Beach profile analysis

• To measure the transverse profile of the beach for a fixed-point set behind the beach down to the low water mark.
• Profiles can be taken at different times and locations to be compared to illustrate and quantify changes in the beach width, height, volume, and shape. 
• they can also be used to show the relationships between the beach profile and other factors – ex rock type, cliff profile and sediment size or shape.
• Equipment:

  • tape measure.
  • Clinometer
  • Ranging poles
  • A compass
  • A recording sheet.
• Methodology: General

  • Locate sampling points along the beach, visually noting the major changes to use as the basis for the sections and make a rough sketch. 
  • At each sampling point, identify and stake the reference point using a ranging pole, and make note of its location.
  • Use the compass to work out the orientation of the profile line. This will be perpendicular to the beach face. Make sure to maintain this moving along the profile.
  • Place the ranging pole at the end of the profile line – low tide mark (0m).
  • At each new section take a clinometer reading 
• Methodology: Slope analysis

  • Measure width of beach from strand line to back of beach using a tape measure
  • Using ranging poles to identify notable changes in beach slope.
  • Use ranging poles and a clinometer to measure angle of beach or alternatively use a smartphone app placed on a metre stick to give angles.
• Methodology: Infiltration rates

  • use a stopwatch to time how quickly.
  • 1ltr of water (in a bottomless plastic bottle) disappears
• Methodology: Porosity rates

  fill a 1ltr jug with sediment or sand and then add water to calculate the percentage of space between sand pebbles.
• Methodology: Sediment

  • Beach sediment (pebbles) should be sampled randomly (e.g. using a blindfold) and pebble axes can be measured using callipers and Callieux roundness cards
  • Finer sediment can be measured using sediment sieves and the percentage of material collected in each sieve can be calculated once each layer is weighed
• Methodology: Wave frequency

  Wave frequency can be measured by timing number of breaking waves to pass an object (e.g. ranging pole or offshore rock) in 1 minute.
• Considerations and limitations

  • Safety!
  • Awareness of tide times (in inaccessible locations) and the time needed to carry out field work needs to be assessed carefully.
  • Beach profiles can vary considerably during the year (storms cause more erosion) – may need to repeat over different seasons.
  • Difficulties using a clinometer with ranging poles, particularly in exposed/windy conditions. Ranging poles need to be held straight and not allowed to sink into the sand.
• Considerations and limitations:

  • Need to ensure pebbles are selected randomly to avoid human influence over selection – or use a blindfold.
  • User error, or lack of familiarity when using a clinometer can produce invalid readings.
• Processing techniques:

  • Beach transects/cross sections. 
  • Divided bar graphs to show porosity and 5 of sediment type (especially sand grain sizes)
  • Dispersion graphs for comparison of pebble sizes
  • Chi-squared can be used to prove a difference in sediment type between two beaches.
  • Change in beach or cliff position over time can be analysed using historical maps (secondary sources from a local reference library) or historical photographs.