Lecture 1 Flashcards
What does a river remove from the catchment
Water and sediment
Name some variations in channel dimensions
Grain size, water quality, river width, flow, slope
How could a desert effect river morphology
Flashy flows, mostly runoff, periodic rain, greatly changing hydrograph
What is the name for when plants and animals change the natural system to suit themselves
Ecosystem engineers
Why can the hydrological cycle and hydrograph differ around the world
Soil, rainfall, evaporation ect
What is the main split between flows in the hydrological cycle
Underwater vs overland
What is common with groundwater flow
Water travels more slowly, more steady store
What does overland and underground run off change
The hydrograph
What is antecedent precipitation
If rainfall falls into already wet ground more water can be released
What effects surface runoff
Land use, vegetation, soil, basin shape, evlevation, slope topography
What concerning the catchment can effect hydrographs
Catchment shape
Why can steepness change channel hydrograph
Faster flow more flashy and peaked hydrographs
How can land use, namely urbanisation effect hydrographs
Runoff on hard surfaces can create peaky and flashy hydrographs
How can we predict what sort of flows a catchment will generate in the channel
Flow records, empirical approaches, physically based models
What are flow records
Gauging data from minimums and maximums, USA and uk large historical record
What are empirical approaches
Devised for when no gauges in the stream system, uses key characteristics to work out flow
What factors can we use in empirical approaches to model river flow
Catchment area, stream frequency, effective rainfall, soil type, slope, lake storage
What letter do we always use for discharge
Q
Name an empirical report used to predict river flow
Flood studies report
What factor is C in the flood studies report
Regional multiplier
What do empirical approaches give you
Estimates of what the empirical approach might be
What is the problem with empirical methods or flow records
Only says what is in the past or what has been
What are the two main groups of catchment based models
Spatial representation and process representation
What is a lumped model
Treating the catchment as one entity
What value is generated from a lumped model
A single value
What is a distributed model
Thinking about the catchment as a series of grid squares
What is the back box model
Process lumped model
What is a white box model
Process distributed model
What is a DTm
Digital terrain model
What are the attributes of a dtm
Slope, aspect. Altitude
What areas can you get data for that you couldn’t before
Lidar and satellite data
What are some key soil catchment variables
type and association
Derived characteristics
What are some key geology catchment variables
Type
Derived characteristics
What key catchment land use variables are there
Vegetation cover
Management practices
What key catchment artificial factors are there
Storm drains sewers
What are
Some important catchment inputs o
Precipitation, suspended/dissolved load, pollutants
What are some important river outputs
Discharge, water vapour, groundwater recharge/transfer, suspended dissolved load. Pollutants
Why do some models struggle with accuracy
Stores of water, can be very variable
Name a GIS based catchment model
Lisflood (Paul bates)
What are gis data layers used to represent
Catchment characteristics. Inputs and outputs, water stored in a system, flows within a system
What are calculations between layers in GIS based catchment models used to do
Represent relationships model processes predict response
What model is lisflood
Gis distributed model
What are the natural sources of solutes
Atmosphere, biosphere, rock and soil weathering (60%)
What are the controls on solute supply
Lithology, sedimentary rocks 5x that of crystalline
Time water is in contact with rocks, hydrology
What are the main solutes in the river system
Hydrogen carbonate, sulfate, calcium, silicon dioxide, they make up 80% of all solutes
What is suspended material
Small grains that are kept in the flow
Where does suspended sediment come from
Surface sources but also under water through flow
How much sediment is delivered to channel from catchment
Only 15%, most from t he channel itself
What is the sediment budget
The quantitative statement of the rates of sediment production transit and discharge
What are the three elements needed to construct a sediment budget
Transport processes, storage elements, identification of linkages amoungst transport processes
What is the equation for the sediment budget
O=I + AS
O = catchment sediment yield
I = sediment inputs
AS = change in sediment storage
What are the main hill slope processes release sediment
Gullying, mass movement, sheet wash, erosion
What has the majority of work been measuring sediment budgets
Small steams eg bed traps
How does Chernobyl help in dating soils
Isotopic dating of soils using radio active readings
Why is measuring sediment budgets difficult
Great variety of processes operating and wide areas where they occur
What is the USLE
Universal soil loss equation, empirically derived equation
What was the USLE designed for
Designed for just small plots
What is A in the USLE
Soil loss per unit area
Name an example of a numerical flood method
CAESAR coulthard et al
What does coulthards model show
More human contact and deforestation linked with more sediment into the river streams
What can sediment aggregation and degradation occur in response to
Increase or decrease in supply, water division or climate change, channel straightening, land use change, floods or other sudden inputs
How can land use changes impact the sediment budgets
Agriculture intensification or abandonment, commercial forestry, urbanisation, mining
Which industry presents a big challenge to sediment budgets
Forestry
How do you start forestry cycles
Removing natural cover and improving the drainage, much flashier regime, more sediment in the system
What happens at the end of the forresty cycle
Cut down trees lead to lots of run off and added sediment in the system
If the river shows and equilibrium what can be said about the river system
It is in balance
what controls catchment runoff
regional climate, topography, geology, soils, vegetation and land use
Was is the nature of sediment delivery
Normally highly pulsed
When can sediment enter the river directly
When river banks erode
Where does the bulk of a rivers sediment come from
Headwaters
what performs the drainage of earths land
stream networks
what are stream reaches embedded into
stream networks
what are network patterns
the spatial arrangement of river channels in the landscape
what is the pattern of most drainage systems
dendritic
what is the angle of stream junctions downstream
below 90 degrees
who created stream order
strahler
which channel shape is treelike, with no preferred channel orientation, acute intersection angles
dendritic
what can channel junctions be termed
nodes
what is drainage basin magnitude
the amount of exterior links a channel contains
what is the londitudinal profile of a stream
plot of the elevation versus length
what is the normal shape of a stream longitudinal profile
concave
what is a streams base level
the elevation of the stream near the river mouth
what is a distributary channel
one that slpits of into multiple channels, like deltas or alluvial fans
what is the drainage density of a stream system
total length of streams, divided by the area
what are exorheic systems
ones that drain into the sea//ocean
what are endorheic systems
rivers drain into the inland seas, or wet lands, which is then evaporated
what did Vorosmarty use to find out basin sizes and river stream orders
STN-30p
compared with UNESCO sizes, how much did the STN-30p differ in size
=13%
how many true first order streams are there worldwide
14,500,000
what are the only 2 6th order (true 11th) streams
Amazon and Lena
what is the average length of a 1st order stream
0.78km
how many second order streams are there
4,150,000
what percentage of global rivers are exorhiec
87%
What are the 4 causes of convexities in river longitudinal profile
Local rock formations, coarse sediment, tectonic uplift, drop in base level
What is a knick point
Pronounced steepening convexities
What happens to sediment size as we go doenstream
It decreases
What 2 processes reduce grain size over distance
Grain breakdown by abrasion, selective transport of finer sediments
what is the difference with Anabranching reaches compared with braided rivers
anabranching rivers are fixed in position
what is the shape of a normal cross section shape
concave but asymetrical
What was the main control on sediment concentration in the Yorkshire stream tested by naden and cooper
Land cover and use
What is a rill
A shallow channel cut into the soil by the erosive action of flowing water
What is the larger stage up from rills
Gullies
How are rills initiated
When water erodes topsoil on hillsides
What is over come to lead to rill creation
Soil shear stress is over come by water shear stress
