mudeford spit (physical) Flashcards
(27 cards)
what is a hypothesis?
An idea or prediction which has not yet been proven
what is the hypothesis of the project?
‘_______ at __________________ are having an effect on __________________.’
Groynes at Mudeford Spit are having an effect on longshore drift.
why is our hypothesis for this project important?
It’s important to know the groynes on Mudeford Spit are effective and working correctly because:
- dysfunctional groynes hinder recreational opportunities (beach huts)
- the saltmarsh behind is a site of special scientific interest, with rare plants and animals. if the groynes ceased to work, the spit would be eroded and the saltmarsh would disappear
- tourism from the café and ferry (on the spit) provide an income and jobs
- Mudeford Spit protects the Christchurch Harbour behind
why is Mudeford Spit an ideal place to carry out the project?
- relatively close to school
- safe, sheltered location
- wide, flat beach which is safe to walk along and collect data
- not overly busy with members of the public
- many groynes, giving us many options to investigate
what risk did the sea pose, and how was it managed?
- large destructive waves could sweep students into the sea
- stayed well back from the water (2 metres), especially when completing the beach width surveys
what risk did the beach pose, and how was it managed?
- risk of tripping or stumbling
- didn’t run on the beach, watched where we stepped
what is the difference between primary and secondary data?
primary data: data you’ve collected yourself, rather than from somewhere else (e.g. questionnaire, taking a photo, survey)
secondary data: date or information collected from someone else (e.g. historical maps, researching using the internet, satellite imagery and maps, past data)
describe the data and how it was collected:
- primary data. first 5 groynes sampled, 2 measurements of each (10 data points in total)
- standing at the back of the south-west side of the groyne and walking in a straight line parallel to it, I counted the normal-sized paces as I walked. stopped 1 metre from the sea, repeated this on the North-East side of the groyne
how did the data collected help answer the hypothesis?
knowing the beach width (number of steps needed) beside each groyne will tell us if they’re stopping longshore drift
- if a groyne stops sediment from moving along, a wider beach should occur on one of the sides: the south-west side
what sampling method was used by the students?
systematic sampling
- quick and easy method, where a regular sample is taken
what sampling method was used by the staff alongside systematic sampling?
stratified sampling
- people or places are chosen deliberately according to the topic being investigated
what were the positives and negatives of the systematic sampling method?
positives:
- simple to do
- sample is evenly distributed (e.g. first 5 groynes on the spit)
negatives:
- may not be possible to sample every groyne in the desired order, due to a hazard or other issue
- may not cover all groynes on the spit (are larger sample size is optimal)
what were the strengths and weaknesses of the data collection method (beach width measuring)?
strengths:
- easy to do, nearly anyone could do it
- quick to collect the data, not time-consuming
- no equipment required
weaknesses:
- walking in a straight line wasn’t always possible due to the beach conditions (impacting accuracy of data)
- paces aren’t a known unit of measurement, not accurate
- your paces are unique and can’t be compared to another student’s data
evaluate the sample size:
- 5 groynes, each with 2 measurements. 10 data points in total
- adequate sample size, as there are 12 groynes in total, so 42% of all groynes were sampled
- sample size could be increased by sampling more groynes
what were the mean, median, mode, and range values for the data collected?
south-west:
- mean: 47.8
- mode: n/a
- median: 47
- range: 9
north-east:
- mean: 32.6
- mode: 31
- median: 31
- range: 6
which graph types could have been used to display the data?
- bar chart
- divided bar chart
what are the strengths and weaknesses of the data presentation method (compound bar chart)?
strengths:
- clearly able to show results
- allows you to see patterns and anomalies
- helps to answer hypothesis, bars kind of look like the width of a beach
- shows data AND locations
weaknesses:
- using too many bars in one chart looks cluttered
- bar charts often require more explanation to show what the data means as they’re often too simple
- can be easily manipulated to give a false impression, e.g. the axis can be elongated to make the bars look longer
what does the graph show about the beach widths along Mudeford Spit?
- moving along the spit, it’s obvious the south-west sides have wider beaches than the north-west sides
- there’s a clear, repeating pattern of a wide beach reading (south-west), short beach reading (north-east), repeat
- groyne 2 is above the mean for other groynes
- no massive anomalies
what does the data in the graph tell one about the hypothesis?
- longshore drift is moving sand and sediment along the beach from the south-west to the north-east
- the groynes are clearly working, as the beach is wider on the south-west side of the groyne, therefore the groyne is stopping the movement of sand along the spit and it’s building up against the groyne instead
- helps answer the hypothesis that the groynes are having an effect on longshore drift
what anomalies could there be in the project?
- were all groynes built same length?
- did we walk at the same speed on each beach width? (could alter pace length)
- were the waves coming in or out as you ended your paces on each beach width?
what is your conclusion: do you accept or reject the hypothesis?
- accept the hypothesis, as we’ve observed that the groynes are working
- the data shows that the south-west side of each groyne is wider, therefore the groynes are effective, as they are halting the movement of sediment along the spit
- 100% of my classmates’ data backs up this idea
- clear, repeating pattern of a wide beach reading, then a shorter, beach reading, then repeat
what is another method that could have been used to test the hypothesis?
- systematic: measure the height difference on either side of the groynes as longshore drift builds up both beach width and beach height
- use 2 metre high ranging poles and a tape measure on the rock groynes to give a fairly accurate measurement of the height difference by measuring the drop height different between the two poles
what secondary data sources would have been useful to our study?
- past satellite images/historical photos: can observe whether the beach width has changed over time
- previous years’ data: can compare the obvious pattern from my graph with theirs
how could the sampling method and sample size have affected the accuracy and reliability of our results?
sampling method: only did the first 5 groynes of the spit. it only takes one of the data points to be inaccurate to throw off the entire investigation, as there’s such a small sample size (e.g. faulty groyne, people in the way)
sample size: one of the groynes may have had an issue - a larger sample size means the inevitable errors could be minimised
