Coastal Systems and Landscapes - The coastal system

Summary

This video introduces the dynamic coastal system, explaining how coasts evolve through various marine, atmospheric, and terrestrial processes. It discusses the coast as an open system, where energy and sediment are constantly in flux. Key concepts like landforms, feedback mechanisms, and the division of the coastline into distinct zones—offshore, inshore, foreshore, and backshore—are explored. The video also delves into processes like erosion, deposition, and longshore drift, illustrating how they shape coastlines over different time scales. Ultimately, the coast is a constantly changing environment, influenced by both natural forces and human activity.

Takeaways

• 😀 The coast is a dynamic environment constantly changing due to various processes and influences over different time scales, from hours to millennia.
• 🌊 Coastal zones can be divided into specific areas: offshore, inshore, foreshore, backshore, and nearshore, each with distinct characteristics and processes.
• 🌍 The coastal system is an open system, where energy (waves, wind, tides) and sediment (from rivers, longshore drift) are inputs, and energy and sediment can be lost through various processes.
• ⚡ The coast experiences both positive and negative feedback mechanisms that influence its development and changes, such as beach recovery after storms (negative feedback) or dune erosion due to human activity (positive feedback).
• 🕰️ Changes in the coastal environment occur across a range of time scales: hours (tides), days (weather and wave changes), weeks to months (erosion and sediment transport), years (landform development), and millennia (sea-level changes).
• 🏖️ The foreshore, the area between high and low water marks, is one of the most dynamic parts of the coastline, affected by the rising and falling of tides twice a day.
• 🏝️ The backshore is the area above the high-water mark, where marine processes generally do not affect it, except during storms or through wind-driven processes.
• 🌐 The concept of sediment cells can be used to divide the coastline into manageable sections, similar to drainage basins, to understand sediment movement and coastline changes.
• 🏄‍♂️ Coastal feedbacks can be positive (amplifying changes) or negative (returning the system to equilibrium), each playing a critical role in shaping the coastline.
• 📏 Understanding coastal zones and processes is essential for predicting and managing coastal changes, including erosion, landform development, and human impact.

Q & A

What defines the coastal zone?

The coastal zone is defined as the narrow area where land and sea overlap, encompassing the transition between the sea and the land, along with the processes and landforms that develop in this dynamic environment.

Why is the coastline considered a dynamic environment?

The coastline is dynamic because it constantly changes due to a variety of factors, including atmospheric processes, terrestrial (land-based) processes, marine processes, and human activities. These inputs create ongoing changes over different time scales.

What are the time scales on which changes occur in the coastal system?

Changes in the coastal system occur on various time scales: hours (e.g., tides), days (e.g., weather affecting wave patterns), weeks or months (e.g., erosion and sediment transport), years (e.g., development of landforms like dunes and spits), and even millennia (e.g., sea level changes).

What is meant by the coastal system being an open system?

An open system means that the coastal zone has inputs and outputs of both energy and matter. Energy comes from waves, wind, tides, and currents, while sediment is brought by rivers, longshore drift, and other processes. Sediment can also be lost or transferred between areas along the coast.

What are the main stores within the coastal system?

The main stores in the coastal system are landforms, which can be either erosional (e.g., cliffs, caves, arches, and stacks) or depositional (e.g., beaches, sand dunes, and spits). These landforms store sediment and energy within the system.

How does the coastal system lose energy or sediment?

The coastal system can lose energy when waves dissipate their force as they crash onto a beach. Sediment may be lost when it is blown inland above the tidal limit or moved from one part of the coastline to another through processes like longshore drift.

What is the role of feedback mechanisms in the coastal system?

Feedback mechanisms in the coastal system either stabilize or amplify changes. Negative feedback helps return the system to equilibrium, while positive feedback amplifies changes, potentially leading to further erosion or loss of landforms.

Can you give an example of negative feedback in the coastal system?

An example of negative feedback is when a storm erodes a beach, causing destructive waves to remove sediment. This erosion leads to the formation of an offshore bar, which reduces wave energy, resulting in constructive waves that help restore the beach's sediment and return it to equilibrium.

Can you give an example of positive feedback in the coastal system?

Positive feedback can occur when tourists trample on vegetation on a sand dune. This leads to exposed sand, which is blown away by the wind. As more sand is lost, the vegetation struggles to regrow, causing even more sand to be lost, amplifying the problem.

How is the coastal zone divided into different sections?

The coastal zone is divided into several sections based on the interaction between waves and the seabed. These include the offshore zone (where waves don’t interact with the seabed), the inshore zone (where waves begin to interact with the seabed), the foreshore zone (between the high and low tide marks), the backshore zone (above the high tide mark), and the nearshore zone (the combined inshore and foreshore zones).