physical fieldwork Flashcards
What is you physical fieldwork enquiry question?
enquiry question:
What physical factors influence flood risk in Church Stretton?
What is the aim of your physical fieldwork enquiry?
aim:
To investigate the physical factors which influence flood risk for people and property in Church Stretton.
What are your three sub-hypotheses?
hypotheses:
1) river discharge increases as you move downstream, causing greater flood risk to Church Stretton
2) river velocity increases as you move downstream, causing greater flood risk to Church Stretton
3) human activity has altered the river valley to increase flood risk in Church Stretton
Explain the three theories your physical fieldwork enquiry was based upon.
theories:
1) long profile of a river
- upper course - v-shaped, narrow and lots of sediment and waterfalls and gorges
- middle course - gentle sloping, wider and deeper, more suspended sediment, meanders and slip off slopes
- lower course - gentle sloping with floodplain, very wide and deep, flood plains
2) the bradshaw model (shown by triangles) as you go downstream (towards lower course) - discharge increases - channel width increases - channel depth increases - velocity increases - load quantity increases - particle size decreases - bed roughness decreases - gradient of valley decreases
3) river management
- hard and soft engineering are used to reduce flood risk by managing rivers
- hard engineering - artificial structures to control rivers
- soft engineering - sustainable and natural approach to controlling rivers
Why was Carding Mill Valley at Church Stretton chosen?
why this location?
- easy to access
- area has been pedestrianised
- the three chosen sites were safe (water wasn’t too fast and the river wasn’t too deep)
- visited in summer to reduce risk of high water flow or rainfall
- there was enough variation between the sites to show changes in width, depth and velocity
What were the risks and how did you reduce them?
risk assessment:
drowning - went to shallower parts, looked at forecast before, first aid kit and phones
fast flowing water - choose slow and shallow parts, wear wellies
Weil’s disease (caused by rat urine) - don’t put head in river, wash hands, plasters on open cuts, if water is swallowed then have bottled water on hand and seek medical assistance
falls and cuts - suitable footwear, not too deep parts of river, avoid vegetation (trip)
getting lost - walk in groups, maps, phones
traffic accidents - walked single file together, stay on paths
What is stratified sampling?
Stratified sampling is separating data into sections.
What is systematic sampling?
Systematic sampling means working to a system to collect data.
Why was systematic sampling used to choose the three sites?
We used systematic sampling to select the three sites to allow a good coverage of the river to be represented. Also, avoids risk of deeper and faster areas.
What were your four primary sources of data, how did you carry them out and why?
primary data:
1) measuring cross section of river
- use tape measure to measure width
- use metre rule to measure depth
- do at 10 cm intervals
- done to see if discharge increases, if supports Bradshaw model
2) measuring velocity of river
- put ranging pole in water, measure 10 cm with measuring tape and place other ranging pole
- put cork in water, start timer and stop when gets to other ranging pole
- repeat at other parts of river for average
- done to see if speed increases, if supports Bradshaw model
3) land use survey
- walk along river, observe and record uses of land at each stage
- investigate how humans have affected flood risk
4) field sketches
- draw sketch by drawing major lines as guidelines and then adding details and annotations. do at each site
- to discover the changing characteristics of the sites
What were your four secondary sources of data and why did you use them?
secondary data:
1) environment agency flood risk map
- locate specific areas at risk by separating them into three zones, it is up to date, visually clear
2) river gauge data
- gives data on water level at river, can compare to the past
3) land use map (bing)
- includes scale, visually clear
4) uk meteorological data
- gives conditions of river, temperature, wind and precipitation, provides weather warnings
Describe two ways in which you presented your data.
data presentation:
1) cross sectional graph
- label depth and width on a graph to show cross section
2) land use map
- outline where there are different types of land use and colour in different colours
- add annotations to show what influences the land has
Give the width, mean depth, mean velocity and mean discharge at each site.
discharge = cross section x velocity
site 1 width - 0.8 m depth - 0.12 m velocity - 0.22 m/s discharge - 0.02 metres cubed/s
site 2 width - 1.3 m depth - 0.37 m velocity - 0.39 m/s discharge - 0.19 metres cubed/s
site 3 width - 2.1 m depth - 0.51 m velocity - 0.52 m/s discharge - 0.57 metres cubed/s
What do your results show in relation to your hypotheses and why?
My results show that the river widened and deepened as you went downstream. The discharge also increased as more tributaries (small streams) join, bringing more water, increasing the energy of the river so it erodes, deepens and widens. Therefore, it has more capacity, increasing the likelihood of flood risk. This proves that the Bradshaw model is correct. I can accept my first hypothesis.
My results also show that the velocity of the river increases as you go downstream. This is because more discharge creates more energy for the river to erode, transport and deposit material, and friction will reduce the size of sediment, proving the Bradshaw model correct. As it travels quicker, there is more chance of flash flooding. I can accept my second hypothesis.
The car parks and managed pathways increase surface run off, the reservoir and stone traps limit the flow of water, decreasing velocity. Removal of hedgerows and vegetation increase surface run off, as do the impermeable surfaces (houses, roads). I can accept my third hypothesis. However, humans have also helped; flood plain zoning near site 3.
What problems did you encounter and how would they affect your results?
problems:
- river cross section - only visited once, wet so not representative, only three sites, human error recording data
- river velocity - weather, human error, equipment problems
- land use survey - only three sites, human error, incorrect identification, changes
