2B Coasts fieldwork Flashcards
State the title of your physical geographical fieldwork enquiry
How do humans impact upon coastal processes at Walton-on-the-Naze on the Essex coast?
Name 3 risks associated with the enquiry and how you managed them
- One risk we potentially faced was muging. We managed this by staying in groups of at least 3 and having no valuables on show.
- Getting lost however had school contact number and maps of phone.
- Risk could have been heat stroke or hypothermia. We looked at the weather report in advance and made sure we had the appropriate equipment
What primary and secondary data collection techniques did you use?
Primary (Quantative)
- Groyne analysis
- Beach Profile
- Wave count
Primary (Qualitative)
- Field sketch
- Photogrpahs
Secondary
- Satelite images
- Geological maps
Describe the process of collecting groyne analysis data and its postives and negatives
Groyne analysis (primary & quantative) method:
- First choose a set height on a groyne to measure from
- Use a ,easuring tape to measyre the distance form the chsoen point on the groyned to the sand.
- Repeat down the groyne at even increments until you reach the shorline
- Then measure the height on the other side of the groynes at the same points you did on the first side.
- A lower measurement in cm would indicate higher sediment height. We would expect to find higher sediment height on the south-facing side of the groyne as this would show that sediment is moving from south to north, building up on the south-facing side of the groyne.
- Record results and plot a graph
Positives:
+ We used specialist equipment (tape measure) to ensure accuracy, and the same person measured each groyne
+ The equipment was easy and effective to use
+ We were accurate in measuring the same place on both sides since we chose an noticable object to measyure against such as a groyne pole.
Negatives:
- Could have been more accurate when measuring as tape measyre was not always vertical due to windy conditions anmd human error
- Could have collected more data for groynes and repeated on different groynes to have more reliable data
Describe the process of collecting beach profile data and its postives and negatives
A beach with a gentle slope shows that constructive waves are in action - swash is more powerful than backwash so sediment is deposited rather than carried away. A beach with a steep slope gradient shows that backwash is stronger than swash and that sediment is removed by destructive waves (a storm beach). Sediment deposition suggests that LSD should be occurring.
Beach profile (primary & quantative) method:
- First place a ranging pole as close to the water as you can safely go
- Then either use a measuring tape or take 5 strides up the beach to place the next ranging pole making sure the line between them is perpendicular to the shorline
- make sure both poles are submerged at the same depth in the sand and they are vertical
- Use the clinometre to calculate the angle from a set level on the fisrt pole to the same level on the next
- Take up the first pole and place on the same trajectory at the same distance back amd repeat until you have got to the end of the beach.
Positives:
+ Provided good overview of the gradient for the beach profile in the limited time we had
+ We used specialist equipment (clinometer, ranging poles) to ensure accuracy, and the same person took each measurement
+ We conducted x2 beach profiles and pooled our group results to get class averages to improve the reliability of our data
Negatives:
- The tide was coming in which meant that the beach profiles were of varying lengths
- Difficult to keep the distance the exact same every measurment
- Small changes in gradient were not picked up so smaller increments could be more accurate. Could have used strtified smapling
- Poles could not have been vertical and evenly in the ground due to differences in the resistnace of material.
Describe the process of collecting wave count data and its postives and negatives
Wave count (primary & quantative) method:
- Select a location with good visability of waves breaking on the shore
- Use a timer for 2.5 minutes and count the number of waes in that time and double it to get to five minutes. This was vecause it would have been diffiuclt to count for 5 minutes
- Then calculate the number of waves per minute to find out if they are destructive (>15 per minute) or contructive (<15 per minute)
Positives:
+ Efficient technique meat is was simple and quick to gather data
+ There was little equipment needed which minimises technical mishaps
Negatives:
- Waves were mot alwasy easily distringuishable from eachother leading to miscounts
- Human error due to countyiung over a longer period of time
- Measuring for half the time and doubling wasn’t completly accurate
Describe the process of drawing the field sketch and its postives and negatives
Field sketch (primary & qualitative) method:
- We drew an annotated field sketch of the cliffs at Walton-on-the-Naze, just north of the final groyne. We tried to include detail on rock type (Red Crag sand and London Clay), vegetation, and the Rip-Rap.
- A cliff sketch helped us to record the impact that the groynes were having in starving the beach of sediment. The beach would normally protect the cliffs from wave erosion. It also helped us to see if the rip-rap (built 2011) was protecting the cliffs from wave erosion.
Positives:
+ Completing a field sketch enabled us to collect contemporary evidence about the state of the cliffs in October 2024. Some secondary data might be out of date
Negatives:
- Field sketches are subjective (biased); they are my interpretation of what is going on, and might be different to someone else’s
What are the different sampling strategy for primary data collection methods?
Random:
- In random sampling each point or individual in the study area as an equal chance of being selected. This method is usually done by randomly generating number or coordinates to choose location or subjects, which helps to reduce bias
Pros:
- Objective and removes unbiased
Cons:
- Time consuming and can give nonlinear results
- May not should representative progression if sites are clumped together for example groyne analysis and beach profile
Systematic
- Systematic sampling involves points at regular, fixed interval (e.g. every 10 meters along a beach). This method ensures an even spread of data collection across the study area making it easier to cover a large area consistently.
Pros:
- Highly representative of progression - good for BP and G
- Easy to cover a large area consistently
- Not as unbiased as random as you choose the interval
Cons:
- May miss natural variation between the sample sites which satisfied
Stratified
- Stratified sampling is used when the study area or population is divided into distinct groups or “strata” (such as different coastal zones). Sampling is then conducted within each stratum, which ensures that each key area or characteristic is represented proportionally in the results.
Pros:
- Allows us to see the variations and can be more representative as different groups/categories are proportionally represented.
Cons:
- More biased as we choose the categories and intervals
- Time consuming - beach profile, beaches with varying profiles - bias
Opportunistic
- Opportunistic sampling means choosing sample points or individuals that readily available or easy to access. It’s often used when time or resources are limited, although it may introduce bias since the sample isn’t entirely representative of the whole study area
Pros:
- Easy and simple to collecting which could making it more time efficient if time constrained
- Useful in an environment where safety could be compromised - tide/rockfall
Cons:
- Not fully representative for all data
- Most biased as you are choosing when and where suits
Evaluating secondary data sources
Geological maps:
+ Offers a strong overview of a much wider area than we would have been able to survey during our allotted time to do fieldwork. Maps are easy to interpret with a key. Enable us to understand why we see the rates of erosion we do along the coastline as the geology directly affects the level of resistance due to wave action. It may need more protection that others due to their geology. Supports other data such as GIS maps showing rates of erosion pus our primary data methods of field sketch where we could see significant erosion and undercutting of the cliffs past crag walk.
- They do not show us the change and gradual erosion over time and only show a representation of one moment in time. Additionally the maps can be outdated in terms of the shape and areas of land still present although the geology itself will not have changed
Satellite images:
+ It is data that we couldn’t of collected on the day and it shows progression of erosion over a much larger scale of time which we couldn’t gather in one day. The GIS overlays on satellite images of previous cliff positions, enabled us to see the rates of erosion over time and additionally, with the 2012 line we could see the influence of Crag Walk on rates of erosion in front of the Naze Tower. USeful to understand the direct impact of human activity (rock armour) on cliff retreat and the immediate area protected. This helps support the primary data we collected to look at the impacts of human management on coastal processes
- The latest data point was only collected one year after the hard engineering had been completed and therefore the areas around hadn’t had an opportunity to erode much further so there is not much of a noticeable difference. Intervals of up to date are often quite large and therefore more recent changes are not available so we cannot currently see the most recent levels of erosion.
How did you present your data and why?
Beach Profile:
Line graph using a protractor to show the change in angle. This presented an accurate visual representation of the beach gradient, helping to visualise the gentle slope
Groyne Analysis:
Bi-polar bar chart. This enabled us to directly compare north-side of groyne figures to south-side of groyne figures and prove that the south facing side has more sediment and therefore sediment was moving north.
Field Sketch:
An annotated cliff-sketch enabled us to present contemporary data on the extent of the cliff retreat, the type of rock, the impact of the rip-rap protection etc.
Satellite images
2018 satellite image with cliff line from 2000 and 2012 annotated on top. By using different coloured lines to represent the 2000 and 2012 cliff lines we could clearly see how much retreat had occurred.
What were your overall conclusions
We can see that the role of groynes at WoN town have a significant impact on the process of longshore drift. This is evidence by our bi-polar graph to represent the groynes where the difference of deposition on each side range from 16 to 12 cm with and average of 13.4. This distance was consistently shorter on the south side supporting that the groynes were working effectively as there was more deposition build up on the south side compared to the north side. Furthermore because the southside consistently had a smaller drop at every point we measured we can say the groynes had a significant impact in preventing longshore drift.
Through the field sketch we can see that Crag Walk, the rock armour wall, led to a reduction in erosion of the cliffs in front of the Naze tower. Evidence of this was illustrated by the fact there is more vegetation growing behind the rock wall demonstrating the stable and safe ground that is therefore not being eroded due to rock armour. This is further supported by the GIS showing less erosion behind the rock armour in recent years
However, we could also see that, directly next to the end of Crag Walk, significant erosion of the unprotected cliffs was present. This is due to the energy of the waves being refracted around the rock armour and targeted at the cliffs immediately next to the rock armour.
We also collected data to measure the gradient of the beach to create a beach profile. The average gradient change was 3o this is a relatively shallow gradient change and there was limited variation in the change. This therefore suggests to us it was a constructive beach profile and suggest that the groynes were effective in building up the beach by reducing longshore drift and trapping sediment, causing it to be deposited.
