks and beds.
2. Increases floodwater storage.
3. Provides habitats for fish.
4. Provides niche habitats – adds to the complexity of the river and the sediments creating new habitats.
5. Provide splits and hollows for invertebrates to hide
6. Supports up to 147 invertebrate species including dragonflies and mayflies
7. Provided cover for mammals like otters and perches for birds like dippers and kingfishers.
8. Improves water quality
9. Improves recolonisation of species and protects against drying out or freezing
10. Stores carbon in the wood itself as well as the sediments it traps
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Benefits of beaver dams (6)
1. Increase in riparian vegetation
2. Increase in channel aggradation
3. Increase in Dam persistance
4. Increase in fish habitat complexity - pools / gravels
5. Increase in floodplain reconnection
6. Decrease in stream temperature
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Paleochannels show the
historic location and form of the river
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An actively meandering channel will exhibit natural processes and features such as
erosion and deposition
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A passively meandering channel will show the form of a meandering river, but
none of the processes and forms of an active river
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The most suitable restoration option for a weir will depend on a number of factors these include (6)
1. the structural make-up of the weir
2. the condition of the river upstream and downstream
3. the aims of the catchment plan
4. the surrounding land use
5. funding
6. the presence of protected structures and habitats
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Hierarchy of actions to restore natural river processes high (best) to low (minimal action): (4)
1. Re-meander
2. Remove the weir
3. Bypass / modify the weir
4. Install a fish pass
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The degree to which a river can be free to adjust, or needs to be constrained, is heavily dependent on
site and catchment characteristics
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A weir is a barrier built-in river to (4)
1. change the depth of flow
2. alters the floor height of the river
3. used to control the velocity of flow during high discharge
4. also called a small-dam to store water in a small area
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The most suitable restoration option for a weir will depend on a number of factors: (7)
1. the structural make-up of the weir
2. the condition of the river upstream and downstream
3. the aims of the catchment plan
4. the surrounding land use
6. funding
7. the presence of protected structures and habitats
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Before selecting a bank protection technique, it is important to understand and identify the cause of the issue and type of bank erosion. This includes looking at (4)
1. the energy of the river
2. surrounding land use
3. bank cohesion
4. any structures or modifications that may be causing the problem
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Coir log is a natural fibre product designed to
provide soil stabilization and support along river banks, slopes, steams, hillsides, and other erosion prone areas
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Coir logs are versatile and can be used in many applications (9)
1. Drain protection to slow water velocity
2. Sediment control
3. Riverbanks and toe protection
4. Steep batters and sand dunes
5. Building sites
6. Wetland erosion
7. Coastal wave erosion
8. Sand bank regeneration
9. Soil amendment
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Willow spiling is a
traditional technique used for the prevention of erosion to river and stream banks.
Live willow rods are woven between live willow upright stakes which have been driven into the river bank. The willows then grow and their roots help slow flows and stabilise the banks.
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Natural flood management measures within a river catchment aim to: (2)
1. reduce the rate or amount of runoff; and/or
2. improve the ability of rivers and their floodplains to manage flood water
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Natural Flood Management techniques include: (6)
1. Breaching flood banks
2. Floodplain wetland mosaic
3. Floodplain spillways
4. Land profiling
5. Removing and setting back flood banks
6. Floodplain scrapes
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Instream construction during the spring (March 15 to July 31) and Autumn (September 15 to November 30) may need to be restricted to
minimize impacts to fish spawning
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Broadly the process of river restoration involves the following stages: (6)
1. Understanding the catchment
2. Pressure and impact assessment
3. Identify options
4. Set catchment objectives
5. Prioritise options
6. Who to involve/permissions
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The starting point for planning any river restoration project is to understand your catchment using (3)
1. River Habitat Survey
2. MoRPH
3. Fluvial Audit
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What is MoRPh?
a tool developed for citizen scientists to record information about local physical habitat conditions at a scale that complements biological monitoring
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What is the River Habitat Survey?
a methodology for recording habitat features for wildlife that was designed by the Environment Agency
is a systematic collection of data associated with the physical structure of watercourses. Data collection is based on a standard 500 m length of river channel. Map information is collected by doing a desk study for each site and includes grid reference (or latitude, longitude), altitude, slope, geology, height of source and distance from source
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What is a Fluvial Audit?
Fluvial Audit is a technique aimed at providing catchment wide geomorphological information to develop solutions to river management problems for a range of functions (e.g. water resources, flood risk management, fisheries). Fluvial Geomorphology is becoming an increasingly established discipline in managing river and floodplain form and behaviour.
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A river’s energy is a function of the discharge, channel slope and channel dimensions and is often expressed as
stream power
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A reference condition of a river is
the expected state of the river if modifications and impacts were not present. This is also known as the seminatural condition
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The main aspects that you need to consider for maping reference conditions are (6)
1. Natural environmental processes (e.g. hydrological, geomorphological, ecological)
2. Existing development, land ownership and future development plans
3. Functional use (e.g. conservation, amenity, flood risk management, angling)
4. Local site conditions (e.g. existing flora and fauna, river flows and levels, sediment movement, geotechnical)
5. Operational window of opportunity (e.g. weather, funding budget, fishing, bird-nesting)
6. Relevant policies, strategies, designations and regulation
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Pressure and Impact Assessment
A pressure is the cause of an issue (e.g. channel realignment), whilst an impact is the end result (e.g. poor habitats).
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SMART
Specific
Measurable
Attainable
Relevant
Time-Bound
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Making successive interventions to optimise or modify the restoration works is referred to as
adaptive management
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It is estimated that how much of global rivers are free-flowing?
around one-third
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The build-up of sediments and reduction in water flow can lead to
algal blooms and reductions in water quality
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In England and Wales, what % of freshwaters (excluding headwater streams, ditches, and ponds) fail to meet the minimum standards for Good ecological quality?
75%
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What % of our natural wetlands have we lost in Britain?
90%
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What ecosystem services do Beavers provide?
1. reduce flooding
2. lessen the impact of drought
3. engineer a mosaic of habitats
4. improve water quality
