Coastal Systems and Processes | 海岸环境系统与作用过程

📚 Coastal Systems and Processes | 海岸环境系统与作用过程

The coastal zone is one of the most dynamic environments on Earth, representing a complex open system where land, sea, and atmosphere interact continuously. It is characterised by inputs of energy from waves, tides, and winds, and by inputs of sediment from rivers, cliffs, and offshore sources. Within this system, energy and material are transferred, stored, and transformed, producing a distinctive suite of landforms that evolve over different timescales.

海岸带是地球上最具活力的环境之一，它是一个复杂的开放系统，陆地、海洋与大气在此持续相互作用。其特点在于波浪、潮汐和风等能量的输入，以及河流、悬崖和近海来源的沉积物输入。在该系统内部，能量与物质不断被传递、储存和转化，形成了一系列独特的地貌形态，并在不同的时间尺度上持续演变。

1. The Coastal System as an Open System | 作为开放系统的海岸环境

A coastline is best understood as an open system with inputs, stores, transfers, and outputs. Inputs include kinetic energy from prevailing winds and wave action, potential energy from tidal movements, and sediment from marine, terrestrial, and biological sources. Stores include beaches, dunes, spits, and offshore sandbanks, while transfers involve processes such as longshore drift, tidal currents, and aeolian transport. Outputs include sediment lost to deep water, sand blown inland, and energy dissipated through wave breaking and friction.

海岸线最好被理解为一个具有输入、存储、传输和输出的开放系统。输入包括盛行风和波浪作用的动能、潮汐运动的势能，以及来自海洋、陆地和生物来源的沉积物。存储包括海滩、沙丘、沙嘴和近岸沙洲；传输涉及如沿岸漂移、潮流和风成搬运等过程；输出则包括沉积物流失至深水区、吹向内陆的沙粒，以及通过波浪破碎和摩擦耗散的能量。

The systems approach emphasises dynamic equilibrium: when inputs or outputs change, the system adjusts its internal stores and transfers to restore balance. For example, if river sediment supply declines, beaches may erode; conversely, an increase in storm frequency may mobilise more sediment and reshape the coastline.

系统方法强调动态平衡：当输入或输出发生变化时，系统会调整其内部存储和传输以恢复平衡。例如，如果河流输沙减少，海滩可能遭受侵蚀；反过来，风暴频率增加可能使更多沉积物被搬运，并重塑海岸线形态。

Coastal system = Energy inputs + Sediment inputs → Transfers → Stores → Outputs

海岸系统 = 能量输入 + 沉积物输入 → 传输 → 存储 → 输出

2. Wave Energy and Wave Types | 波浪能量与波的类型

Waves are the primary source of energy in coastal systems. They are generated by wind blowing over the sea surface, with their size determined by wind speed, wind duration, and fetch (the distance over which the wind travels). Wave energy is proportional to the square of wave height, making larger waves significantly more powerful agents of geomorphic change.

波浪是海岸系统中主要的能量来源，由风吹过海面时产生。波浪的大小取决于风速、风的持续时间和风区距离（即风在海面上吹过的距离）。波能与波高的平方成正比，因此较大的波浪是地貌变化更强大的动力。

Constructive waves are characterised by a strong swash and weak backwash, low frequency (6–8 per minute), and low height. They build up beaches by depositing sediment. In contrast, destructive waves have a strong backwash and weak swash, high frequency (10–14 per minute), and greater height. They scour sediment from the beach, causing net erosion.

建设性波的特点是激浪强、回流弱，频率低（每分钟6–8次），波高小。它们通过沉积物堆积来加积海滩。相比之下，破坏性波回流强、激浪弱，频率高（每分钟10–14次），波高大。它们从海滩表面冲刷沉积物，造成净侵蚀。

Wave refraction concentrates wave energy on headlands and disperses it in bays. This explains why headlands are often eroded to form cliffs, whereas bays develop sandy beaches in lower-energy environments.

波浪折射使波能集中作用于海岬，并在海湾中分散。这解释了为何海岬常被侵蚀形成悬崖，而海湾则在较低能量环境中发育出沙滩。

3. Tides and Tidal Currents | 潮汐与潮流

Tides are the periodic rise and fall of sea level caused by the gravitational pull of the moon and sun. They influence coastal processes in several ways: they determine the vertical extent of wave action, control the movement of water and sediment in estuaries, and regulate the exposure of intertidal zones.

潮汐是月球和太阳引力引起的海面周期性升降。它从多个方面影响海岸过程：决定波浪作用的垂直范围，控制河口水和沉积物的运动，并调节潮间带的出露。

Spring tides occur when the sun, moon, and Earth are aligned, producing higher high tides and lower low tides; neap tides occur at right angles, with reduced tidal range. A large tidal range means that waves act over a wide vertical zone, spreading energy across a broader area and limiting the height of beach features. Diurnal, semi-diurnal, and mixed tidal regimes exist around the world, affecting sediment transport and the ecology of salt marshes.

当太阳、月球和地球排成一线时发生大潮，潮差更大；当三者成直角时发生小潮，潮差较小。大的潮差意味着波浪在宽广的垂直区域内作用，能量在更大面积上分散，从而限制了海滩地貌的高度。世界各地存在日潮、半日潮和混合潮等不同类型的潮汐，影响沉积物输运和盐沼生态。

4. Sediment Sources and the Sediment Budget | 沉积物来源与沉积物收支

Coastal sediment comes from a variety of sources: river discharge, cliff erosion, offshore deposits reworked by waves, biological material such as shell fragments and coral debris, and, in some regions, glacial till from previous ice ages. Sediment size ranges from fine silt to coarse boulders, and particle size influences how easily sediment is transported and where it is deposited.

海岸沉积物来源多样：河流输沙、悬崖侵蚀、波浪改造的近海沉积物、如贝壳碎片和珊瑚碎屑等生物物质，以及某些地区来自更新世冰期的冰碛物。沉积物粒径范围从细粉砂到粗砾石，颗粒大小影响其被搬运的难易程度以及沉积的位置。

A sediment budget is the balance between sediment inputs and outputs within a defined coastal cell. When inputs exceed outputs, the coastline accretes; when outputs exceed inputs, erosion dominates. Human interventions, such as dam construction on rivers or dredging of offshore sand, can drastically alter local sediment budgets and trigger coastal retreat far from the original site of disturbance.

沉积物收支是某一特定海岸单元内沉积物输入与输出之间的平衡。当输入超过输出时，海岸线淤积延伸；当输出超过输入时，侵蚀占主导。人类干预，如河流上修建大坝或近海采沙，可能大幅改变局部沉积物收支，并在远离原始干扰地点的地方引发海岸后退。

5. Marine Erosion Processes | 海洋侵蚀作用过程

Erosion of coasts occurs through several distinct mechanisms. Hydraulic action involves the compression of air in cracks, joints, and crevices as waves break, generating intense pressure that fractures rock. Wave quarrying, also termed fluting, is the direct removal of blocks and fragments by the force of the wave itself. Abrasion (corrasion) is the grinding of rock by sediment carried in the water. Solution (corrosion) dissolves soluble minerals, notably limestone and chalk, through chemical reactions with seawater. Attrition is the collision of rock particles with one another, reducing their size and rounding their shape.

海岸侵蚀通过几种不同的机制发生。水力作用是指波浪破碎时，裂缝、节理和裂隙中的空气被压缩，产生强大压力使岩石破裂。波浪采掘（也称浪蚀）是波浪本身的力量直接剥除岩块和碎屑。磨蚀是水中携带的沉积物对岩石的研磨作用。溶蚀是海水与可溶性矿物（尤其是石灰岩和白垩）发生化学反应而将其溶解。磨损则是岩块相互碰撞，使颗粒变小、形状变圆。

Erosion processes = Hydraulic action + Wave quarrying + Abrasion + Solution + Attrition

侵蚀过程 = 水力作用 + 波浪采掘 + 磨蚀 + 溶蚀 + 磨损

Structural weaknesses, such as bedding planes, faults, and joints, control the rate and pattern of erosion. Resistant rocks such as granite create steep cliffs, while weaker rocks such as clay form gentle slopes or actively retreating cliffs.

层理面、断层和节理等结构性薄弱面控制着侵蚀的速度和方式。花岗岩等坚硬岩石形成陡峭悬崖，而黏土等软弱岩石则形成缓坡或持续后退的悬崖。

6. Erosional Landforms: Cliffs, Wave-Cut Platforms, Caves, Arches, and Stacks | 侵蚀地貌：悬崖、浪蚀台地、洞穴、拱门与海蚀柱

Cliffs are steep slopes formed by wave attack at their base, undercutting the rock and causing collapse through mass movement. They retreat landwards over time, leaving behind a gently sloping wave-cut platform at their base. The platform is wider where the rock is weak or tides have a large range. Micro-erosion features such as potholes and rock pools develop on the platform surface.

悬崖是波浪在坡脚冲击侵蚀、掏空岩石并引发块体运动崩塌而形成的陡坡。悬崖随时间向陆地方向后退，在其基部留下一个平缓倾斜的浪蚀台地。岩石软弱或潮差大的地区台地更宽。台地表面常发育壶穴和岩池等微侵蚀地貌。

On headlands with alternating bands of resistant and weak rock, differential erosion produces caves, arches, and stacks. Waves exploit joints to form caves; continued erosion may cut through a headland to form an arch; the roof of an arch eventually collapses, leaving a stack; further erosion reduces the stack to a stump. Emerging forms of erosion such as blowholes and geos (narrow inlets) are also characteristic of rocky coasts.

在具有坚硬与软弱岩层交替的海岬上，差异侵蚀形成洞穴、拱门和海蚀柱。波浪沿节理侵蚀形成洞穴；持续侵蚀可能穿透海岬形成拱门；拱顶最终坍塌，留下海蚀柱；进一步侵蚀将海蚀柱削减为岩桩。此外，吹蚀洞和狭长海湾也是岩石海岸的特征。

7. Marine Deposition Processes and Landforms | 海洋沉积作用与地貌

Deposition occurs when wave energy diminishes, sediment supply is abundant, or frictional drag over the seabed increases. The finest sediments are carried farthest offshore or into sheltered bays, while coarser material is deposited near the shoreline. Depositional landforms include beaches, spits, bars, tombolos, and barrier islands.

当波能减弱、沉积物供应充足或海底摩擦阻力增大时，沉积作用发生。最细的沉积物被搬运到最远的近海区域或隐蔽的海湾中，而较粗的物质则沉积在海岸附近。沉积地貌包括海滩、沙嘴、沙坝、陆连岛和障壁岛。

Beaches are accumulations of sand and shingle that extend from the low-water mark to the limit of storm swash. They have distinct zones: the foreshore, the backshore, and the berm (a flat ridge marking the highest point of normal wave action). During storm conditions, sediment is moved offshore to form a storm bar; during calm weather, gentle waves return sand landwards, rebuilding the beach profile.

海滩是从低潮线延伸到风暴激浪极限的砂和砾石的堆积体。海滩具有明显的分带：前滨、后滨和滩肩（滩肩是正常波浪作用最高点处的平坦脊状地形）。风暴期间，沉积物被搬运到近海形成风暴坝；天气平静时，温和的波浪将沙子带回陆地方向，重建海滩剖面。

Longshore drift is the net movement of sediment along the coast, caused by waves approaching at an angle and receding perpendicularly. This process builds spits across estuaries and bays, often with a recurved end where wind or tidal currents modify the shape.

沿岸漂移是沉积物沿海岸线的净搬运过程，其原因是波浪以斜角接近海岸而垂直于海岸退去。这一过程在河口和海湾中形成沙嘴，其末端常因风或潮汐流的改造而弯曲。

8. Coastal Dunes and Salt Marshes | 海岸沙丘与盐沼

Coastal dunes are aeolian landforms that develop where sand is available, winds are strong, and vegetation can colonise the backshore. Embryo dunes form first, followed by foredunes (yellow dunes) and then grey dunes as organic matter accumulates and soil develops. Key conditions for dune formation include a wide beach at low tide, onshore winds, and pioneer species capable of trapping sand, such as marram grass.

海岸沙丘是风成地貌，在沙子充足、风力强劲且后滨有植被定居的条件下发育。首先形成雏形沙丘，随后是前沙丘（黄沙丘），随着有机质积累和成壤作用的发展，演变为灰沙丘。沙丘形成的关键条件包括低潮时宽阔的海滩、向岸风以及能够固定沙粒的先锋物种，如滨草。

Salt marshes are vegetated intertidal zones in sheltered estuaries and behind spits. They trap fine sediment carried by tidal currents, and as sediment accumulates, the marsh surface rises, allowing less frequent inundation and the establishment of more diverse plant communities. Salt marshes are among the most productive ecosystems on Earth and provide crucial habitats for birds and juvenile fish.

盐沼是在隐蔽河口和沙嘴后方的有植被覆盖的潮间带区域。它们捕获潮汐流携带的细粒沉积物；随着沉积物不断堆积，沼泽表面抬升，被淹没的频率降低，从而能建立更多样化的植物群落。盐沼是地球上生产力最高的生态系统之一，为鸟类和幼鱼提供重要栖息地。

9. Sea-Level Change and Its Geomorphic Consequences | 海平面变化及其地貌后果

Eustatic sea-level change is global and is caused by changes in the volume of water in the oceans or the capacity of ocean basins. Isostatic change is regional and results from vertical movements of the land, such as post-glacial rebound or subsidence due to sediment loading. During the last glacial maximum approximately 20,000 years ago, sea level was over 120 metres lower than today.

全球性海平面变化（水动型）是由海洋水量或洋盆容积的变化引起的全球现象。均衡型海平面变化则是区域性的，由地壳垂直运动引起，如冰后回弹或因沉积物负载造成的地面沉降。在约20,000年前的末次冰盛期，海平面比今天低120米以上。

Submergent coastlines, such as rias and fjords, result from rising sea levels relatively to the land. Emergent coastlines, such as raised beaches and marine terraces, indicate uplift or falling sea levels. These features are valuable evidence for reconstructing former sea levels and understanding tectonic processes.

溺谷和峡湾等溺没型海岸是海面相对陆地上升的结果。上升海滩和海成阶地等升露型海岸则表明地壳抬升或海面下降。这些地貌特征为重建古海平面和理解构造过程提供了宝贵证据。

10. Human Impacts and Coastal Management | 人类影响与海岸管理

Humans have fundamentally altered coastal sediment budgets through urbanisation, river management, mining of sand, and construction of coastal defences. Hard engineering measures such as sea walls, groynes, and rock armour provide short-term protection but often exacerbate erosion down-drift by interrupting sediment supply. Soft engineering approaches, including beach nourishment, dune re-profiling, and habitat restoration, are increasingly favoured for their lower environmental impact and greater adaptability to climate change.

人类通过城市化、河流管理、采沙和海岸防护工程建设极大地改变了海岸沉积物收支。海堤、丁坝和抛石护岸等硬性工程措施提供了短期保护，但往往因阻断沉积物供应而加剧了背风侧的侵蚀。海滩补沙、沙丘修整和栖息地修复等软性工程方案因其较低的环境影响和更强的气候变化适应性而日益受到青睐。

Any effective coastal management must adopt an integrated and sustainable approach. Sediment cells, which define natural boundaries for sediment movement, should form the framework for planning decisions. Shoreline Management Plans in the UK, for example, assess risk, set policies for erosion and flood management over different epochs, and balance economic, social, and environmental considerations.

任何有效的海岸管理都必须采取综合和可持续的方式。沉积物单元界定了沉积物运移的自然边界，应作为规划决策的框架。英国的海岸线管理计划便以不同时期内的侵蚀和洪水管理政策、风险评估为基础，综合考虑经济、社会和环境因素。

11. Fieldwork and Data Analysis in Coastal Studies | 海岸研究中的野外调查与数据分析

Coastal fieldwork commonly involves measuring beach profiles, sediment size and shape, rates of longshore drift, and vegetation zonation. Techniques include using a clinometer and ranging poles to measure slopes, sieving and pebble shape analysis to classify sediment, and deploying tracers (such as fluorescent sand) to track sediment movement.

海岸野外考察通常涉及测量海滩剖面、沉积物粒径和形态、沿岸漂移速率以及植被分带。常用技术包括使用测斜仪和标尺测量坡度、用筛分法和砾石形状分析来分类沉积物，以及投放荧光示踪沙来追踪沉积物的运移。

This empirical evidence is used by geographers to build models of coastal behaviour, to test hypotheses about the processes operating at a site, and to evaluate the effectiveness of management strategies. Advances such as LiDAR, drone-based photogrammetry, and GIS now enable high-resolution monitoring of coastal change over both short and long timescales.

地理学家利用这些经验证据构建海岸行为模型、检验关于某一地点作用过程的假设，并评估管理策略的有效性。LiDAR技术、无人机摄影测量和GIS等新兴技术如今能够对海岸变化进行短、长时间尺度的高分辨率监测。

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Coastal Systems and Processes | 海岸环境系统与作用过程