📚 Introduction to Coastal Systems and Landscapes | 海岸系统与地貌导论
Coasts are dynamic interfaces where land, sea and atmosphere interact. In Edexcel A-Level Geography, the study of coastal systems and landscapes focuses on the flows of energy and sediment that shape shorelines over timescales ranging from seconds to millennia. Understanding these systems is essential for evaluating risks such as erosion, flooding and habitat change, as well as for designing sustainable management responses.
海岸是陆地、海洋和大气相互作用的动态界面。在 Edexcel A-Level 地理课程中，海岸系统与地貌的学习重点关注能量和沉积物的流动，它们在从数秒到数千年的不同时间尺度上塑造着海岸线。理解这些系统对于评估侵蚀、洪水、生境变化等风险，以及设计可持续的管理对策至关重要。
1. Defining Coastal Systems | 海岸系统的定义
A coastal system is an open system consisting of interacting components, including landforms, water, sediment, biota and human structures. The coast itself is often defined as the zone where terrestrial and marine processes meet, extending from the inland limit of wave influence to the offshore limit of sediment movement. This zone includes cliffs, beaches, dunes, estuaries and nearshore bars.
海岸系统是一个开放系统，由一系列相互作用的组成部分构成，包括地貌、水体、沉积物、生物和人工建筑物。海岸本身通常被定义为陆地过程和海洋过程交汇的地带，从波浪影响的内陆界限延伸到沉积物运动的外海界限。该地带包括悬崖、海滩、沙丘、河口和近岸沙坝。
Using a systems approach means examining how inputs, stores, transfers and outputs are linked, rather than treating individual landforms in isolation. Coastal systems also tend towards dynamic equilibrium, where inputs and outputs are balanced over time, although storms and human intervention can disturb this state.
采用系统方法意味着要考察输入、储存、转移和输出之间的联系，而不是孤立地看待单个地貌。海岸系统还趋向于动态平衡，即输入和输出在一段时间内保持平衡，尽管风暴和人类干预会打破这种状态。
2. The Coast as an Open System | 海岸作为开放系统
The coast receives inputs of energy and sediment, transfers and stores them within coastal landforms, and releases outputs to other systems. Energy inputs include wind, waves, tides and currents, while sediment inputs come from rivers, cliff erosion, seabed erosion and beach nourishment. Outputs include sediment transported offshore or alongshore and heat or moisture transferred to the atmosphere.
海岸接收能量和沉积物的输入，在海岸地貌中进行转移和储存，并向其他系统释放输出。能量输入包括风、波浪、潮汐和洋流，而沉积物输入来自河流、悬崖侵蚀、海床侵蚀和海滩补沙。输出包括向离岸或沿岸方向搬运的沉积物，以及向大气传递的热量或水分。
Because matter and energy cross its boundaries, the coastal system is open rather than closed. Stores such as beaches, dunes and spits hold sediment for varying periods of time. The balance between inputs and outputs is described by the sediment budget, and when inputs exceed outputs the coast builds seaward; when outputs exceed inputs the coast retreats.
由于物质和能量跨越边界流动，海岸系统是开放系统而非封闭系统。海滩、沙丘和沙嘴等储存体在不同时间尺度上储存沉积物。输入与输出之间的平衡用沉积物收支来描述：当输入超过输出时，海岸向海推进；当输出超过输入时，海岸线向陆后退。
3. Energy Inputs: Winds, Waves and Tides | 能量输入：风、波浪与潮汐
Waves are the dominant energy input for most coastlines. They are generated primarily by wind, and their energy depends on wind speed, duration and fetch. Wave height, wave length and wave period determine whether a wave is constructive or destructive, and these characteristics influence whether sediment is moved onshore or offshore. In simple terms, wave energy is proportional to the square of wave height.
波浪是大多数海岸线最主要的能量输入。波浪主要由风产生，其能量取决于风速、风时和风区长度。波高、波长和波周期决定波浪是建设性波浪还是破坏性波浪，这些特征还影响沉积物是向岸还是离岸运动。简单来说，波浪能量与波高的平方成正比。
E ∝ H²
Tides, caused by the gravitational pull of the Moon and Sun, produce regular changes in water level that expose different parts of the coastal zone to wave action. A large tidal range creates a wider intertidal zone, whereas a small tidal range concentrates wave energy on a narrower band. Currents move water and sediment both alongshore and offshore, linking one part of the coast to another.
潮汐由月球和太阳的引力引起，产生有规律的水位变化，使海岸带不同部位受到波浪作用。潮差大，潮间带就更宽；潮差小，波浪能量则集中在较窄的范围内。洋流沿着沿岸和离岸方向搬运水和沉积物，把海岸的一个部分与另一个部分联系起来。
4. Sediment Sources and Sediment Cells | 沉积物来源与沉积物单元
Sediment is a central concept in coastal systems. It can be sourced from rivers, cliff erosion, seabed sediments, glacial deposits and biological material such as shells. Sediment may be sand, shingle, mud or larger material, and its size and shape influence how easily it is eroded, transported and deposited.
沉积物是海岸系统的核心概念。沉积物可以来自河流、悬崖侵蚀、海床沉积物、冰川沉积物以及贝壳等生物物质。沉积物可能是沙、砾石、泥或更大的颗粒，其大小和形状影响其被侵蚀、搬运和堆积的难易程度。
In England and Wales, the coastline is divided into sediment cells: large, largely self-contained units within which sediment movement is contained. There are eleven primary sediment cells in England and Wales, each divided into smaller sub-cells. This concept helps managers understand that interrupting sediment supply in one place can cause erosion elsewhere, because the sediment budget is a closed system at the cell scale.
在英格兰和威尔士，海岸线被划分为沉积物单元，即沉积物运动在很大程度上被封闭在其中的大型独立单元。英格兰和威尔士共有十一个主要沉积物单元，每个单元又分为更小的子单元。这一概念有助于管理者理解，在一处打断沉积物供应可能导致其他地方发生侵蚀，因为在单元尺度上沉积物收支是一个闭合系统。
5. Coastal Processes: Erosion, Transportation and Deposition | 海岸过程：侵蚀、搬运与堆积
Coastal processes can be grouped into erosion, transportation and deposition. Marine erosion operates through hydraulic action, abrasion, attrition and solution. Hydraulic action is the force of water compressing air into cracks; abrasion is the sandpaper effect of sediment grinding against rock; attrition is the wearing down of sediment particles themselves; and solution dissolves soluble rock minerals.
海岸过程可分为侵蚀、搬运和堆积。海蚀通过水力作用、磨蚀、磨损和溶蚀进行。水力作用是水将空气压入裂缝的力量；磨蚀是沉积物像砂纸一样磨蚀岩石；磨损是沉积物颗粒自身被磨圆变细；溶蚀则溶解可溶性岩石矿物。
Transportation takes place by traction, saltation, suspension and solution, often following the direction of longshore drift. Deposition occurs when energy falls, for example in sheltered bays, estuaries or behind spits. The balance between erosion and deposition determines whether a coastline advances, retreats or remains broadly stable.
搬运以推移、跃移、悬移和溶移的方式进行，通常沿着沿岸漂沙的方向。当能量下降时，例如在遮蔽海湾、河口或沙嘴后方，就会发生堆积。侵蚀与堆积之间的平衡决定海岸线是前进、后退还是大致保持稳定。
6. Feedback Mechanisms in Coastal Systems | 海岸系统中的反馈机制
Feedback mechanisms regulate coastal change. Negative feedback reduces the effect of a disturbance and tends to restore equilibrium. For instance, if a beach is eroded during a storm, the stored sediment is deposited offshore as a bar, causing waves to break earlier and reducing further erosion.
反馈机制调节着海岸变化。负反馈减少干扰的影响，并倾向于恢复平衡。例如，如果海滩在风暴中受到侵蚀，储存的沉积物会在离岸处沉积为沙坝，使波浪更早破碎，从而减少进一步侵蚀。
Positive feedback amplifies change and moves a system away from its previous state. Once a protective dune is breached, water and wind may enlarge the gap, leading to more erosion and eventually a washover fan. Recognising these feedbacks is important because human structures can unintentionally trigger positive feedback, such as terminal scour at the end of a sea wall.
正反馈则放大变化，使系统远离原有状态。一旦防护沙丘被冲破，水流和风可能扩大缺口，导致更多侵蚀，最终形成越浪扇。认识这些反馈很重要，因为人类建筑物可能无意中触发正反馈，例如海堤末端冲刷。
7. Coastal Landforms: Erosional Landscapes | 海岸地貌：侵蚀地貌
Erosional landforms develop where wave energy is high and rock is relatively resistant. Headlands and bays form on discordant coastlines, where alternating bands of hard and soft rock are eroded at different rates. The softer rock erodes more quickly to form bays, while harder rock remains as headlands.
侵蚀地貌形成于波浪能量高、岩石相对坚硬的地方。岬角和海湾形成于不整合海岸线，那里硬岩和软岩交替分布，被侵蚀的速度不同。软岩侵蚀较快形成海湾，硬岩则残留为岬角。
Cliffs, wave-cut platforms, caves, arches, stacks and stumps represent an evolutionary sequence. Caves form at weaknesses such as joints or faults, enlarge into arches, and when an arch collapses it leaves a stack; the stack is then eroded into a stump. The rate of retreat is influenced by rock type, geological structure, wave energy and sub-aerial processes such as weathering and mass movement.
悬崖、海蚀平台、洞穴、拱门、海蚀柱和海蚀残丘代表了一个演化序列。洞穴在节理或断层等软弱处形成，扩大成拱门，拱门坍塌后留下海蚀柱，海蚀柱再被侵蚀成海蚀残丘。后退速度受岩石类型、地质构造、波浪能量以及风化、块体运动等陆上过程的影响。
8. Coastal Landforms: Depositional Landscapes | 海岸地貌：堆积地貌
Depositional landforms develop where sediment supply exceeds erosion or where wave energy is reduced. Beaches are accumulations of sand or shingle between low and high water marks; they may be swash-aligned or drift-aligned. Spits are elongated ridges of sand or shingle attached to the land at one end, formed by longshore drift.
堆积地貌形成于沉积物供应超过侵蚀或波浪能量减弱的地方。海滩是位于低潮线和高潮线之间的沙或砾石堆积体，可能是冲流对齐型或漂沙对齐型。沙嘴是一端与陆地相连的狭长沙砾脊，由沿岸漂沙形成。
Barrier beaches and tombolos extend further across bays or towards islands. Salt marshes and sand dunes are vegetated depositional features that develop in sheltered intertidal or backshore zones. Their formation depends on sediment availability, vegetation succession and time, and they provide important habitats as well as natural coastal protection.
滨外沙坝和连岛沙洲延伸得更远，横跨海湾或连接岛屿。盐沼和沙丘是发育在遮蔽的潮间带或后滨地带的有植被生长的堆积地貌。它们的形成取决于沉积物供应、植被演替和时间，并提供重要生境以及天然海岸防护。
9. Sea-Level Change and Coastal Systems | 海平面变化与海岸系统
Sea-level change can be eustatic, driven by changes in ocean water volume or basin shape, or isostatic, caused by local land uplift or subsidence. Emergent coasts, such as raised beaches, form where land rises or sea level falls, while submergent coasts, such as rias and fjords, form where sea level rises or land sinks.
海平面变化可以是海动型的，由海洋水体体积或海盆形状的变化引起；也可以是地壳均衡型的，由局部陆地抬升或沉降引起。上升海岸（如抬升海滩）形成于陆地上升或海平面下降的地方，而沉降海岸（如里亚式海岸和峡湾）形成于海平面上升或陆地下沉的地方。
Contemporary climate change accelerates sea-level rise through thermal expansion of seawater and melting of land ice. This increases flood risk and coastal erosion on low-lying coasts, and it intensifies the problem of coastal squeeze, where natural habitats are trapped between rising seas and fixed defence structures.
当代气候变化通过海水热膨胀和陆地冰川融化加速了海平面上升。这增加了低洼海岸的洪水和侵蚀风险，并加剧了海岸挤压问题，即自然生境被上升的海平面与固定的防御工事夹在中间。
10. Human Impacts on Coastal Systems | 人类活动对海岸系统的影响
Human activities modify coastal systems by altering sediment supply, changing wave energy and adding hard structures. Dams and river engineering reduce sediment delivery to coasts, while port breakwaters and groynes interrupt longshore drift. Urbanisation replaces natural dunes and marshes with impermeable surfaces, and sea defences can cause terminal scour or transfer erosion down-drift.
人类活动通过改变沉积物供应、改变波浪能量和增加硬质建筑物来改变海岸系统。水坝和河流工程减少了输送到海岸的沉积物，港口防波堤和丁坝打断了沿岸漂沙。城市化用不透水地面取代了天然沙丘和沼泽，海防工程可能导致末端冲刷或使侵蚀向下游转移。
Sea walls, groynes and revetments protect local areas but often exacerbate erosion elsewhere by starving beaches of sediment. Climate change and sea-level rise further complicate these impacts, especially on densely populated coasts where the value of property and infrastructure is high.
海堤、丁坝和护岸保护了局部地区，但往往通过切断海滩的沉积物供应而加剧了其他地方的侵蚀。气候变化和海平面上升使这些影响更加复杂，尤其是在人口密集、财产和基础设施价值较高的海岸地区。
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