📚 Coastal Systems and Landscapes | 海岸系统与地貌景观
Coastal systems and landscapes are dynamic environments shaped by the interaction of wind, waves, tides, currents, geology, sediment supply and human activity. This revision guide covers the key Edexcel A-Level Geography content: energy sources, sediment cells, geomorphological processes, erosional and depositional landforms, sea level change and coastal management.
海岸系统与地貌景观是由风、波浪、潮汐、海流、地质条件、沉积物供应和人类活动共同塑造的动态环境。本复习指南涵盖 Edexcel A-Level 地理的核心内容：能量来源、沉积物单元、地貌过程、侵蚀与沉积地貌、海平面变化以及海岸管理。
1. Coasts as Natural Systems | 海岸作为自然系统
A coastal system is an open system with inputs, outputs, stores, flows and feedback loops. Inputs include energy from waves, wind, tides and currents, as well as sediment from rivers, cliffs and offshore sources. Outputs include sediment removed to deep water, evaporation and wave energy dissipation. The balance between inputs and outputs determines whether a coastline advances, retreats or stays in dynamic equilibrium.
海岸系统是一个开放系统，具有输入、输出、储存、流动和反馈回路。输入包括来自波浪、风、潮汐和海流的能量，以及来自河流、悬崖和近海的沉积物。输出包括被搬运到深水的沉积物、蒸发和波浪能量耗散。输入与输出之间的平衡决定海岸线是前进、后退还是处于动态平衡。
2. Sources of Energy at the Coast | 海岸能量来源
Wind is the main source of energy for wave generation. The size and energy of waves depend on wind speed, wind duration and fetch, which is the uninterrupted distance over which the wind blows. Tides are caused mainly by the gravitational pull of the Moon and Sun, producing periodic rises and falls in sea level. Tidal currents can transport sediment, especially in estuaries and tidal inlets. Coastal currents and longshore drift also move sediment along the shore.
风是波浪生成的主要能量来源。波浪的大小和能量取决于风速、风吹持续时间和风区长度，即风不受阻碍地吹过的距离。潮汐主要由月球和太阳的引力引起，造成海平面的周期性升降。潮流可以搬运沉积物，特别是在河口和潮汐通道中。沿岸流和沿岸漂移也会沿着海岸搬运沉积物。
3. Sediment Sources and Coastal Cells | 沉积物来源与海岸单元
Sediment in coastal systems comes from rivers, cliff erosion, seabed erosion, beach nourishment and biogenic sources such as shells and coral fragments. Sediment is stored in beaches, dunes, spits, bars, estuaries and nearshore bars. A coastal cell is a self-contained stretch of coastline where sediment is largely recycled between sources, transfers and sinks. Major boundaries, such as headlands or deep channels, prevent significant sediment transfer between adjacent cells. Understanding these cells helps manage erosion and beach sediment budgets.
海岸系统中的沉积物来自河流、悬崖侵蚀、海床侵蚀、海滩补沙以及贝壳和珊瑚碎屑等生物来源。沉积物储存在海滩、沙丘、沙嘴、沙坝、河口和近岸沙坝中。海岸单元是一段基本封闭的海岸线，沉积物主要在来源、转移和汇之间循环。主要的边界，如岬角或深水通道，会阻止相邻单元之间的大量沉积物转移。理解这些单元有助于管理侵蚀和海滩沉积物收支。
4. Weathering and Mass Movement | 风化与块体运动
Sub-aerial processes weaken and break down coastal rocks. Mechanical weathering includes freeze-thaw weathering, salt crystallisation and wetting and drying. Chemical weathering includes solution of limestone and oxidation of iron minerals. Biological weathering involves plant roots and burrowing animals. Mass movement is the downslope movement of rock and soil under gravity. Common types on coasts include rockfall, landslides, mudflows and rotational slumping. These processes supply sediment to the coastal system and can accelerate cliff retreat when combined with marine erosion.
陆上过程会削弱和破坏海岸岩石。机械风化包括冻融风化、盐结晶和干湿交替。化学风化包括石灰岩的溶蚀和铁矿物的氧化。生物风化涉及植物根系和穴居动物。块体运动是岩石和土壤在重力作用下的顺坡移动。海岸上常见的类型包括岩崩、滑坡、泥流和旋转滑动。这些过程为海岸系统提供沉积物，并在与海洋侵蚀结合时加速悬崖后退。
5. Marine Erosion Processes | 海洋侵蚀过程
Marine erosion breaks down and removes material from the coast. The main processes are hydraulic action, where air and water are forced into cracks by breaking waves; abrasion or corrasion, where rock fragments are hurled against cliffs; attrition, where particles collide and become smaller and rounder; and solution or corrosion, where seawater dissolves certain minerals. Wave pounding and cavitation can also contribute to erosion. Erosion is most effective during high-energy storm events and where cliffs are exposed to destructive waves.
海洋侵蚀会破坏并移除海岸物质。主要过程包括水力作用，即破碎的波浪将空气和水压入裂缝；磨蚀或磨蚀作用，即岩石碎块被抛向悬崖；磨圆作用，即颗粒相互碰撞而变小变圆；以及溶蚀或腐蚀作用，即海水溶解某些矿物。波浪冲击和空蚀也会促进侵蚀。侵蚀在高能风暴事件期间以及悬崖暴露于破坏性波浪的地方最为有效。
6. Transportation and Deposition | 搬运与沉积作用
Sediment is transported along the coast by longshore drift, which occurs when waves approach the shore at an angle. The swash carries sediment up the beach, while the backwash returns it straight down the slope, producing a zigzag movement. The main transportation processes are traction, saltation, suspension and solution. Deposition occurs when wave energy falls, for example in sheltered bays, behind spits or where river sediment enters the sea. Low-energy constructive waves build up beaches, while high-energy destructive waves remove sediment.
沉积物通过沿岸漂移沿海岸搬运，当波浪以一定角度接近海岸时就会发生这种情况。冲流将沉积物推上海滩，而回流则沿坡面直接返回，形成锯齿状运动。主要的搬运过程是推移、跃移、悬浮和溶解。当波浪能量降低时，例如在遮蔽的海湾、沙嘴后方或河流沉积物入海处，就会发生沉积。低能量的建设性波浪会堆积海滩，而高能量的破坏性波浪会移除沉积物。
7. Erosional Landforms | 侵蚀地貌
Erosional landforms are produced on high-energy coastlines where resistant and less resistant rocks alternate. Headlands and bays form because softer rocks such as clay erode faster than harder rocks such as chalk or granite. Caves, arches, stacks and stumps develop on headlands through hydraulic action and abrasion along joints and faults. Wave-cut platforms are gently sloping rocky surfaces left behind as cliffs retreat. Other features include geos, blowholes and cliffs with wave-cut notches.
侵蚀地貌形成于高能海岸线，那里软硬岩层交替分布。岬角和海湾的形成是因为黏土等较软岩石比白垩或花岗岩等较硬岩石侵蚀得更快。海蚀洞、海蚀拱、海蚀柱和海蚀残柱沿节理和断层经水力作用和磨蚀作用在岬角上发育。海蚀平台是悬崖后退后留下的平缓倾斜的岩石面。其他特征还包括海蚀沟、吹穴和带有海蚀凹槽的悬崖。
8. Depositional Landforms | 沉积地貌
Depositional landforms are built by constructive waves, longshore drift and abundant sediment supply. Beaches are accumulations of sand or shingle between high and low tide marks. Spits are long narrow ridges of sand or shingle attached to the land at one end and extending into the sea, often with a hooked end. Bars form when a spit joins two headlands across a bay, and tombolos connect an island to the mainland. Sand dunes develop behind beaches through aeolian transport and vegetation succession. Salt marshes and mudflats form in sheltered, low-energy environments such as estuaries and behind spits.
沉积地貌由建设性波浪、沿岸漂移和充足的沉积物供应形成。海滩是高潮线和低潮线之间沙或卵石的堆积体。沙嘴是狭长的沙或卵石脊，一端与陆地相连并向海中延伸，末端常呈钩状。沙坝是沙嘴跨越海湾连接两个岬角时形成的，连岛沙洲则将岛屿与大陆连接起来。沙丘通过风成搬运和植被演替在海滩后方发育。盐沼和泥滩形成于河口和沙嘴后方等遮蔽的低能环境。
9. Sea Level Change | 海平面变化
Sea level change can be eustatic, involving a global change in ocean water volume or temperature, or isostatic, involving local vertical land movement. During glacial periods, sea level fell because water was stored in ice sheets; after deglaciation, sea level rose. Isostatic rebound occurs when land rises after the removal of ice, while isostatic subsidence can occur as forebulges collapse. Emergent coastlines show raised beaches and relict cliffs, while submergent coastlines produce rias and fjords. Human-induced climate change is accelerating eustatic sea level rise through thermal expansion and melting ice sheets.
海平面变化可以是海面升降变化，涉及全球海水体积或温度的变化；也可以是地壳均衡变化，涉及局地的垂直陆地运动。在冰期，由于水储存在冰盖中，海平面下降；冰消期后，海平面上升。地壳均衡回弹是指冰盖移除后陆地上升，而地壳均衡沉降可能随着前隆的塌陷而发生。上升海岸表现为抬升海滩和残留悬崖，下沉海岸则形成溺谷和峡湾。人类活动引起的气候变化正在通过热膨胀和冰盖融化加速海面升降型海平面上升。
10. Coastal Management Strategies | 海岸管理策略
Coastal management aims to reduce erosion, flooding and habitat loss while balancing social and economic needs. Hard engineering uses artificial structures, such as sea walls, groynes, revetements and rock armour, to control waves and sediment. Soft engineering works with natural processes, including beach nourishment, dune stabilisation, managed retreat and wetland creation. Shoreline Management Plans set long-term policies for stretches of coast, choosing from hold the line, advance the line, managed realignment or no active intervention. Integrated Coastal Zone Management coordinates all stakeholders to achieve sustainable outcomes.
海岸管理旨在减少侵蚀、洪水和栖息地丧失，同时平衡社会和经济需求。硬工程使用人工构筑物，如海堤、丁坝、护岸和防波石，来控制波浪和沉积物。软工程则利用自然过程，包括海滩补沙、沙丘固定、管理性后退和湿地营造。海岸线管理计划为各段海岸制定长期政策，在保线、进线、管理性调整或不主动干预之间作出选择。海岸带综合管理协调所有利益相关方，以实现可持续的结果。
11. Case Study: Holderness Coast | 案例研究：霍尔德内斯海岸
The Holderness coast in East Yorkshire, England, is one of the fastest-eroding coastlines in Europe, retreating on average about 2 metres per year. The cliffs are made of soft boulder clay and are exposed to powerful North Sea waves and longshore drift. Key management schemes include rock armour and groynes at Mappleton, sea walls at Bridlington and Hornsea, and the controversial Spurn Head spit at the mouth of the Humber Estuary. This case study illustrates conflict between protecting property and allowing natural coastal processes to continue.
英格兰东约克郡的霍尔德内斯海岸是欧洲侵蚀最快的海岸线之一，平均每年后退约 2 米。悬崖由松软的冰砾泥组成，并暴露在强大的北海波浪和沿岸漂移之下。主要管理方案包括马普尔顿的防波石和丁坝、布里德灵顿和霍恩西的海堤，以及亨伯河口具有争议的斯珀恩角沙嘴。该案例研究说明了保护财产与允许自然海岸过程继续之间的冲突。
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