Physical fieldwork: Enquiry Question
“What impacts do different methods of coastal management have on the coastal processes and communities in Swanage Bay?”
Context of the study
- Rates of erosion were high at Swanage Bay, 80% chance Swanage’s sea wall would collapse
- Many projected losses (lives & infrastructure)
- Since 1985 Swanage Beach has narrowed by 20m
So, in 2005, 19 timber groynes built, beach replenished w 160,00 metric tons of sand, hoping to stabilise erosion
2 different management plans on Swanage Bay
- Retreat the line
- Hold the line - do maximum (groynes & beach replenishment)
We will be able to find out which is most effective & provides most protection to beach
Test 1: What impacts have coastal management techniques had on coastal processes? BEACH PROFILES (Quantitative data)
- Systematic sampling: One location in ‘retreat the line’ management area, another in the ‘hold the line’ management area
- Method:
1. place a ranging pole at the sea & identify where the beach changed angle, place a ranging pole here.
2. Measure the distance between each ranging pole in metres.
3. Measure the angle between the ranging pole by using a clinometer to look from the top of the red line to the red line on the other ranging pole in degrees.
4. Now look for the next change in gradient up the beach
5. repeat the steps above till you reach the cliff.
Test 2: What impacts have coastal management techniques had on sediment characteristics SEDIMENT SIZE (Quantitative data)
- Stratified sampling – One location in ‘retreat the line’ management area, another in ‘hold the line’ management area
- Method:
1. Set out a grid on the beach 10m x 10m
2. Use a random no. generator to get 2 numbers e.g. 2 and 4.
3. Go along 2m and up 4m on the grid and pick up a piece of sediment.
4. Measure the longest axis of the pebble using callipers in cm.
5. Repeat this 10 times and get an average sediment size.
6. We also measured the roundness of the 10 pebbles by judging how round they were on Power’s Scale where 1 = very angular and 6 = very round
Test 3: What impacts have coastal management techniques had on coastal communities? PERCEPTION OF MANAGEMENT TECHS (Qualitative)
- Random sampling: asking 10 random people along the sea front at Swanage Beach
- Method: we asked 7 closed questions using a bi-polar scale. Our questions included:
- Are you concerned about coastal erosion here?
- Do you think coastal defences have benefited businesses, shops and homes in Swanage?
- Do you think coastal defences have benefited tourism in Swanage?
Answers: YES, SLIGHTLY, NO
Test 1: What impacts have coastal management techniques had on coastal processes? BEACH PROFILES (Quantitative data) –> CONCLUSION
- The ‘hold the line’ management of Swanage Bay through groynes and beach nourishment has created a steeper and wider beach than the ‘retreat the line’ section.
- The managed beach was 22m wide, 3m wider than where no management had occurred.
- Beach on managed section rose to 2.2m high, much higher than the 0.5m high in the unmanaged area - this is because the groynes have trapped sediment moving northwards along beach and has deposited material.
Test 2: What impacts have coastal management techniques had on sediment characteristics SEDIMENT SIZE (Quantitative data) –> CONCLUSION
- ‘hold the line’ management at Swanage has meant the sediment is larger than in the unmanaged ‘retreat the line’ section.
- The sediment in managed area is larger and more angular compared to in the unmanaged section - the sediment is larger and more angular as its trapped behind the groynes in the managed area and sediment is being added through nourishment.
- Also the cliff in unmanaged area is collapsing and adding small sand particles onto the beach, making the sediment smaller
Test 3: What impacts have coastal management techniques had on coastal communities? PERCEPTION OF MANAGEMENT TECHS (Qualitative) –> CONCLUSION
- Erosion is smth that ppl were very worried abt on the whole (66% very compared to 11% no).
- On the whole respondents said that the management had positively benefited business, shops and homes in Swanage & also 77% said it had been positive for tourism
- 67% of ppl said the hard management were unattractive to the town of Swanage.
Test 1: Impact on Beach gradient –> PROBLEMS
- Error reading the clinometer
- Not holding ranging pole straight.
- Only measuring once in retreat and once in managed
Test 1: Impact on Beach gradient –> ALTERNATIVES
- Systematic sampling every 2 metres up beach
- Digital clinometer on phone
- Use a spirit level
Test 2: Impact on beach sediment –> PROBLEMS
- Only measuring the longest axis of sediment
- Natural tendency to pick up larger sediment despite sampling
- Estimating shape of sediment using the Powers Index was difficult to be accurate
- Only measuring once in retreat and once in manage
Test 2: Impact on beach sediment –> ALTERNATIVES
- Measure all three axis
- Pick up 3 pieces from this point and take average
- Work in pairs to discuss which Powers Scale it was – photograph and annotate
Test 3: Impact on communities –> PROBLEMS
- We only really asked elderly ‘friendly’ people in reality despite random sampling
- Only doing it on one morning. Were tourists outnumbering locals? Did this represent local views?
Test 3: Impact on communities –> ALTERNATIVES
- Identify age groups and ask 3 young, 3 middle age, 3 elderly
- Repeat on other days/times e.g. Weekday for workers
