Measuring beach profile
Tape perpendicular + ranging poles + clinometer at each break of slope. Cross-section from back of beach to water's edge.
A beach profile is a cross-section showing the shape of a beach from the back of the beach to the water's edge.
Method (using ranging poles + clinometer):
- Lay a TAPE MEASURE perpendicular to the shoreline from the back of the beach to the water's edge (at low tide for accessibility).
- Identify visible BREAKS OF SLOPE along the transect — places where the beach gradient changes (back of beach, top of beach, mid-beach, swash zone).
- Place RANGING POLES at adjacent breaks of slope (one pole at each).
- Use a CLINOMETER to sight from one pole to the same height on the other pole. Read the angle (in degrees).
- RECORD: distance between poles + angle measured.
- Repeat for each pair of adjacent breaks of slope along the entire beach.
- PLOT a cross-section: elevation (calculated from angles + distances) vs distance from back of beach.
Alternative method using emery boards or sensors for more accurate measurement of fine-scale beach elevation.
Why measure beach profile?
- Tracks CHANGES over time (storms, seasons, before/after engineering).
- Identifies erosion or accretion areas.
- Informs management decisions (beach replenishment volumes; need for groynes).
- Compares between beaches (sand vs pebble; sheltered vs exposed).
Sources of error.
- Parallax error reading clinometer (eye not aligned correctly).
- Tide level affects which is 'the beach'.
- Storm changes can reshape beach overnight.
- Pole verticality — must be vertical for accurate readings.
Improvements.
- Same observer takes all readings (consistency).
- Multiple readings + means.
- Same time of tide for each visit.
Best practice: combine beach profile measurements with PHOTOGRAPHS at fixed points to track visual changes.
- Tape perpendicular + ranging poles + clinometer + tape between poles.
- Record breaks of slope + angles + distances.
- Plot cross-section: elevation vs distance.
- Track changes over time + before/after storms.
- Sources of error: parallax, tide level, storms.