S5 Geography: Coastal Landforms — Tutor Lesson Plan (60 min, wave energy to spit, four errors)

2026-11-02

Tutor lesson-prep guides · Secondary geography (DSE)

Students can name a stack and cannot explain where the energy went. This lesson starts with wave energy and follows it along a real coastline, so each landform becomes a statement about where energy was concentrated or lost.

Objectives — the student can explain how wave steepness and refraction concentrate energy, describe the process of longshore drift with a swash and backwash diagram, sequence the formation of cliffs, wave-cut platforms, caves, arches and stacks, explain beach and spit formation as deposition, and calculate a drift rate and a growth rate from supplied figures.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Wave terms	Where does a wave break?	Where the water depth is less than about half the wavelength
Erosion processes	Name two ways the sea erodes rock.	Hydraulic action and abrasion
Prevailing wind	Which direction do waves usually come from in Hong Kong in winter?	From the east or northeast

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Hook	Two bays, one headland, one ruined path	Predict where the waves hit hardest
8-18 min	Scene 1	Wave speed, breaking and refraction	Draw the bending lines
18-30 min	Scene 2	Longshore drift with a swash and backwash	Get the direction right
30-42 min	Scene 3	Erosional sequence to stack	Put six stages in order
42-54 min	Scene 4	Beaches, spits and bars as deposition	Compute 20 metres per year
54-60 min	Exit check	Three items in section 08	Marked at once

03 Teaching script (read it out)

Scene 1: Energy first, landform second

A deep-water wave of 100 metres wavelength travels at about 12.5 metres per second; in 5 metres of water the speed falls to about 7 metres per second, because speed depends only on depth once the water is shallow. The wave slows, the crest steepens and it breaks. Refraction happens because the part of the crest in shallow water slows first, so the crest bends to become more parallel to the shore, and that is why energy is concentrated on headlands and spread out across bays.

Ask: “Why is the headland eroded and the bay built up?” Because refraction bends energy towards the headland, leaving the bay calmer and dominated by deposition.

Scene 2: Longshore drift is a conveyor belt

Waves arrive at an angle to the shore, so the swash carries sediment up the beach at that angle, while the backwash returns straight down the slope under gravity. The net result is sediment moved along the coast, about 3 metres a day, which is roughly 1095 metres a year on a steady coast. The direction follows the dominant wave approach, so where the prevailing wind changes with the season, drift can reverse in different parts of the year.

Warn: drift moves sediment along the shore, not offshore. A student who sends material out to sea has confused drift with a rip current.

Scene 3: Six stages, always in order

Hydraulic action and abrasion widen a joint into a cave; the cave is eroded through a headland to make an arch; the arch roof collapses to leave a stack; the stack is undercut to a stump; the cliff retreats and leaves a wave-cut platform at the base, covered at high tide. The platform is the evidence that the cliff used to stand further out, and the notch at the cliff foot shows where the present attack is happening. Sequence questions reward the words before, then, finally, and penalise a list with no linking.

Ask: “Which landform tells you the sea has been working for a long time?” The platform, because it records retreat over a long period at the present sea level.

Scene 4: Where deposition wins

Deposition happens where energy falls: in a bay sheltered by refraction, in the lee of a headland, or where a river adds sediment. A beach is a store of sediment that shifts with the season, wide in summer and stripped in storms. A spit grows across a change in coastline direction because drift continues while the shore turns away, and it ends in a hooked tip where a second current deflects it. With a supply of 2000 cubic metres a year and roughly 1000 cubic metres needed for 10 metres of growth, the spit extends about 20 metres a year; a salt marsh then forms in the sheltered water behind it.

Ask: “Why does the spit not close the bay?” Because the river or the tide keeps a channel open, and that is exactly why the tip curves.

04 Question types and worked steps

Type	Example	Steps	Answer
Wave energy	Explain why waves attack a headland more than a bay.	Refraction bends the crest towards the headland, concentrating energy	Energy is the controlling idea
Process	Describe longshore drift.	Swash at an angle, backwash straight down, net movement along the shore	Name both halves
Sequence	Put cave, arch, stack, stump in order.	Cave, arch, stack, stump.	Erosion of a joint at a headland
Calculation	Supply 2000 cubic metres a year, 1000 cubic metres per 10 metres. Find the growth rate.	Two units of 10 metres, so 20 metres a year	Check the units before dividing

Sanity check (teach this): Every landform answer must name the process and the energy condition, not just the shape: erosion where energy is high, deposition where it falls. For calculations the check is dimensional: cubic metres divided by cubic metres per metre gives metres. Any explanation that moves sediment in a direction contradicting the prevailing wave approach is wrong, however neat the diagram.

05 Independent practice (3 questions)

Question	Answer	What to watch
Explain why a wave bends as it approaches the shore.	The part of the crest in shallow water slows first, so the crest turns.	Refraction is due to speed change
A coast drifts 3 metres a day. Find the annual movement.	1095 metres.	Multiply by 365
Describe how an arch becomes a stack.	The roof of the arch collapses under its own weight and wave attack, leaving a detached pillar.	Two sentences, in order
Give two reasons a beach is wider in summer.	Gentler waves and more constructive swash; calmer weather brings less storm erosion.	Seasonal energy change

06 Common mistakes and what to say

Mistake	Student writes	Say this
Explaining refraction as waves hitting the headland	The crest bends because of the speed change, and the headland is where energy collects as a result	Ask which part of the wave slows first
Putting backwash at an angle	Backwash runs straight down the slope under gravity	Ask which force drives it
Saying drift moves sand offshore	Drift is along the shore; offshore movement belongs to rip currents and storm waves	Ask for the direction on the diagram
Listing landforms without process	Each stage needs the erosion or deposition mechanism named	Ask how, not what

07 Homework (paper, section and question numbers)

Secondary geography chapter index — Read this chapter with the rivers and the weathering chapters
HKDSE Geography Paper 1 practice paper — Coastal field study questions; redo section 05 questions 1 to 4 of this guide

08 Exit check (last 5 minutes)

Question	Answer	Decision
Where is wave energy concentrated and why?	On headlands, because refraction bends the crest towards them.	All correct: move to drift
State the two halves of longshore drift.	Angled swash and straight backwash, giving net movement along the shore.	Direction matters
Give one landform of coastal deposition and where it sits.	A spit, growing across a change in coastline direction.	Sheltered water behind it

09 Tutor FAQ

Do students need the wave speed formulas?

Not for DSE, but the idea that shallow water controls speed, and that refraction follows from it, is examinable.

Why is the platform important?

It is the evidence of cliff retreat and sea level history, which is exactly what extended-response questions ask for.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.