Geography K–10 · Years 9–10

How fast is this beach moving: shoreline change from annual satellite shorelines

Environmental change and management (ACARA Year 10 sub-strand); NSW Stage 5 focus area Environmental Change and Management (2015 syllabus) and Environmental change and management (2024 syllabus); coastal environment as the investigative study

Practical, model not builtLow risk

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The idea

Annual shorelines mapped from satellite imagery since 1988 show whether a coast is eroding or growing, and a line fitted through the positions gives the rate in metres per year.

What you need

DEA Coastlines on Digital Earth Australia Maps for a chosen NSW beach (annual shorelines and rates of change along the coast)
The map's measuring tool or a screen capture with its scale bar; a spreadsheet. DEA Coastlines maps annual shorelines from 30 m Landsat pixels by subpixel waterline extraction, and its product page states 7.3 m mean absolute error (10.3 m RMSE) for the median annual position, so a position read off the screen cannot be trusted to better than several metres; the rate-of-change points carry their own standard error (se_time, whose 95 per cent interval is se_time × 1.96) and a p value (sig_time), and DEA flags a rate as statistically significant at p of 0.01 or less.

How to do it

Open DEA Coastlines at the chosen beach and pick one location along the coast; draw a transect at right angles to the shoreline from a fixed landward point.
Along the transect, measure the distance from the landward point to each annual shoreline; record year and distance.
Plot distance against year and fit a straight line (spreadsheet trend line or the calculator); the slope is the rate in m per year, negative for retreat. Read DEA's own standard error and p value for that location and write the 95 per cent interval beside the class's slope.
Compare the class rate with the rate of change DEA Coastlines reports at that location.
Repeat at a second location on the same beach (for example near a river mouth or a rock wall) and compare.
Link the pattern to the beach profile survey and to management on that coast (walls, nourishment, dune fencing).

What you should see

A table of year and distance, a graph with a fitted line and a rate in m per year for two locations, compared with DEA's own rate. Year-to-year positions scatter around the line because each shoreline is one year's composite and storms move sand back and forth; the rate is the trend through the scatter. Arithmetic check of the line fitting only, and not a claim about the precision the data allows: positions 0, −1, −1 and −3 m in four consecutive years fit a line of slope −0.9 m per year. Annual positions cannot in fact be read to 1 m from this product, whose median annual position carries about 7 m mean absolute error, so the class states its rate with DEA's standard error beside it, and where the total change over the record is no larger than that error the finding is that no trend can be resolved at that location. It worked if both locations were measured from fixed landward points along lines at right angles to the coast.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A beach that looks the same each summer is not changing.
One stormy year shows the long-term trend of a coast.
A rate computed from the numbers is real even when it is smaller than the measurement error.

Safety card

Low riskLearners carry it out

Hazards

No hazard is listed.

Controls

No control is listed.

Note

No chemicals or heat are used. The activity is run under the school risk-assessment procedure; RiskAssess (riskassess.com.au) holds templates for school practicals and fieldwork. The NSW Department of Education Chemical Safety in Schools package is not triggered.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Geography K–10 Syllabus (2015), NESA; current and taught in 2026, replaced from 2027. The outcome codes are not printed on the NESA landing page for this syllabus, which only links the document, so the url given is the syllabus document itself (geography-k-10-syllabus-2015.docx); the code and its outcome text were read in that document on 23 September 2026.GE5-2 GE5-3 GE5-7
Geography 7–10 Syllabus (2024), NESA; implementation from 2027, not yet taught; code read on this page on 22 September 2026GE5-PRI-01 GE5-TAP-01
Australian Curriculum v9AC9HG10K04AC9HG10S02AC9HG10S03

Sources

The pages the author read to write this activity.

All Concept Studio activities