阐述并讨论了近年来海岸侵蚀与管理的相关理论和方法,探讨了我国海岸侵蚀管理现状和发展方向。描述了沙丘、软岩海岸以及淤泥质海岸等的侵蚀机理,指出海岸侵蚀主要由河流入海泥沙减少、海岸工程拦沙、采砂和围垦、相对海平面上升、海岸带生态系统破坏和护岸工程弱化等原因引起,并讨论了海岸侵蚀的危害；根据我国海岸侵蚀特点把海岸侵蚀分成沙质海岸侵蚀、软岩海岸侵蚀、淤泥质海岸侵蚀、生物海岸侵蚀和海岸工程侵蚀5类,提出了海岸侵蚀分类管理的方法。补充发展了我国海岸侵蚀理论,为海岸侵蚀管理利益相关者提供参考。
Coastal erosion and management attract much conern all around the world as coastal erosion is a problem at many coastal sites exacerbated by human activities and its adaptability through reasonable mitigation measures. This paper summarizes the main factors causing coastal erosion including reduction of sediment discharged by rivers trapped coastal structures, sand mining and reclaimation, relative sea-level rise, destruction of coastal ecosystem and weakening of coastal defenses. Mechanisms causing erosion of coastal dune, soft rock coast and muddy coast are identified and discussed. Sandy coastal erosion, soft rock coastal erosion, muddy coastal erosion, biological coastal erosion and coastal structural erosion are identified according to the characteristics of erosion in China. This study supplements the theory and methodology for coastal erosion management and provides information for managers and stakeholders.
2.1.1 Bruun法则
式中：L-为剖面横向长度,B-为滩肩高,h-为闭合深度,S-为海平面上升量。
2.1.2 风暴引起的沙丘侵蚀
2.1.3 软岩海岸的侵蚀
基岩海岸的侵蚀后退主要受风暴特征和岩石的稳定性控制,两者互为条件,当岩石稳定性被破坏到很低时,很小的风暴级别就可以触发滑塌；相反,很大的风暴级别对稳定性强的基岩海岸可能造成的影响极小。这就说明在预测软岩海岸侵蚀风险时,一定要综合多方面的因素才有可能得出可信的结果。
2.1.4 粉砂淤泥质海岸的侵蚀
近年来对粉砂淤泥质海岸侵蚀的研究方兴未艾,主要关注侵蚀的原因、机制等,但研究区域相对分散,得出的结论不具有普适性。不同海陆相互作用环境的海岸侵蚀机制迥异,淤泥质海岸的侵蚀过程还需要进一步的实地考察与试验研究。
2.2.1 海岸侵蚀的原因
2.2.2 海岸侵蚀的危害
2.3.1 入海河流输沙减少
此外,由于城市建设用砂,人为大量采砂是构成海岸泥沙亏损的另一重要原因。虽然近年来岸滩采砂有所减少,但日益加重的河床采砂同样会引起海岸侵蚀。
2.3.2 海平面上升
根据以上对影响中国海岸侵蚀主要原因的论述可知,我国未来海岸侵蚀将持续并有加剧的趋势,特别是受入海泥沙供给和海平面上升影响敏感的滨海三角洲平原地区。另外,海岸工程拦沙以及海岸生态系统破坏对局部地区海岸侵蚀的影响逐渐突出,对已退化的生态系统的修复重建任重道远。
借鉴自然灾害和地质灾害风险评估的理论和方法,综合国内外海岸侵蚀评价研究成果,本文认为海岸侵蚀风险评价应有以下含义：①是对特定区域未来一段时间内海岸侵蚀可能造成的潜在损失的分析评定过程；②评价内容包括地质环境危险性和社会经济易损性,前者涉及致灾因素,由显形侵蚀危险性和隐形侵蚀危险性构成,后者针对承灾体,由暴露性和综合减灾能力构成；③评价结果以相对风险级别的形式表达,并对风险排序,制作风险区划图；④指导风险管理,对于高风险区优先实施风险转移减少风险损失。
海岸监测为海岸系统演变提供重要的信息,是海岸侵蚀研究和管理不可或缺的第一手资料。岸滩形变测量的新技术从早期采用经纬仪发展到红外测距、全站仪以及目前比较流行的RTKGPS。水下测量从早期的铅砣测深到现在广泛应用的回声探测仪技术,取得了革命性的进展。近年来测量技术得到迅速发展,新的监测设备和技术广泛应用,如机载激光测高技术、Argus重复摄像系统等,为人们方便快捷的提供更多的更可靠的信息,成为未来海岸测量技术发展的方向。
根据我国海岸侵蚀的机理与原因不同,海岸侵蚀可以划分为以下5种类型：①砂砾质海岸侵蚀；②软岩海岸侵蚀；③淤泥质海岸侵蚀；④生物海岸侵蚀；⑤海岸工程侵蚀。海岸侵蚀类型主要受地质构造、气候条件以及人类活动的影响,图5描述了中国不海岸侵蚀类型的分布特征。对于不同的海岸侵蚀类型,根据实地考察和理论论证应采取不同的海岸侵蚀防护措施,下面分类阐述。
3.4.1 砂质海岸侵蚀防护
砂质海岸侵蚀主要表现为沙丘侵蚀形成侵蚀陡坎,或滩肩侵蚀变窄、滩面沉积物粗化,导致海滩质量下降。目前人们较为接受的沙质海岸侵蚀的防护措施有沙丘或滩肩补沙、防护林护沙或设置缓冲区禁止采砂和人为干预等。
3.4.2 软岩海岸侵蚀防护
3.4.3 淤泥质海岸侵蚀防护
生物护滩的缺点是易遭到破坏,一旦植被破坏侵蚀又会发生；另外,还需考虑物种入侵的危险。最佳的淤泥质海岸侵蚀防护措施是建设护岸工程的同时,应充分考察当地的地质环境、海洋环境特点,并适宜的配合生物护滩,一方面减少了海洋动力对海堤的冲蚀破坏,同时生物作用又能促淤造滩。
3.4.4 生物海岸侵蚀防护
生物海岸侵蚀的防治应以适应性措施为主,主要是建立自然保护区,红树林及珊瑚礁的生态修复与重建以及人工引种种植也是有效的防护措施。
生物海岸的修复与重建应关注以下几点：①修复重建区的选择,选择适宜红树林或珊瑚生长的区域,如遭受破坏的湿地原地修复或历史上移植引种成功海岸重建；②加强修复重建区的维护管理,防止二次破坏。③广泛开展相关教育及实践活动,增强人们的保护意识。
3.4.5 海岸工程侵蚀防护
海岸工程引起的海岸侵蚀存在于海岸工程临近区域,一般出现在紧邻工程的下游方向,造成岸线侵蚀后退,如导堤、丁坝、防波堤等护岸工程均能引起下游岸线的侵蚀；海堤等护岸工程不但截断了海滩陆源沉积物供应而且加强了海浪的冲刷侵蚀,最终导致严重的滩面下蚀,护岸失稳破坏。
海岸工程侵蚀应从源头防治,从工程规划建设初期就应当权衡利弊充分考虑可能造成的侵蚀及其防治措施；对于严重破坏的护岸更换替代工程,如软结构护滩工程或适应性措施。对于工程下游岸线后退,目前较为流行的措施是补沙或旁侧输沙,即利用上游淤积的泥沙或航道疏浚泥沙就近进行海滩人工养护,减少异地沙源的经济费用。对于滩面下蚀,一般是适时进行海滩养护,既能减轻波浪对护岸的破坏又能创造宽阔的海滩供休闲旅游。
(1)根据泥沙供给变化和沿岸水动力特征把海岸侵蚀的主要原因归为以下几类：①河流入海泥沙减少；②海岸工程拦沙；③采砂和围垦；④相对海平面上升；⑤海岸带生态系统破坏；⑥护岸工程弱化。
(2)海岸侵蚀的危害可以概括为以下3个方面：①海岸带土地流失,丧失了海岸带原有的经济、社会和生态价值；②风暴引起的显形侵蚀摧毁天然海岸防护,造成河口或海岸低洼地的淹没、破坏海岸生态体统以及造成土壤的盐碱化等；③岸滩下蚀破坏人工海岸防护,加快了海岸侵蚀的过程或引起沿岸洪泛。
(3)我国未来海岸侵蚀将持续并有加剧的趋势,特别是受入海泥沙供给和海平面上升影响敏感的滨海三角洲平原地区。另外,海岸工程拦沙以及海岸生态系统破坏对局部地区海岸侵蚀的影响逐渐突出,对已退化的生态系统的修复重建任重道远。
(4)海岸侵蚀风险评价含义：①对特定区域未来一段时间内海岸侵蚀可能造成的潜在损失的分析评定过程；②评价内容包括地质环境危险性和社会经济易损性,前者涉及致灾因素,由显形侵蚀危险性和隐形侵蚀危险性构成,后者针对承灾体,由暴露性和综合减灾能力构成；③评价结果以相对风险级别的形式表达,并对风险排序,制作风险区划图；④指导风险管理,对于高风险区优先实施风险转移减少风险损失。
(5)根据我国海岸侵蚀的机理与原因不同,海岸侵蚀可以划分为以下5种类型：①砂砾质海岸侵蚀；②软岩海岸侵蚀；③淤泥质海岸侵蚀；④生物海岸侵蚀；⑤海岸工程侵蚀。不同的海岸侵蚀类型采取不同的海岸侵蚀防护措施,砂砾质海岸侵蚀应以护滩工程为主,辅以护岸工程；软岩海岸侵蚀以护岸工程防护为主；淤泥质海岸侵蚀应以护岸工程为主,辅以护滩工程；亚热带热带的生物海岸侵蚀则以适应性工程适宜；海岸工程侵蚀是一类特殊的海岸侵蚀类型,对于这类海岸侵蚀应以源头治理为主,即要禁止不合理的海岸工程建设,同时对已存在工程造成的侵蚀加强防治。
Coastal erosion is a problem at many coastal sites caused by natural effects as well as human activities. This paper explores the coastal cell concept to deal with coastal erosion by identifying and analysingthe sediment volumes accumulated in large-scale and small-scale coastal cells at various sites. Mechanisms causing chronic erosion and episodic erosion related to coastal variability are identified and discussed. The effectiveness of soft and hard remedial measures for sandy beaches are assessed based on laboratory, field and modelling experiences.
? Coastal erosion has always existed, but it is now largely intensified by human activities. ? Massive sand nourishment is an attractive solution of coastal erosion in terms of coastal safety and natural values, but it may not be the most economic solution. ? Hard structures such as groynes and breakwaters are no remedy for dune erosion during storm conditions with high surge levels. ? Hard structures may lead to an increase of coastal variability with maximum recession rates much larger than the initial shoreline recession. ? Detailed mathematical models are now available to determine with sufficient accuracy the morphological impact of various hard structures.
This paper presents results of experimental and mathematical modelling of beach and dune erosion under storm events. Re-analysis of the experimental results on dune erosion in small-scale and large-scale flumes shows that the dune erosion for extreme conditions is somewhat smaller than that based on earlier analysis results.
Dune erosion caused by wave impact has been modelled by a cross-shore profile model (CROSMOR-model), which is based on a ‘wave by wave’ modelling approach solving the wave energy equation for each individual wave. The model has been applied to the recent Deltaflume experiments on dune erosion. The three main processes affecting dune erosion have been taken into account: the generation of low-frequency effects, the production of extra turbulence due to wave breaking and wave collision and the sliding of the dune face due to wave impact. The calibrated model can very well simulate the observed dune erosion above the storm surge level during storm events in small-scale facilities, large-scale facilities and in the protoype (1953 storm in The Netherlands) using the same model settings. The mathematical model results have been used to develop a new simplified dune erosion rule.
The morphological and ecological response of tidal flat and coastal wetlands to sea level rise is one of the basic aspects of the impacts of global warming on coastal zones. Jiangsu coastal plain, located in the middle of China's coastal area, is the vastest area with most diversiform ecological types of mud flat in China, even all over the world. Therefore, research on the morphological response of mud flat to sea level change in this area undoubtedly is typical and of global significance. Based on the 112 times of field elevation measurements to 19 typical sections since 1980, using statistic methods, the morphological response of typical accretion and erosion section of mud flat to sea level rise was discussed in this paper. The estimated results show that, there are good correlations between accretion rate (both the horizontal and the vertical) of mud flat and sea level change in the study area, just the correlation is diverse in different sections or different parts of the same section due to the various distributions of current velocity and silt flux. The general tendency of the response of mud flat to sea level rise is that the accretion will tend to slow down and erosion will tend to be intensified. To typical accretion section, when sea level rises, the parts of mud flat above mean tidal line will still accrete, but the accretion rate will decrease except the part around mean high tidal line, the speediest rate of accretion occurs in the part between mean high tidal line and that one of the neaps. Whereas, the parts below mean tidal line will experience more intense erosion. The convex profile of mud flat will become more and more steeper and curving due to the upper side accreting and the down side eroding. To typical erosion section, the response of mud flat profile to sea level rise will present a opposite trend. The parts above mean tidal line will be eroded intensively, but the parts below mean tidal line will accrete. The concave profile will become more and more straight.
通过对江苏滨海平原淤泥质潮滩1980年以来19个固定潮滩断面112个测次滩面高程测量的统计分析, 探讨典型淤泥质潮滩剖面形态对海平面变化的形态响应过程。结果表明, 典型淤涨岸段海平面上升, 多年平均潮位线以上滩面仍将淤积加高, 但淤高幅度除多年平均高潮线附近滩面相对较大外, 其余均较小, 表明随海平面上升该滩带总体淤积速率将趋于减小; 与此相反, 多年平均潮位线以下滩面则趋于蚀低, 且侵蚀强度较大, 表明该滩带的侵蚀有加剧趋向, 最终滩面总体形态将因上带不断淤高和下带不断蚀低而逐渐变陡,剖面上凸形态的曲率不断加大。 典型侵蚀岸段, 海平面上升的效应则相反, 海平面上升, 多年平均潮位线以上滩面强烈蚀低; 而多年平均潮位线以下滩面则强烈淤积加高, 剖面的上凹形态最终将因上带不断蚀低和下带不断淤高而趋于平直。
The Netherlands is a low-lying country, in which 9 million people are living below sea level and 70% of the gross domestic product is being earned in areas below sea level. Therefore, protection against flooding is traditionally the primary focus of coastal policy in the Netherlands. Analysis shows that characteristics of Dutch coastal management very well comply with the recommendations and key concepts to support sustainable coastal management as issued by the EU in 2004 (EUROSION). Sediment management represents the core of erosion management in the Netherlands; key concepts like resilience, coastal sediment cells, favorable sediment status and strategic sediment reservoirs, are important building stones. Development and implementation of coastal erosion management in the Netherlands, has implicitly been guided by a systematic Frame-of-Reference. Characteristics of this approach are the definition of clear objectives at different levels (i.e. strategic, tactical and operational) and an operational decision recipe related to policy development and implementation. Application of the Frame-of-Reference to current problems and challenges in Dutch coastal management indicates its ability to reveal shortcomings of the existing approach, and to explore potential solutions. Where EUROSION offers important concepts to define coastal erosion management, the Frame-of-Reference offers a tool to discern different objectives and responsibilities. The combination of both strongly supports implementation of coastal erosion management.
? We show that Dutch coastal policy is characterized by objectives at 3 scale levels. ? Sediment management is the core of erosion management, defined by 4 key concepts. ? Resilience, sediment cells, favorable sediment status and strategic reservoirs. ? Development and implementation is guided by a systematic Frame-of-Reference. ? A tool to discern different objectives and responsibilities.