River Chess Fieldwork

River Chess background information

The source is an aquifier, in chesham.

it does not have a mouth it is is a tributay of the river colne which it joins at rickmansworth. river colne is a tributary of the river thames.

drainage basin covers an area of 105 sq, km and there is an average rainfall of 768mm/year.

the main settlements are cheshman chorelywood and rickmansworth.

the chess is 18km in length falls 60km and is a typical chalk stream.

the river has one trivutary the chalk stream which is 1.7 km in length.

what are the specific sites we went to

upper course, chesham moor and one in the middle course, scotsbridge hill to allow a comparison.

advantages of choosing this river to study

river is 18km long, possible to visit the upper and lower course in one day. important becuase it means we will be able to measure the channel characteristics with the conditions being the same making our results from the two sites comparable.

close enough to school to visit in one day. access suitable sites safely and none on private land

teachers have been before and have data from previous years which we could use as secondary data to check against. FSC staff use these sites regularly so are aware of the risks and can ensure that we carry out fieldwork in safe conditions.

how does sediment load and velocity change along the river chess’ source?

the river chess has increased sediment load down the river and the velocity increases downstream.

How does secondary data help with understanding our river.

The BGS Geology map showed us that the underlying bedrock of the river chess is chalk.

this is permeable and highly poroous and thus water infiltrates into the ground/

usefu; in helping us understand the kind of hydrograph that will be associated with river chess (subdued0 and to begin to understand the flood risk along the length of the river.

GIS Environmental agency flood risk maps showed that chesham moor was in flood risk zone 3 whereas scotsbridge mill was in flood risk zone 1.

Land use and flood risk for Chesham moor

built up area, some open space, not much forestry around the river, steep sloves on either side of the river, river channel looks narrow and shallow.

built up areas have impermeable surfaces so more water flows as surface runoff reducing lag time and increasing peak discharge. not much open space and little forestry = less interception and use of water = short lag time and higher peak discharge.

steep slopes = more surface runnoff = shorter lag time and higher peak discharge.

narrow shallow channel means less river capacity so more likely to overflow and flood.

on the map: close contours = steep relief, less chance for inflitration = more surface runoff, flashy hydrograph.

if it does flood, the impact on people and property will be greater.

evidence of flood management in photos to stop erosion of the bank.

land use and flood risk for scotsbridge mill

less built up,

more open space and forestry,

slopes not as steep,

channel = wider and deeper

more permeable surfaces means rainfall can infiltrate into the soil and rock reducing suface runoff increasing lag time and lowering peak discharge,

more open space and forestry will mean more interception and use of rainfall increasing lag time and reducing peak discharge.

wider depper channel means the irver has more capacity to hold water so less likely to flood.

on the map: vegetation causes interception and less water reaches river = subdued hydrograph.

less built up so more infiltration, flooding less likely. less impact of people.

in photo = evidence of embankment to reduce flood risk.

River Chess Fieldwork Hypothesis

Width and depth will increase with depth downstream.

Flood risk will be affected by both drainage basin characteristics and channel characteristics.

River Chess Risk assessment

weather - hypothermia, overheating dehydration, sunburn, appropriate clothing and foot wear and food and drink. need to watch for changes in weather throughout the day.

traffic - green cross code

instructions - listen

slipping/tripping, appropiate foowear, being vigilant, being in threes,

weil’s disease, infection through open wounds or eating with hands that have not been washed, cover all cuts and use hand sanistiser before eating.

getting wet - water may come over wellies, bring socks and trousers and shoes.

river chess types of data

primary data, river width and depth average velocity, bedload length

qualitative, bedload shape, annotated photographs, flood risk survey.

secondary data, flood risk maps from environment agency geology map from bgs.

Chesham Moor Data

width - 4.9m

depth 0.3m

cross sectional area, 1.5m²

average float velocity, 0.33

average hydroprop velocity, 0.34

discharge 0.5 m³/s

average pebble length 44.9mm

avergae pebble roundness mode 1.4

Chesham Moor Flood risk

social impact score = 2

economic impact score = 2

environmental impact score 2

total impact score = 6

Scotsbridge Mill data

width = 10.12m

average depth 0.32m

cross sectional area = 3.3m

average float velocity = 0.77m/s

average hydroprop velocity = 0.77

discharge = 1.6m³/s

average pebble length = 28.5mm

average pebble roundness mode = 3

Scotsbridge Mill flood data

social impact = 1

economic impact = 1

environmental impact = 2

total impact score = 4

Explain how your fieldwork enquiry improved your understanding of an area of geography

Width and depth will increase with depth downstream.

Flood risk will be affected by both drainage basin characteristics and channel characteristics.

we concluded that our downstream site sctosbridge mill had greater width of 10.12m and an average depth of 3.2 meters, supporting our hypothesis. We concluded that chesham moor, our upstream site had increased flood risk as steep slopes = more surface runnoff = shorter lag time and higher peak discharge.

narrow shallow channel means less river capacity so more likely to overflow and flood.

in your physical environment fieldwork you should have used a geology map. explain one way this was helpful in your investigation

using the GIS geology map helped me to select sites at which to collect data. because it showed where rock types of different levels of vulnerability to erosion are situated along the coast.

explain one way using a geology map supported your investigation

BGS Map was used to identify the underlying bedrock of the river chess’ drainage basin. it identified that the bedrock is chalk which is a permeable and highly porous rock and thus water infiltrates into the ground. this is useful in helping us understand the kind of hydrograph that will be associated with the river chess and to begin to understand the flood risk along the length of the river.

explain why you chose your fieldwork data collection sites.

river is 18km long, possible to visit the upper and lower course in one day. important becuase it means we will be able to measure the channel characteristics with the conditions being the same making our results from the two sites comparable.

using the GIS geology map helped me to select sites at which to collect data. because it showed that the river bed is made of chalk which is highly porous and permeable. this is interesting as it allows us to assess the flood risk due to this.

explain one way that the use of maps was helpful in your investigation

using a flood map helped me to select sites at which to collect data becuase it showed where different flood defence strategies were used along the river.

explain why particular aims or questions were developed

we looked at changes in discharge downstream since the map evidence indicated there would be a big different in a short distance. this would allow a valid set of data to be collected and compared to other sites.

we decided to investigate changes in stone size and shape as there was some secondary data about this, whcih allowed us to compare our results to the publish data.

describe one of the quantitative data collection techniques that you used

we measured the river’s width in our upstream and downstream site. we used a tape measure at the widest point. to confirm our hypothesis that the river’s width increases downstream.

for your chosen river location, explain two ways that you collected quantitative fieldwork data.

data on stream width was measured by holding a tape measure at the widest point.

avaerge size of bedload was using random sampling techniques, 10 samples taken at each site.

describe one source of qualitative data that the student could collect as part of an investigation into factors affecting flood risk

annotated photographs/field sketches could have been used, to show which land use change have occurred near the river, such s deforestation, building of roads, house.s

explain one reason why the method you used to measure stream depth was appropriate for the task

i used a metre ruler and tape measure. = appropriate becuase the stream was not deep under 30cm allowing for safe and accurate measurment.

explain how one of your primary data collection techniques was appropriate to the task

i analysed pebble size at differentpoints along the river to find out how it changed due to attrition. I took a random sample of 10 pebbles at every site to make sure that the data collected was reliable. the data showed that pebble size decreased as the distance from the source of the river increases so i was able to asnwer my question

one possible cource of error when measuring stream depth

i used a meter ruler, if the stream bed had been sand, the ruler might have sunk into itand this could have introduced errors

explain how one of your primary data collection helped you to answer the question

i analysed pebble size at differentpoints along the river to find out how it changed due to attrition. i took a random sample of 10 pebbles at every site to make sure thatthe ata collected was reliable, this data showed that pebble size decreased as the distance from the source of the river increased.

explain one way in which you attempted to make your data collection reliable.

when measuring the stone shape using the power’s roundness scale a sample of 10 pebbles at each site was selected. the largest and smallest pebble is removed from the samples to remove extreme results the collection of 10 pebbles at each site gave a large data set in order to calculate a vetter mean = more reliable.

one way a secondary data source you used supported your investigation

bgs geology mapindentified underlying bedrock of the chess’s drainage basin. that it was chalk and highly permeableand water infilrates into the ground. useful in helping us understand the kind of hydrograph that will be associated with the river chess and to begin to understand the flood risk along the lenght of the river.

one possible source of error with method you used to measure river channel depth

tape measure and ruler. tape needed to be stretched across the river and ruleer had to be vertical. sagging tape or angles ruler could produce innacurate results.

if river bed not visible, end of metre ruler might be touching other things like boulders, giving a shallower reading opposed to actual depth.

evaluate the success of the primary data collection methods used in your investigation

the measurement for width and depth at each site = v effective as we could calculate a mean. the random sampling of pebbles at each site, removing extremetites and calculating a mean showed clear difference in sediment size upstream and downstream due to attrition.

the hydroprop was difficult to use as we had to ensure humans wading through the water didn’t impact the velocity. even when calucating a mean we did not remove any outliers so a faster veocity must have been recorded.

state two ways in which you managed the risks assoicaied with your fieldwork.

walked in single file, facing oncoming traffic. - reduces road traffic accident risk

wore appropriate clothing for the weather.

explain 1 way you used GIS in your own river processes and pressure investigation

i used the BGS website to find out about the geology of the river' chess’ drainage basin. useful as it provided background info to help explain the possible flood risk to fieldwork locations.

one technique that you used to present your river sediment

dispersion diagram, to show the variation in bedload size along the iver. allowed the changing pattern of stone size to be easily interpreted with changing distance from source

two strengths of one of the data presentation techniques you used

3 cross profil diagram, avisual indicator and trend between river easily seen

dispersion graph to present the data on sediment roundness and sedment size, the strngth of this techniueq - shows spread o data in the sample visualy well and easy to see any clusters in data. used to compare more than 1 set of data. = 3 sites could be plotted.

EQ survey results could have been presented as a radar graph, advantage

display data on seveal diff variables, good way to compare the characteristics of different areas

one limitation of your data presentation methods

3 cross profile = line graph which downs the width and depth of river channel. weakness = if scale not chosen carefully then horizontal or vertical exaggeration can orrcur. vertical can make river look too deep.

evaluate methods you chose to analyse and present primary fieldwork data collected.

putting raw data into a spreadsheet then working out averages = easy to do.

3 cross profile, type of line graph which downs the width and depth of the river channel. very visual graph so its easy to see how channel width and depth change dwonstream. easy to see visually how much of the water is not in contact wit h the bed and banks.

3 cross profile = line graph which downs the width and depth of river channel. weakness = if scale not chosen carefully then horizontal or vertical exaggeration can orrcur. vertical can make river look too deep.

explain 2 ways in which you analysed your river sediment data

median was used to determine a measure of centraility for stone size data. calculated an IQR to understand more about the spread of the data.

explain why statistical techniques used to analyse were appropriate

calculated IQR w sediment size, in order to extablish more about dataspread. data divided into 4 equal groups w median at the centre of 2 groups, appropriate as we had big sample of pebbles and showed variation well.

explain how case studies or theories helped you to analyse your results.

The theory I used to invesigate changes in river channel characteristics with distance downstream was the

Bradshaw model (1). This model suggests that with distance downstream, channel characteristics such as

width, depth, cross-sectional area, velocity and bedload roundness increase, whilst bedload size decreases

(1). So in analysing my results I was aware of what results I should be getting in relation to geographical

theory and therefore I could conclude whether the changes were as expected (1) and whether my results

proved or disproved the Bradshaw model theory (1).

Evaluate the methods you chose to

analyse and present the primary

fieldwork data that you collected. [8]

bradshaw model - 1). So in analysing my results I was aware of what results I should be getting in relation to geographical

theory and therefore I could conclude whether the changes were as expected (1) and whether my results

proved or disproved the Bradshaw model theory (1).

putting raw data into a spreadsheet then working out averages = easy to do.

3 cross profile, type of line graph which downs the width and depth of the river channel. very visual graph so its easy to see how channel width and depth change dwonstream. easy to see visually how much of the water is not in contact wit h the bed and banks.

3 cross profile = line graph which downs the width and depth of river channel. weakness = if scale not chosen carefully then horizontal or vertical exaggeration can orrcur. vertical can make river look too deep.

explain how fieldwork data collection you completed supported your conclusions

the measurement for width and depth at each site = v effective as we could calculate a mean. the random sampling of pebbles at each site, removing extremetites and calculating a mean showed clear difference in sediment size upstream and downstream due to attrition. supported our river width and pebble size hypothesis

explain how data collection techniques used in one of your enquiries could be improved to make the sample more reliable

Sediment roundness was judged using the Power’s Scale of Roundness which was

very subjective as it is based on judgements related to how well the selected pebble matches to the shape

characteristics on the scale. (1) This data collection technique could be improved by only having one person

deciding on roundness category at each site (1). Although this technique is subjective it will be more

consistent (1) as the changes observed at each site will be repeatable as the person making the judgements

will give similar judgements if they use the technique again. (1)

one possible source of error in one of your data collection techniques that you used in your physical environment feedback

Measuring bedload roundness and size was conducted by randomly selecting 12 pebbles from the river

bed at each site. However, we might not have been as random in our selection as we intended as we

were drawn to picking up the larger pebbles (1) this means that we may not have a truly representative

and reliable sample from each site. (1)

explain one factor about your own primary data which could have affected your results

River sediment data was collected using random sampling procedure, but this meant that larger samples

were more readily favoured (smaller ones being ignored or too small to measure) (1). As a result, the

median and mean values were likely too high and might be unreliable (1).

reliability of river fieldwork conditions

River sediment data was collected using random sampling procedure, but this meant that larger samples

were more readily favoured (smaller ones being ignored or too small to measure) (1). As a result, the

median and mean values were likely too high and might be unreliable (1).

the measurement for width and depth at each site = v effective as we could calculate a mean. the random sampling of pebbles at each site, removing extremetites and calculating a mean showed clear difference in sediment size upstream and downstream due to attrition. supported our river width and pebble size hypothesis