Coastal landscape development

Welcome to the Dynamic World of Coasts!

Welcome! In this chapter, we are going to explore the coastal zone. Think of the coast as a "battleground" where the land meets the sea. It is one of the most exciting areas in Geography because it is constantly changing. Some parts are being eaten away by powerful waves, while others are growing as the sea drops sand and shingle.

Don't worry if some of the terms seem long—we will break them down into simple pieces. By the end of these notes, you’ll understand how those famous cliffs, sandy beaches, and weirdly shaped rocks (like arches and stacks) actually formed!

1. Coasts as a System: The Big Picture

Geographers look at the coast as a system. You can think of a system like a factory: it has things coming in (inputs), things happening inside (processes), and things produced (outputs).

Inputs, Outputs, and the "Sediment Budget"

The "stuff" moving through this factory is mainly sediment (sand, silt, and pebbles).

• Inputs: Where the sediment comes from. Examples: eroding cliffs, rivers bringing mud to the sea, or waves bringing sand from offshore.
• Outputs: Where the sediment goes. Example: sediment being blown inland to form dunes or being washed out into the deep ocean.
• Stores: Where sediment sits for a while, like a beach or a sand dune.

The "Bank Account" Analogy:
Think of the Sediment Budget like a bank account.
- Inputs are deposits (putting money in).
- Outputs are withdrawals (taking money out).
- If you put in more than you take out, your beach "grows" (this is called positive budget or accretion).
- If the sea takes more than it gives, your beach shrinks (negative budget or erosion).

Quick Review: When the inputs and outputs are balanced, the coast is in dynamic equilibrium. It’s like a person on a treadmill—they are moving, but they stay in the same place!

2. The Power Behind the Change: Waves and Energy

Waves are the "engine" that drives coastal change. They get their energy from the wind blowing over the water.

Constructive vs. Destructive Waves

Not all waves are the same. Some build beaches, while others destroy them.

• Constructive Waves: These are "calm" waves. They are low in height and have a strong swash (water moving up the beach) and a weak backwash (water pulling back). They "construct" the beach by leaving sediment behind.
• Destructive Waves: These are "angry" waves. They are tall, frequent, and have a weak swash but a very strong backwash. They "destroy" the beach by dragging sand away.

Memory Aid:
Constructive waves Create beaches.
Destructive waves Drag them away.

3. Landscapes of Erosion: Carving the Land

When the sea attacks the land, it creates erosional landforms. This usually happens on high-energy coasts where waves are powerful.

The "Big Five" Processes of Erosion

1. Hydraulic Action: Air is trapped in cracks in the cliff. When a wave hits, the air is compressed, then expands violently as the wave retreats, "blasting" the rock apart.
2. Wave Quarrying: The sheer weight of the water hitting the cliff is enough to scoop out loose rocks.
3. Abrasion (or Corrasion): Waves fling pebbles and rocks against the cliff, acting like sandpaper.
4. Attrition: Rocks in the sea knock against each other, becoming smaller, smoother, and rounder.
5. Solution (Corrosion): Saltwater dissolves certain types of rock, like limestone.

Step-by-Step: The Cave, Arch, Stack, Stump Sequence

This is a classic exam topic! It shows how a headland (a piece of land sticking out into the sea) changes over time:

1. Cracks: Waves attack weaknesses (faults) in the headland via hydraulic action.
2. Cave: The crack grows into a cave.
3. Arch: Erosion breaks through the back of the cave, creating a hole you can see through (the arch).
4. Stack: The roof of the arch becomes too heavy and collapses, leaving a pillar of rock standing alone in the sea.
5. Stump: The stack is eroded at the base until it falls over, leaving a small "stump" visible only at low tide.

Did you know? Old Harry Rocks in Dorset is one of the most famous examples of this sequence in the UK!

4. Landscapes of Deposition: Building the Land

When the sea loses energy, it drops its load. This creates depositional landforms. This usually happens in low-energy coasts (like sheltered bays).

Longshore Drift (LSD)

Before we look at the shapes, we need to know how sediment moves. Longshore Drift is the process where waves move sand along the coastline in a "zigzag" pattern because the wind hits the coast at an angle.

Key Depositional Features

• Beaches: The most common feature. They can be sandy (flat and wide) or shingle (steep and narrow).
• Spits: A long, thin ridge of sand or shingle that sticks out into the sea, usually where the coastline changes direction (like a river mouth). Example: Spurn Head, East Yorkshire.
• Tombolos: A spit that grows so long it connects an island to the mainland. Analogy: It’s like the island is "holding hands" with the coast.
• Offshore Bars: A ridge of sand parallel to the coast, usually underwater or only visible at low tide.
• Sand Dunes: Hills of sand blown inland by the wind and trapped by plants like Marram Grass.

Quick Review: Deposition happens when waves slow down. This can be caused by shallow water, sheltered bays, or when a river meets the sea.

5. Estuaries and Saltmarshes

In sheltered areas like estuaries (where a river meets the sea), we find mudflats and saltmarshes. These are very "squelchy" environments!

How they form:
1. Silt and mud are deposited by the tide (this is called flocculation—where tiny clay particles stick together and get heavy).
2. Salt-tolerant plants (halophytes) start to grow.
3. These plants trap more mud, and the land slowly builds up above the sea level.

6. Sea Level Change: Why is the Coast Moving?

Sea levels aren't fixed. They change for two main reasons, and it's easy to mix them up!

Eustatic vs. Isostatic (The Easy Way)

• Eustatic Change (Global): This is a change in the actual volume of water in the ocean.
  Think of it like: Turning the tap on or off in a bathtub. (Caused by melting ice caps or thermal expansion).
• Isostatic Change (Local): This is a change in the level of the land itself.
  Think of it like: A heavy person sitting on a sofa—the cushion goes down. When they stand up, the cushion pops back up. (Caused by heavy ice sheets weighing the land down, then melting).

Landforms of Sea Level Change

1. Submergent Coastlines (Sea level rises/Land sinks):
- Rias: Drowned river valleys (wide, V-shaped).
- Fjords: Drowned glacial valleys (very deep, U-shaped with steep sides).
- Dalmatian Coasts: Valleys running parallel to the coast are flooded, leaving a string of long, thin islands.

2. Emergent Coastlines (Sea level falls/Land rises):
- Raised Beaches: Former beaches that are now high above the current sea level. You might even see old sea caves halfway up a cliff!

7. Human Impact and Management

Humans often try to stop the "battle" between land and sea to protect homes and businesses. We call this Coastal Management.

• Hard Engineering: Using man-made structures like concrete Sea Walls or rock Groynes. These are expensive and often look "ugly," but they are strong.
• Soft Engineering: Working with nature. Examples include Beach Nourishment (dumping more sand on a beach) or Sand Dune Regeneration. These are cheaper and more natural but need constant maintenance.

The "Big Takeaway" on Management: Modern geography focuses on Sustainable Management. Instead of just building walls everywhere, we use Shoreline Management Plans (SMPs) to decide which areas are worth saving and which should be allowed to erode naturally (Strategic Realignment).

Final Summary: Key Takeaways

1. Systems: Coasts have inputs (sediment), processes (erosion/transport), and outputs.

2. Waves: Constructive waves build; Destructive waves erode.

3. Erosion: Creates headlands, cliffs, arches, and stacks.

4. Deposition: Creates beaches, spits, and tombolos when the sea loses energy.

5. Sea Level: Eustatic (water level) and Isostatic (land level) changes create drowned or raised landscapes.

Don't worry if this seems like a lot of information! Just remember that the coast is always trying to reach a balance. Every time a cliff erodes, that sediment is used to build a beach somewhere else!