2.5 - Coastal fieldwork

Why Llandudno?

• Location can be reached within day trip from Manchester

• Shingle beach - possible to measure difference in sediment size + shape, not possible on sandy beach

• Accessible location - no access issues/dangers associated with getting onto beach

• Plenty of space for data collection in groups

• Opportunities to make comparisons between western + eastern sections of beach

Managing health and safety

• Dress appropriately for weather e.g. sensible shoes

• Point side of ranging pole facing downwards

• Stay away from cliff, might collapse on you

• Stay in groups - stay safe, don’t get lost

• Map - don’t get lost

Enquiry questions

How does size + shape of sediment change with distance from sea?

• Particles get bigger as you move further from sea

How does beach slope angle change with distance from sea?

• Angle increases with distance from sea

Shingle beach

• Large sediment size

• Steep angle

• Particles deposited by swash

• Water drains down through large spaces between particles so backwash won’t carry sediment back out to sea

• Sediment therefore piles up on beach, creating steeper beach

Sandy beach

• Small particle size

• Flatter angle

• Water doesn’t drain through closely packed sand so backwash carries more material back out to sea

Primary data

Data you collect yourself
e.g. pebble measurements, questionnaire response, photos

Secondary data

Data from another source, including published data
e.g. census results, historical data and data collected by others

Quantitative data

Data that records quantities
e.g. numbers, sizes, frequencies

Qualitative data

Data that records subjective qualities
e.g. opinions, attitudes

Primary quantitative data collection methods

• Measurement of beach sediment size

• Measurement of beach slope angles

• Classification of sediment index using Powers Index of Roundness

Primary qualitative data collection methods

• Annotated photos of beach and sediment features

• Annotated field sketches

Secondary data collection methods

• Local geology map

• News articles about north shore beach

• Table of tide times (important for planning)

Sampling

Process of collecting data from a selection of sites/people to obtain a perspective on the wider area/population
Applicable to both quantitative and qualitative methods

Sample size

Minimum number of questionnaires/pebbles to be a representative sample because it isn’t possible to measure every pebble/ask every person

min. 25 pieces of data, allows you to carry out statistical test to find out if answer has occurred by chance or is it likely to be an accurate pattern

95% reliability in Geog

Random sampling

Each location/member of population is equally likely to be included

Systematic sampling

Observations are taken at regular intervals, such as every 10m or every 5th person

Stratified sampling

A proportionate number of observations is taken from each part of population/study area

Accuracy

How close a measurement is to true value, inaccurate results lead to inaccurate conclusions

Reliability

The extent to which results are consistent
If you repeated data collection, would you get same results and conclusion?

Validity

• Valid data collection method is appropriate to aim of investigation

• Valid data presentation technique is appropriate for data set in question

• Valid conclusion follows on logically from results and links back to original aim of enquiry

Tape measure

• To measure width of beach between start point (next to sea) and end point (base of promenade)

• To measure distances between data collection points

Ruler

To measure size (in mm along longest axis) of pieces of sediment

Clinometer

To measure slope angle between two points on beach

Ranging poles

To ensure accuracy + consistency when measuring slope angle between two points on beach

Copy of Powers Index of Roundness

To classify shape of piece of sediment

Data recording sheet

To record results in organised fashion, allowing for easier + more effective collation and analysis

Phone

To take photos of study area (qualitative data)

Measuring sediment size and shape

1. Measure total width of beach using tape measure
   Start at safe distance from water’s edge and finish at base of promenade

2. Divide total distance by 10 to give regular intervals at which to collect data (systematic sampling)

   e.g. beach width of 50m would give interval of 5m

   Site 1 is at 0m (close to water), Site 11 is finishing point (base of promenade)

3. At each site, collect 10 pieces of sediment

   a. Measure each piece of sediment in mm along longest axis using ruler and record result

   b. Classify each piece of sediment according to Powers Index of Roundness and record result

4. Repeat for each site

Measuring beach slope gradient

1. Study beach carefully and decide where changes in slope angle occur
   Likely to be several changes in slope angle between sea and promenade

2. Work in pairs, with each person holding ranging pole
   One person should stand at start point and one person should stand at position of first change in slope angle
   Hold poles up straight
   Measure horizontal distance between ranging poles carefully using tape measure (ensure it’s horizontal + taut)

3. Slope angle can measured by lining up clinometer between two points of exactly same height on ranging poles

   Record slope angle

4. Repeat for each location where slope angle changes

Photographs and field sketches

Take photos of study area and of data collection being carried out

Make a sketch of beach where data collection took place

Annotate sketch with relevant info, such as:

• Points where slope angle changes

• Observations about sediment sizes/shapes

• Important coastal features visible

• Physical/human influences that might have had impact on beach

Accuracy of data collection

• Weather - questions smaller sample size

• Tide time - beach size

• No. of transects

• Average/mean (human error)

• Instruments/measuring - tape measure

• 25 data points

• Anomalies

• Human impact - other students moving around rocks

Reliability of data collection

• One day/few hours (small sample size)

• Time restraint

• Secondary data

• Sample size

Presenting info on sediment size + shape

• Draw line graph to show how mean sediment size changes with distance from sea

• Draw line graph/bar chart to show how shape of sediment changes from site to site

• Draw divided bar chart to show how % of sediment in each shape category changes with distance from start point

• Compare data sets collected from western + eastern sections of north shore beach

Presenting info on beach slope gradient

• Construct beach profile using gradient measurmenets and distances between each change in slope angle
  Need protractor + graph paper

• Compare beach profiles drawn for western + eastern sections of north shore beach

Combining data on sediment characteristics and beach slope gradient

• Add pie charts to a copy of beach profile to show how sediment size + shape changed with distance from start point

  • Location of each pie chart on diagram should match site at which data was collected

  • Area of circle used for each pie chart should be in proportion to mean sediment size at that site

  • Each pie chart should be divided into categories from Powers Index of Roundness

• Compare diagrams drawn for western + eastern sections of north shore beach

Conclusion: how sediment size + shape changes with distance from sea

Along majority of beach transects, sediment tended to increase in both size and angularity with distance from sea

• Positive correlation between distance from sea and sediment size + angularity

Conclusion: how slope angle changes with distance from sea

Along majority of beach transects, slope angle tended to be shallower close to sea + steeper further from sea

• Appeared to be some relationship with sediment size, larger sediment corresponding to steeper gradient

• Beach profiles were often quite complex, with several changes in gradient and a number of ridges/berms rather than simple increase in gradient from sea to back of beach

Conclusion: difference between eastern and western ends of bay

Trends in sediment characteristics + beach profile were stronger/clearer at eastern end of bay

• Less human influence

• Fewer rocks have been added as coastal defence measure, allowing more ‘natural’ coastal processes and patterns to develop