, 黄德全Preliminary observation of morphological responses totyphoon of coastal dunes
DONGYuxiang, HUANGDequan收稿日期:2016-05-6
修回日期:2016-08-3
网络出版日期:2016-10-26
版权声明:2016《地理研究》编辑部《地理研究》编辑部
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1 引言
海岸沙丘形成于海、陆、气三相间交互作用在20世纪80年代获得共识后[1,2],台风与海岸风沙地貌形成及演化的相互关系受到关注[3-5]。美国、加拿大、墨西哥、英国、法国、葡萄牙、丹麦和波兰等开展了海岸沙丘对台风（风暴或飓风）响应的相关研究[6-20],其中尤以海岸沙丘形态变化对台风响应研究居多,如Pries等通过飓风前后不同沙丘类型的面积、分布位置及其形态数据的比较,分析研究了飓风对墨西哥湾Santa Rosa岛海岸沙丘的侵蚀[14];Serge Suanez等对法国Vougot海岸不同类型沙丘在风暴后的恢复及其差异进行了研究[10];Claudino-Sales等认为飓风中海岸沙丘对风暴响应的差异主要受制于飓风的强度、持续性和频率以及包括海岸沙地宽度和高度、植被类型、沙丘距海岸线距离和沙地连续性等因子的综合作用[6]。但就风暴或飓风对海岸沙丘形态的影响及其机理,****观点不一。Morton等认为风暴强度对海岸沙丘形态具有重要影响[15];Furmanczyk等利用1978-2009年32次风暴数据,分析了风暴参数与南波罗的海海岸沙丘侵蚀量间的数量关系[13,16];Pye等通过对近50年英格兰西北Sefton海岸前丘蚀积数据的分析,提出影响其变化的主要原因是风暴频率与规模及其引起的高潮位的变化[9];Houser等在分析了2005年卡特琳娜飓风后佛罗里达典型海岸沙丘的恢复情况后也认为飓风对海岸沙丘的作用及其恢复主要取决于飓风的频率[17]。上述研究中,高分辨率、可实时观测的仪器设备的应用促进了研究的发展,研究手段也就由传统的借助经纬仪和平板仪的地形测量与遥感影像分析[7,21],发展到全站仪测量及激光雷达（LIDAR）、RTK GPS测量、立体摄影和三维激光扫描等新技术的应用[22-24],就为研究海岸沙丘形态的台风响应提供了必要且可靠的高精度、高时空分辨率数据。相比而言,国内将海岸沙丘与波浪、海滩联系起来进行波浪—海滩—沙丘相互作用综合研究尚处于起步阶段[25],故有关台风对海岸沙丘形态影响与作用的研究近乎空白,仅有个别海滩台风效应研究中因把海岸沙丘当作沙质海滩组成部分而在研究中有涉及[26-28]。为此,选择深受台风影响且是中国海岸风沙地貌典型分布区的福建省平潭岛[29-33],进行台风登陆前后海岸沙丘形态变化的高精度、大样本数据采集,分析不同类型海岸沙丘形态对台风的响应特征,可以填补国内研究空白,阐明中国海岸风沙地貌形态的台风响应机理,建立中国海岸沙丘形态变化的台风响应模式。2 研究区概况与研究方法
2.1 研究区概况
平潭岛为地处福建东部海域的全国第五大岛（图1）,其海岸线中近100 km为沙质海岸,岛上风沙地面积达8685 hm2[34],发育了形态典型的冢形前丘、海岸前丘、横向沙丘、海岸沙席和爬坡沙丘等海岸沙丘[34-37],是中国海岸沙丘类型较多、形态比较典型、面积较大且因早期交通不便人为干扰相对较小的海岸风沙地貌典型分布区域[29-31]。平潭岛属南亚热带湿润气候但相对少雨和多风。1981-2010年间年均气温19.9℃,年均降雨量1250.1 mm,年均蒸发量1164.9 mm,年均风速高达4.5 m/s;受台风影响最大风速为25.0 m/s,期间台风影响平潭98次,一般每年2~5次,多出现在7-9月,常引发10 m/s以上大风和风暴潮,对海岸沙丘形态塑造具有重要影响。基于上述平潭岛海岸沙丘的典型性和受台风影响的代表性,选择平潭岛进行海岸沙丘形态对台风响应的观测与研究。
显示原图|下载原图ZIP|生成PPT图1研究区观测点位置图及沙丘景观
-->Fig. 1Distribution map of field observation locations in the research area and their geomorphic landscape pictures
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2014年第10号热带风暴“麦德姆”（Typhoon Matmo）于2014年7月18日2时在西北太平洋面上生成,在台湾省台东县长滨乡沿海登陆后又于7月23日15时30分在福建省福清市高山镇沿海登陆,登陆时中心附近最大风力为11级（强热带风暴级,30 m/s）、中心最低气压980 hPa。台风“麦德姆”登陆地点距平潭岛最近距离不足30 km,对平潭海岸风沙地貌的影响与作用显著,可为观测和认识海岸沙丘形态对台风响应的典型案例。
2.2 研究方法
选择在平潭岛海岸的四个典型海岸沙丘分布区设立野外定位观测点,即位于平潭岛东南部的白鸽屿后、东北部的白犬山、北部的芦洋农场和南部的仙岐宫附近海岸（图1）,分别是海岸前丘、爬坡沙丘、横向沙丘和海岸沙席等海岸沙丘类型的典型分布地点。通过台风“麦德姆”登陆前后各个观测点上海岸沙丘形态的高精度测量数据对比,分析研究区不同类型海岸沙丘形态对台风的响应特征。具体是在每个定位观测点上选择其海岸沙丘典型地段设立观测样区（图2）,观测样区根据海岸沙丘形态自海向陆横断沙丘设置,在样区内综合考虑测点的均匀性和海岸沙丘形态部位的典型性具体设立高程测点,其中在白鸽屿后、白犬山、芦洋和仙岐宫四个观测点样区内分别设立了313个、200个、204个和214个定位测量点位（图2）。另外,为更好分析海岸沙丘形态的变化,还在每个观测样区内设立四条或三条分析样带（图2）,通过样带上测点数据的变化反映海岸沙丘断面上典型部位的高程变化。
显示原图|下载原图ZIP|生成PPT图2观测样区的高程测点和样带
-->Fig. 2Height surveying points and belts over coastal dunes in observation sample areas
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测点数据采集采用多站差分RTKGPS技术方法。采用多站差分RTKGPS技术求解坐标平滑参数及利用曲面拟合求解高程异常的方法,对海岸沙丘形态的测量精度可达到厘米甚至毫米级[38],该测量技术应可满足海岸沙丘形态变化测量的精度要求,并已成功应用于海岸沙丘相关研究中[39,40],故采用该技术进行台风“麦德姆”登陆前后海岸沙丘形态变化的高精度测量。具体是分别在平潭岛的四个观测点进行多点位尤其是海岸沙丘典型部位如迎风坡坡脚和沙丘丘顶等点位高程的定位测量,应用RTKGPS精确的导航功能,在台风前后分别按所设测点的点位进行重复测量,具体获取台风“麦德姆”登陆前2014年7月15-17日和登陆后2014年9月4-7日的测点高程数据,以此分析海岸沙丘在台风“麦德姆”登陆前后的形态变化。其中,台风“麦德姆”登陆后的测量时间稍迟,但因该时段为少风和植被繁茂季节,同时亦未受其他台风影响,海岸沙丘形态受其他因素影响的变化较小,故两次测量数据应可以代表台风对海岸沙丘形态的影响与作用。
3 结果分析
根据台风“麦德姆”登陆前后平潭岛四个观测点上931个海岸沙丘形态定位测点的高程精确测量结果,可明确研究区内典型海岸沙丘整体、样带及沙丘不同部位的变化情况。3.1 观测点白鸽屿后的海岸前丘
白鸽屿后海岸是由多个草（灌）丛沙丘组合而成的海岸前丘复合体（图2a）,其313个测点中有22个因潮水淹没无数据,其余291个测点数据的变化表明,整个观测样区内海岸沙丘体积在台风“麦德姆”登陆后由96541.7 m3减小为94414.4 m3,291个测点高程的平均变化值为0.33 m,除6个测点高程没有变化外,测点高程降低幅度大于升高幅度,有128个测点的高程降低,平均降低幅度为0.35 m,最大降低值为2.45 m;有157个测点的高程升高,平均升高幅度为0.32 m,升高最大值为1.87 m。样区内四个样带上测点的高程平均变化值介于0.32~0.39 m,高程升高与降低幅度各有不同,但样带上不同部位高程变化相对较为一致,一般是海滩与海岸前丘迎风坡脚及坡中高程增加、丘顶高度降低、背风坡坡脚高程不变或减小,如样带A上海滩与海岸前丘迎风坡坡脚高程增加0.05 m和0.18 m、丘顶高度降低0.18 m和背风坡坡脚高程不变（表1）,但其中样带D的丘顶高度稍有增加升高了0.07 m。Tab. 1
表1
表1海岸沙丘不同部位的高程变化（m）
Tab. 1Height change of geomorphic sites at the surveying belts over different types of coastal dunes
| 样区与样带 | 海滩和海岸沙丘部位 | |||||
|---|---|---|---|---|---|---|
| 海岸前丘 | 地貌部位 | 海滩 | 迎风坡脚 | 迎风坡坡中 | 沙丘丘顶 | 背风坡脚 |
| 样带A | +0.05 | +0.18 | +0.09 | -0.18 | 0.00 | |
| 样带均值 | +0.06 | +0.25 | +0.04 | -0.28 | -0.03 | |
| 爬坡沙丘 | 地貌部位 | 沙丘前缘坡脚 | 沙丘前缘坡中 | 沙丘前缘顶部 | 沙丘中部 | 沙丘后缘 |
| 样带A | -0.22 | -0.63 | -0.17 | -0.18 | -0.23 | |
| 样带均值 | -0.24 | -0.43 | -0.10 | -0.16 | -0.24 | |
| 横向沙丘 | 地貌部位 | 迎风坡脚 | 迎风坡坡中 | 沙丘丘顶 | 背风坡中部 | 背风坡坡脚 |
| 样带A | +0.05 | -0.17 | -1.43 | -0.41 | +0.32 | |
| 样带均值 | 0.00 | -0.06 | -0.38 | -0.06 | -0.04 | |
| 海岸沙席 | 地貌部位 | 海滩 | 沙席前缘 | 沙席中部 | 沙席后缘 | |
| 样带A | -0.15 | -0.02 | +0.04 | +0.58 | ||
| 样带均值 | -0.14 | -0.03 | +0.04 | +0.22 | ||
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3.2 观测点白犬山的爬坡沙丘
白犬山附近海岸的爬坡沙丘（图2b）,观测样区爬坡沙丘体积在台风“麦德姆”登陆前后分别为40110.2 m3和39328.1 m3,减小了782.1 m3,样区内200个测点高程变化的平均值为0.21 m,高程最大变化值为1.06 m,样区内测点高程明显降低,其中除1个测点高程没有变化外,仅有16个测点的高程升高,平均升高0.16 m,最大升高值0.58 m;其余183个测点的高程降低,平均降低幅度为0.21 m,高程降低最大值为1.06 m。四个样带上测点的平均高程变化值为0.17~0.25 m,高程降低测点数占绝对优势且降低值明显大于升高值,同时不同部位的高程变化相对较为一致（表1）,基本上爬坡沙丘前缘迎风坡坡脚高程有所降低,至迎风坡中部高程降低程度加大至最大,在爬坡沙丘前缘顶部变化幅度降低,之后高程降低程度会有所增加直至爬坡沙丘后缘。3.3 观测点芦洋农场的横向沙丘
芦洋农场观测点为典型横向沙丘（图2c）,样区海岸横向沙丘体积在台风后有所减小,由26675.8 m3减至26523.7 m3,样区内204个测点高程的平均变化值为0.18 m,最大变化值为1.45 m,测点高程升高幅度小于降低,其中有108个测点的高程升高,平均升高0.15 m,最大升高值为1.45 m;其余96个测点的高程降低,平均降低幅度为0.21 m,降低最大值为1.43 m。四个样带上测点高程平均变化值介于0.11~0.28 m,各样带上高程升高与降低的测点数大致相当,但其降低幅度也明显大于升高,同时受台风“麦德姆”影响整体上造成海岸横向沙丘高程的降低,尤其是沙丘丘顶高程普遍降低,如样带A上沙丘丘顶高程降低达1.43 m（表1）,但是不同样带上不同沙丘部位的高程变化略有不同,如迎风坡和背风坡在不同样带上的变化方向和幅度均有差异。3.4 观测点仙岐宫的海岸沙席
仙岐宫海岸观测点为形态典型的海岸沙席（图2d）,整个观测样区海岸沙席体积在台风“麦德姆”登陆后增加1627.8 m3,样区内214个测点高程的平均变化值为0.14 m,高程最大变化值为1.62 m,测点高程升高幅度大于降低,其中除两个测点高程不变外,有117个测点的高程降低,平均降低0.13 m,最大降低值为1.49 m;另有95个测点的高程升高,平均升高幅度为0.16 m,最大升高值为1.62 m。该观测点不同样带上测点高程的变化较为一致,三个样带的高程平均变化值介于0.08~0.16 m,其测点高程升高与降低值较为相近,且各样带上不同部位的高程变化亦大致相同,均为海滩及海岸沙席前缘高程降低,向陆逐步转为高程增加直至沙席后缘（表1）。4 讨论
4.1 形态变化特点
基于台风“麦德姆”登陆前后研究区内四个样区、15个样带和931个测点的观测结果,可概括出海岸沙丘受台风影响的形态变化特点：第一,研究区内海岸沙丘在台风“麦德姆”登陆前后的形态变化明显,四个样区测点高程的平均变化值为0.22 m（表2）,整体而言以体积减小和沙丘高度降低为主,如四个观测样区的海岸沙丘体积在台风登陆后平均减小了358.3 m3,平均减小0.59%,最多的白鸽屿后海岸前丘样区内的体积减小了2.20%（表2）,同时以高程增加减去高程减小后平均计算得到的四个观测样区测点高程变化的平均值为-0.05 m,样区高程增加测点的增加值的均值亦较高程降低测点的降低值的均值低0.03 m。
Tab. 2
表2
表2观测点海岸沙丘体积与高程变化统计
Tab. 2Statistics of volume and height change of coastal dunes at observation locations
| 观测点 | 样区内海岸沙丘体积（m3, %） | 测点高程变化（m） | |||||||
|---|---|---|---|---|---|---|---|---|---|
| 台风前 体积 | 台风后 体积 | 体积 变化量 | 体积 变化率 | 变化值 平均值 | 高程变化 平均值 | 高程升高 均值 | 高程降低 均值 | ||
| 白鸽屿后 | 96541.7 | 94414.4 | -2127.3 | -2.20 | 0.33 | +0.02 | +0.32 | -0.35 | |
| 白犬山 | 40110.2 | 39328.1 | -782.1 | -1.95 | 0.21 | -0.18 | +0.16 | -0.21 | |
| 芦洋 | 26675.3 | 26523.7 | -151.6 | -0.57 | 0.18 | -0.02 | +0.15 | -0.21 | |
| 仙岐宫 | 80663.2 | 82291.0 | +1627.8 | +2.02 | 0.14 | -0.01 | +0.16 | -0.13 | |
| 均值 | 60997.6 | 60639.3 | -358.3 | -0.59 | 0.22 | -0.05 | +0.20 | -0.23 | |
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第二,不同沙丘类型台风登陆前后的形态变化程度及特征并不相同,就体积变化而言海岸前丘、爬坡沙丘和横向沙丘的体积受台风影响以减小为特征,其中尤以海岸前丘样区的体积减小为多,但海岸沙席样区体积增加了2.02%;同样,不同样区高程变化量值亦有差异（表1、表2）,如白鸽屿后四个样带测点的高程升高与降低幅度各有不同,白犬山四个样带上高程降低测点数占绝对优势且降低值明显大于升高值,芦洋农场各样带上高程升高与降低的测点数大致相当但其降低幅度明显大于升高幅度,仙岐宫不同样带测点高程的变化较为一致且测点高程升高与降低值也较为相近,由此充分反映出不同海岸沙丘在台风登陆前后形态变化的差异性。
第三,同一沙丘不同部位的变化并非完全一致（表1、图3）,如白鸽屿后的海岸前丘受台风“麦德姆”影响其迎风坡脚高程增加、丘顶高度降低、背风坡坡脚高程不变或减小,白犬山爬坡沙丘的各个部位均呈现为不同程度的高程降低,芦洋的横向沙丘则以部分迎风坡高程略增和沙丘丘顶高程普遍降低为主,仙岐宫的海岸沙席整体以海岸沙席前缘高程降低、向陆高程逐渐增加至沙席后缘为特点。
显示原图|下载原图ZIP|生成PPT图3海岸沙丘样带上主要测点的高程变化
-->Fig. 3Profiles of height change of main surveying points at the surveying belts over coastal dunes
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4.2 形态响应原因分析
平潭岛海岸沙丘形态在台风“麦德姆”登陆前后的上述变化,说明海岸沙丘对台风的形态响应总体是以强风力侵蚀下的高度降低、体积减小为基本特征,该观测结果与2004飓风“伊万（Ivan）”和2005年飓风“丹尼斯（Dennis）”影响下海岸沙丘形态的变化性质较为一致。如2004年受飓风“伊万（Ivan）”影响Santa Rosa Island的海岸沙丘高度平均降低了0.09 m、St. George Island的海岸沙丘高度有0.3~0.7 m的变化[18,19],2005年受飓风“丹尼斯（Dennis）”影响St. George Island的沙丘体积减小了约7%[20],但既非相关研究所认为的具有响应量与变化性质特征的完全一致性[6-20],更非类似台风这样发生频率较低的大（强）风因其为海岸沙丘供应沙物质而有助于海岸沙丘的发育[2],不同类型海岸沙丘响应的差异性特征较为突出。究其原因,首先,强热带风暴级台风“麦德姆”登陆时,在台风中心风速高达30 m/s强风作用下,台风登陆地点附近平潭岛的风力侵蚀力及其挟沙能力极强,就表现为对海岸沙丘的作用以强烈侵蚀为主,导致对海岸沙丘的普遍侵蚀,造成海岸沙丘整体性的高度降低和体积减小。其次,不同类型海岸沙丘因其形态及其附近地形与植被等环境条件的差异引起了不同类型海岸沙丘形态变化的差别,如仙岐宫附近的海滩较陡但海岸较为平坦且较为宽阔（图1、图3）,因海滩地势较陡其近滨海滩接受来自海中物质的能力较弱,对近滨海滩沙物质的补充不足,故在台风强力侵蚀下海滩和海岸沙席前缘因侵蚀大于补给致使高程降低,但在向陆推进中风速逐渐降低,尤其是受沙席后缘林地阻降后风速降低,输沙能力下降致使由侵蚀变为沉积,故其形态变化表现为海岸沙席前缘高程降低、中部高程逐渐增加直至沙席后缘高程升至最大,沙丘体积也因接受来自岸线附近海滩的沙物质还有所增加;白犬山爬坡沙丘分布于白犬山的丘陵迎风坡上,受下伏地形影响沙丘自海向陆高程有较大升高,致使其整体均处于风力直接吹蚀之下（图1、图3）,虽因爬坡沙丘上微地形及植被分布与生长的差异不同造成测点的高程变化不一,但整个爬坡沙丘受台风登陆时强风力侵蚀高程降低明显;白鸽屿后的海岸前丘和芦洋的横向沙丘,受海岸地形作用附近海滩地势平缓（图1）,邻陆海滩接受来自海中物质相对较易,对近滨海滩沙物质的补充较为充足,岸线附近海滩及邻近沙丘的迎风坡坡脚甚至迎风坡因接受台风大浪携带来的泥沙造成其高程有不同程度的增加,直至达到一定高度尤其是近沙丘丘顶附近后台风的风力侵蚀作用才逐渐显现,使得其丘顶直至背风坡坡脚乃至丘间低地的高程都因台风的强烈风力侵蚀而降低,同时也在沙丘体上因原有微地形凸凹不同及植被盖度差异等造成不同测点存在高程升高或降低的不同变化。上述说明,海岸沙丘形态对台风响应的性质与程度并非仅取决于台风特征,还与海岸沙丘类型及其形态、下伏地貌与植被分布等密切相关。5 结论
（1）平潭岛海岸沙丘形态对台风“麦德姆”的响应整体是以沙丘高度降低、体积减小为基本特征。（2）平潭岛不同类型海岸沙丘对台风“麦德姆”形态响应的差异较大,其中海岸沙席高度增加和体积扩大的响应特点尤为突出,且不同海岸沙丘部位的响应也存在一定差异。
（3）海岸沙丘形态对台风的响应,应是在台风强劲的风力侵蚀作用之下台风、下伏地貌、沙丘形态和植被分布等海、陆、气三相因子交互作用的结果,并非仅取决于台风强度。
限于研究条件,上述仅为一次台风的代表性观测结果,关于台风频率、强度及风向等的作用问题尚需更多进一步的观测和研究。
The authors have declared that no competing interests exist.
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| [1] | Landward aeolian sediment transport of swash-deposited sand (Section B) is dependent on the subaerial beach topography and the aerodynamic flow regime across that topography. Characteristic profile shapes are ascribed to each beach type (dissipative, intermediate and reflective). Aeolian sand transport rates are potentially highest on dissipative beaches, moderate on intermediate beaches and lowest on reflective beaches. These rates determine the potential size of foredunes which are correspondingly largest on dissipative beaches and smallest on reflective beaches. The combination of mode and frequency of beach/dune erosion, rates of aeolian sand transport, and foredune volume and morphology provide an explanation of the nature and morphology of landward-occurring, large-scale dune systems. Dissipative beaches are frequently characterised by large-scale transgressive dune sheets; intermediate, by a trend from large-scale parabolic dune systems (high-wave energy) to small-scale blowouts (low-wave energy); and reflective beaches by minimal dune development. |
| [2] | Coastal Dunes Form and Process Edited by Karl F. Nordstrom Norbert Psuty Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey 08903, USA and Bill Carter Department of Environmental Studies, University of Ulster, Coleraine, Co. Londonderry, BT52 1SA, Northern Ireland Coastal Morphology and Research Series Series Editor: Eric C. F. Bird This book deals with the formation and establishment of coastal dunes - considering both forms and processes in a wide variety of environments. These landforms are among the most sensitive to environmental change, yet they provide extensive protection against both short-term erosion and flooding and long-term sea-level rise. Until now, there has not been any major book to deal specifically with coastal dunes. The current volume surveys a range of dune features, such as the ephemeral characteristics in the rapidly subsiding Mississippi delta, the extensive sand sheets of Australia and South Africa and the Holocene dunes of Western Europe and North America. This book will provide essential background information for ecological and management studies of coastal dunes. It will be of immense value to geomorphologists, ecologists and other environmental scientists who work on the management of coastal dunes. |
| [3] | This is a description of some aspects of the phenomenon of dune erosion as experienced on the Dutch coast with primary attention to a recently executed series of model tests. The final results of these tests have turned out to be more favourable than the results obtained from former concepts. As details on the model tests can be found in the report on model investigation of the Delft Hydraulics Laboratory (1976), they are only briefly described in this paper. |
| [4] | This paper presents the set-up and results of an extensive research programme concerning the erosion of coastal dunes during storm surges. A large number of two-dimensional and three-dimensional mobile-bed model tests has been carried out to investigate the process of dune erosion. The state of art after a series of small-scale tests is summarized. Attention is focussed on large-scale tests carried out in the Delta Flume with random waves up to 2 m significant height. Sediment concentration and orbital velocity measurements are discussed. The large-scale tests have confirmed the validity of a modelling technique based on the dimensionless fall velocity parameter H/Tw . The model results are being applied to check the safety of existing coastal dunes as a water-retaining structure that has to protect the major part of the Netherlands from inundation during storm surges. |
| [5] | |
| [6] | Dune survival is controlled by: 1) hurricane characteristics, including intensity, duration, and frequency, and 2) morphological parameters including width of the barrier island, height and width of the dunefields, vegetation type, distance of the dunes to the ocean, and continuity of the dunefields. Three processes of dune destruction are described including, from most to least severe, inundation, overwash, and scarping. The interaction of all the above factors determines the different dune responses to the storm impacts. In general, the extensive and densely woody vegetated dunefields near the bay-side shoreline survived the storms, while the discontinuous dunes with grassy vegetation near the Gulf shoreline were almost completely destroyed. |
| [7] | Greenwich Dunes, Prince Edward Island National Park, is a sandy mainland and barrier spit beach-dune complex stretching for about 10km along the northeast shore of Prince Edward Island, Canada. In October 1923, surge associated with an intense storm produced catastrophic overwash along the whole length of the study area. Subsequent evolution of the system was quantified from historic aerial photographs taken in 1936, 1953, 1971, 1997, and 2005. Orthophoto mosaics were generated for each photo set using PCI Geomatica OrthoEngine, a digital photogrammetric software. Linear changes in shoreline position and areal changes in geomorphic units were evaluated for each photo set. In addition, digital elevation models (DEMs) were extracted from the 1953, 1971, and 1997 aerial photos, enabling analysis of topographic and volumetric changes. The 1936 photos show complete destruction of all foredunes, with overwash and transgressive dunes extending 300 to 600m inland. A descriptive model of the stages of evolution of the system is proposed based on the processes controlling overwash healing and dune stabilization. Detailed topographic and volumetric changes associated with the development of an extensive transgressive dunefield and subsequent stabilization as a result of reduced sand supply due to the growth of a new vegetated foredune complex and vegetation colonization are doccumented for each stage. It was nearly 40years before a continuous foredune system was re-established and a further 30years before the inland transgressive dunes became completely stabilized.Les dunes Greenwich du Parc national de l'02le-du-Prince-07douard forment un complexe de région continentale et de barre-dunes qui s'étend sur une dizaine de kilomètres le long de la c00te nord-est de l'02le-du-Prince-07douard, Canada. En octobre 1923, une vague de grosse tempête a causé un débordement catastrophique tout le long du secteur à l'étude. L'évolution subséquente du système a été quantifiée à partir de photographies aériennes historiques prises en 1936, 1953, 1971, 1997 et 2005. Des mosa07ques orthophotographiques ont été générées pour chaque ensemble de photos au moyen du logiciel numérique de photogrammétrie OrthoEngine de PCI Geomatica. Les changements de position de la ligne de rivage et les changements de superficie des unités géomorphologiques ont été évalués pour chaque ensemble de photos. De plus, des modèles numériques et d'élévation ont été extraits des photographies aériennes prises en 1953, 1971 et 1997, permettant d'analyser les changements topographiques et volumétriques. Les photos de 1936 montrent la destruction complète de toutes les avant-dunes; elles montrent aussi du matériau de débordement et des dunes transgressives s'étendant de 300 à 600 m à l'intérieur des terres. Un modèle descriptif des étapes de l'évolution du système est proposé basé sur les processus contr00lant le rétablissement à la suite du débordement et la stabilisation des dunes. Les changements topographiques et volumétriques détaillés associés au développement d'un grand champ de dunes transgressives et la stabilisation subséquente résultant d'un apport moindre en sable en raison du développement d'un nouveau complexe d'avant-dunes végétalisé et la colonisation par la végétation sont documentés pour chaque étape. Une période de près de 40 ans a été nécessaire pour que se rétablisse un système continu d'avant-dures et 30 autres années avant que les dunes transgressives à l'intérieur des terres ne soient complètement stabilisées. |
| [8] | Abstract Cabo Falso is located on the southern coast of the Baja California peninsula. The beach is broad and wide with a steep face and tall foredunes on the backshore. Landwards, an active, predominantly parabolic dune field has developed with average heights of 30 m. Part of the field is used by recreational all-terrain vehicles. The main goal of this study was to identify the principal morphodynamic characteristics of the deposits influenced by these recreational activities and affected by Hurricane Juliette in 2001. The morphology of the study area was monitored using seasonal topographic profiles, examination of aerial photographs from 1972 and 1993, and on-site photographs (November 1999 to April 2002). The topographic profiles indicated that the erosion period for both the beach and the dunes was June to December. Hurricane Juliette was the responsible for most of the observed erosion. The greatest sediment accumulation occurred between December 2001 and February 2002, associated with the onset of... |
| [9] | Monitoring of frontal dune erosion and accretion on the Sefton coast in northwest England over the past 50years has revealed significant spatial and temporal variations. Previous work has shown that the spatial variations primarily reflect longshore differences in beach and nearshore morphology, energy regime and sediment budget, but the causes of temporal variations have not previously been studied in detail. This paper presents the results of work carried out to test the hypothesis that a major cause of temporal variation is changes in the frequency and magnitude of storms, surges and resulting high tides. Dune toe erosion/accretion records dating from 1958 have been compared with tide gauge records at Liverpool and Heysham. Relatively high dune erosion rates at Formby Point 1958鈥1968 were associated with a relatively large number of storm tides. Slower erosion at Formby, and relatively rapid accretion in areas to the north and south, occurred during the 1970's and 1980's when there were relatively few major storm tides. After 1990 rates of dune erosion at Formby increased again, and dunes to the north and south experienced slower accretion. During this period high storm tides have been more frequent, and the annual number of hours with water levels above the critical level for dune erosion has increased significantly. An increase in the rate of mean sea-level rise at both Liverpool and Heysham is evident since 1990, but we conclude that this factor is of less importance than the occurrence of extreme high tides and wave action associated with storms. The incidence of extreme high tides shows an identifiable relationship with the lunar nodal tidal cycle, but the evidence indicates that meteorological forcing has also had a significant effect. Storms and surges in the eastern Irish Sea are associated with Atlantic depressions whose direction and rate of movement have a strong influence on wind speeds, wave energy and the height of surge tides. However, preliminary analysis has indicated only a modest relationship between dune erosion/accretion rates and the North Atlantic Oscillation index. |
| [10] | . On 10th March 2008, the high energy storm Johanna hit the French Atlantic coast, generating severe dune erosion on Vougot Beach (Brittany, France). In this paper, the recovery of the dune of Vougot Beach is analysed through a survey of morphological changes and hydrodynamic conditions. Data collection focused on the period immediately following storm Johanna until July 2010, i.e. over two and a half years. Results showed that the dune retreated by a maximum of almost 602m where storm surge and wave attack were the most energetic. Dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre- and post-storm dune toe, and reducing impacts of the storm surge. Dune recovery started in the month following the storm event and is still ongoing. It is characterised by the construction of “secondary” embryo dunes, which recovered at an average rate of 4–4.502cm per month, although average monthly volume changes varied from 61021 to 202m 3 .m 61021 . These embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune. These dune-construction processes were facilitated by growth of vegetation on low-profile embryo dunes promoting backshore accretion. After more than two years of survey, the sediment budget of the beach/dune system showed that more than 10,00002m 3 has been lost by the upper tidal beach. We suggest that seaward return currents generated during the storm of 10th March 2008 are responsible for offshore sediment transport. Reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross-shore sediment redistribution inducing net erosion in the tidal zone. |
| [11] | Holocene forested coastal dunes fringe the Atlantic coast of western Portugal. Mapping of dunes in the field and using air photographs shows a range of forms reflecting dominant northwest and westerly onshore wind regimes. Planting of maritime pine forests in the thirteenth and twentieth centuries was initiated because of sand invasion causing problems for human settlement and agriculture. Early Holocene dunes have a well-developed podsol and date to 9.7 and 8.2 ka, suggesting at least some of these sands may have been emplaced during a global cooling event. Significant transgressive dune accretion at 2.2 and 1.5 ka, implies abundant sand supply and strong onshore winds. The most recent dune-building period dates to AD 177009“1905 and coincides with a predominantly negative winter North Atlantic Oscillation index (NAOi). Accretion of dunes along the Portuguese coast appears out of phase with dune development in southwest France, which may reflect different Atlantic storm tracks driven by changes in the dominance and state of the NAOi. |
| [12] | Sand dunes on the island of Anholt (Denmark) in the middle of Kattegat form a relatively barren, temperate climate aeolian system, locally termed the "Desert". The dunes have developed on top of a raised beach ridge system under the influence of dominant winds from westerly directions. They are relatively coarse-grained with an average mean grain size of 480 渭m. The last phase of aeolian activity and dune formation on Anholt started after AD 1560, when the local pine forest was removed. Historical sources report intense sand mobilization in the 17th century, and new optically stimulated luminescence (OSL) dates indicate that dune formation continued until the end of the 19th century. This period of sand drift and dune formation took place during the later part of the Little Ice Age, which is characterized by increased (summer) storminess in large parts of NW Europe. Dune stabilization in the beginning of the 20th century probably records a temporary decrease in storminess. Ground-penetrating radar mapping of the internal structures in two dunes in the western part of the Desert (a parabolic dune and a linear dune) indicates the importance of north-westerly (storm) winds during dune formation. |
| [13] | ABSTRACT This paper presents analysis of significant storm parameters’ influence on dune erosion size at particular 1-kilometer segments at the south Baltic dune coast (Dziwnow Spit). A significant storm is a one which causes dune erosion. 32 storms from the period of 1978-2009 causing significant coastal changes were chosen for the analysis. Using hierarchical cluster analysis by Ward’s method the storms were classified into 3 groups, depending on the size of the eroded dune: G1 (small), G2 (medium), and G3 (high). Dune erosion and storm parameters correlation coefficients were also calculated, as well as threshold value dividing particular groups of storms at each kilometer. This examination reveals that the greatest correlation at almost every kilometer is shown between the size of eroded dune and the sea level. Dune size is also highly correlated with the significant wave height, however correlation with the significant wave azimuth appears only in areas bordering with hydrotechnical constructions. |
| [14] | |
| [15] | Historical extreme storms that struck the Gulf Coast and Atlantic Coast regions of the United States caused several different styles of morphological response and resulted in a wide range of washover penetration distances. The poststorm erosional responses included dune scarps, channel incisions, and washouts, whereas depositional responses included perched fans, washover terraces, and sheetwash lineations. Maximum inland extent of washover penetration ranged from approximately 100 to 1000 m and estimated sediment volumes associated with these deposits ranged from about 10 to 225 m/m of beach. Unusual styles of morphological response (sheetwash lineations and incised channels) and maximum washover penetration distances are closely correlated, and they also correspond to storm intensity as defined by the Saffir-Simpson wind-speed scale. The regional morphological responses and washover penetration distances are controlled primarily by the interactions among heights and durations of storm surge relative to adjacent land elevations, differences in water levels between the ocean and adjacent lagoon, constructive and destructive interference of storm waves, and alongshore variations in nearshore bathymetry. For barrier segments that are entirely submerged during the storm, impacts can be enhanced by the combined influences of shallow water depths and organized flow within the wind field. The greatest washover penetrations and sediment accumulations are products of shallow water, confined flow, and high wind stress. Transport and deposition of washover sediments across barrier islands and into the adjacent lagoon are common processes along the Gulf of Mexico but not along the western Atlantic Ocean. This fundamental difference in storm impact underscores how microtidal and mesotidal barriers respond respectively to extreme storms, and provides insight into how different types of barrier islands will likely respond to future extreme storms and to a relative rise in sea level. |
| [16] | . Storm influence on the southern Baltic coast was examined for a 14-km long section of the Polish coast along the Dziwnow Spit based on 30years of post-storm dune erosion observations. In this study, we assumed that a significant storm causes noticeable sand dune erosion. Significant changes of the coast after each major storm were analysed based on reports from 1978 to 2008 provided by the Maritime Office, Szczecin. Thirty-two storms that caused dune losses were chosen for analysis. Correlation and hierarchical cluster analysis allowed us to distinguish three groups of storms that caused varying amounts of dune erosion: G1 (small), G2 (medium), and G3 (large). Sea level is the main parameter that influences the amount of dune erosion caused by storms on the southern Baltic coast. Factors such as maximum significant wave height, mean wave direction, storm energy and duration can also, but less significantly, influence dune erosion. The study area was divided into two sections: Dziwnow, where there are many protection measures in place, and Miedzywodzie, which has no protection measures in place. In both areas, we observed differences in the impact of sea level and significant wave height and storm groupings. Approximate minimum sea level and significant wave height thresholds were defined for particular storm groups. |
| [17] | The recovery of Santa Rosa Island in northwest Florida is characterized following Hurricane Katrina (September 2005), which was preceded by Hurricanes Ivan (2004) and Dennis (2005). Beach and dune recovery were quantified to the east and west of Pensacola Beach through a comparison of LiDAR data collected immediately following Hurricane Katrina and in July 2006 after almost a year of recovery. ... |
| [18] | A 2DH numerical, model which is capable of computing nearshore circulation and morphodynamics, including dune erosion, breaching and overwash, is used to simulate overwash caused by Hurricane Ivan (2004) on a barrier island. The model is forced using parametric wave and surge time series based on field data and large-scale numerical model results. The model predicted beach face and dune erosion reasonably well as well as the development of washover fans. Furthermore, the model demonstrated considerable quantitative skill (upwards of 66% of variance explained, maximum bias 0.21m) in hindcasting the post-storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied. The prediction skill ranged between 0.66 and 0.77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied. The sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay. The model sensitivity to the sheet flow sediment transport limiter, which served as a proxy for unknown factors controlling the resistance to erosion, was significantly greater than the sensitivity to the hydraulic forcing parameters. If no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response. |
| [19] | |
| [20] | During the summer of 2005, Hurricane Dennis overwashed the eastern portion of St. George Island, part of the northwest barrier island chain located along the Florida Panhandle. In this paper, LiDAR-based morphological changes of the barrier island are analyzed, along with the short-term post-storm recovery of secondary dunes. Results show that overwash from the storm surge removed nearly the entire foredune complex, and the initial breaching probably occurred where the complex was either low or discontinuous; in these locations, beach widening was less. In contrast, approximately 10m of beach widening occurred where foredunes were higher and continuous, implying that more sediment was available for seaward transport during storm conditions. The secondary dunes recovered at an average linear rate of 3–4cm per month in the presence of vegetation, although monthly averages varied from 611.5 to 1.4m 3 /m and total volume changes varied from 6117.9 to 16.4m 3 /m for the duration of the study. Furthermore, vegetation deterred dune migration, thus favoring dune growth and reducing erosion due to wind. In contrast, the absence of vegetation inhibited dune growth. Insignificant changes in elevation occurred in areas of storm debris or lag deposit. Finally, distributions of topographic gradients and curvature calculated numerically from pre- and post-storm LiDAR data are introduced as a potential tool in determining the relative post-storm recovery of the dune field. |
| [21] | |
| [22] | By using digital elevation model (DEM) data derived from light detection and ranging (LIDAR) data, an approximately 70-km stretch of the southern North Carolina coastline was studied. The coastline consists of five barrier islands located between Masonboro Island at the southern extent and Topsail Island at the northern extent. The high-resolution DEM data allowed for a comprehensive visual/quantitative investigation into the spatial patterns of morphologic change that occurred to the barrier islands' oceanfront beaches between 1997 and 2000. This study also demonstrated the usefulness of using laser altimetry to examine barrier islands' response to level of tropical activity, and showed that the coastal process of overwash was recognized as an integral component of barrier island landward migration. Means of net volumetric change per unit area (m 3 /m 2 ) for study areas of different beach management practices, characterized as developed, undeveloped, and nourished beaches on a yearly basis for the period between 1997 and 2000 were derived. t -Test of the means has been conducted, and results showed that beaches differed statistically if different management practices were applied to them, and the differences were minimized or disappeared if sequential hurricanes or storms affected the beaches. |
| [23] | Antecedent geology plays a crucial role in determining the inner-shelf, nearshore, and onshore geomorphology observed in coastal systems. However, the influence of the geologic framework on a system is difficult to extract when evaluating responses to changes due to storms and anthropogenic modifications, and few studies have quantified the potential for these influences in dune/beach environments. This study evaluates topographic change to the dune/beach system at Fire Island, New York over a ten year period (1998-2008) at two sites representing eastern and western reaches of the island where morphology has been shown to vary. The sites are situated along swaths of coast eroding differentially and where the inner shelf geologic framework differs substantially. Fewer large storms occurred in the first half of the study period, compared with the later part of the study period which includes several severe and prolonged extratropical storms. Additionally, a major beach replenishment project was conducted at one of the study sites. Topographic data from LiDAR and RTK GPS surveys are used to construct high-resolution 3D surfaces, which are used to determine volumetric change and to extract 2D alongshore features and profiles for analysis. The study sites help to further characterize morphologic differences between eastern and western reaches of the island. The western site displays higher sand volumes, lower dunes, and a lower gradient profile slope when compared with the eastern site. In addition to these fundamental morphologic differences, the two sites also differ significantly in their response to coastal storms and in the fact that their replenishment histories are different. The replenished areas show reduced vulnerability to storms through minimal volume loss and shoreline accretion that should be considered when evaluating the response of replenished areas to episodic events. We propose that site-specific differences evident throughout the study period can be linked to alongshore variations in the framework geology of the system. Anthropogenic modifications may have intensified differences already inherent in the system. (C) 2010 Elsevier B.V. All rights reserved. |
| [24] | Observations from the stereo method were used to quantify wave runup and dune erosion. We tested a variety of runup statistics based on a Gaussian distribution of swash properties, and found that the most predictive statistic for dune erosion was the 16% exceedance elevation above the dune base, lower than the often used 2% exceedance value. We found that the parameterization of runup was sensitive to the definition of beach slope and that the most accurate beach slope for predicting runup was through the region of the beach profile defined by the mean water level plus one standard deviation of swash. The dune base retreated along a relatively constant trajectory that was a half of the initial beach slope. Finally, a simple model for dune erosion was tested and found to reproduce 64% of the observed variance in dune erosion rate given known forcing at the dune and 49% of the observed variance in dune erosion rate given parameterized forcing. Integrating the simple model over time, 93% of the observed dune retreat distance was reproduced given offshore forcing. |
| [25] | . <FONT face=Verdana>波浪-海滩-沙丘相互作用模式是对海岸沙丘形成与演化机理的宏观解析，是了解和认识海岸沙丘形态、类型与规模等的区域差异的基本途径，与海岸沙丘表面风沙流过程研究一样是研究海岸风沙问题不可或缺的重要方面。在对20世纪80年代以来国内外关于波浪-海滩-沙丘间相互作用模式研究历程回顾的基础上，重点总结和概述了国外所提出的波浪-海滩-沙丘间相互作用模式，包括小尺度的波浪-海滩-沙丘相互作用模式、中尺度的波浪-海滩-沙丘相互作用模式等，并展望了未来我国波浪-海滩-沙丘相互作用模式研究的基本方向与主要内容。</FONT> <FONT face=Verdana>波浪-海滩-沙丘相互作用模式是对海岸沙丘形成与演化机理的宏观解析，是了解和认识海岸沙丘形态、类型与规模等的区域差异的基本途径，与海岸沙丘表面风沙流过程研究一样是研究海岸风沙问题不可或缺的重要方面。在对20世纪80年代以来国内外关于波浪-海滩-沙丘间相互作用模式研究历程回顾的基础上，重点总结和概述了国外所提出的波浪-海滩-沙丘间相互作用模式，包括小尺度的波浪-海滩-沙丘相互作用模式、中尺度的波浪-海滩-沙丘相互作用模式等，并展望了未来我国波浪-海滩-沙丘相互作用模式研究的基本方向与主要内容。</FONT> |
| [26] | . 基于华南8处海滩6次风暴追踪 调查资料,从不同地貌动力类型讨论了华南海滩风暴响应特征:耗散型海滩通常表现为滨后沙丘的侵蚀和滩面的调整,低潮阶地型海滩上部滩面响应剧烈,沙坝型海 滩在风暴期间通常表现为滩肩的侵蚀和沙坝的向海迁移或潮间带沙坝夷平消失,无护岸和滨后沙丘发育的海岸易产生冲越.文章深入探讨了风暴作用下华南海滩后滨 响应差异、滩面坡度变化规律,提出了εT作为海滩地貌动力学特征参数,研究了海滩地貌动力学特征及其风暴响应强度的关系.结果表明:海滩固有的地貌动力学 特性对其风暴响应影响明显,海滩耗散性越强,海滩风暴响应迟钝;海滩反射性增强,海滩风暴响应剧烈. 基于华南8处海滩6次风暴追踪 调查资料,从不同地貌动力类型讨论了华南海滩风暴响应特征:耗散型海滩通常表现为滨后沙丘的侵蚀和滩面的调整,低潮阶地型海滩上部滩面响应剧烈,沙坝型海 滩在风暴期间通常表现为滩肩的侵蚀和沙坝的向海迁移或潮间带沙坝夷平消失,无护岸和滨后沙丘发育的海岸易产生冲越.文章深入探讨了风暴作用下华南海滩后滨 响应差异、滩面坡度变化规律,提出了εT作为海滩地貌动力学特征参数,研究了海滩地貌动力学特征及其风暴响应强度的关系.结果表明:海滩固有的地貌动力学 特性对其风暴响应影响明显,海滩耗散性越强,海滩风暴响应迟钝;海滩反射性增强,海滩风暴响应剧烈. |
| [27] | . 通过对沙坝—泻湖岸型砂质海滩 地貌的蚀淤变化分析结果表明,在台风"艾利"袭击下,台风移动路径右侧海滩的蚀淤变化比左侧海滩的蚀淤变化明显,而且海滩的侵蚀和淤积主要集中在中潮带附 近。同一区域,位于遮蔽带内的湖里村海滩淤积加重,切线段的下掘村海滩强烈侵蚀;而同样位于遮蔽带内的大埕湾东侧海滩上淤下蚀,整体表现为侵蚀,切线段的 西侧海滩强烈淤积。 通过对沙坝—泻湖岸型砂质海滩 地貌的蚀淤变化分析结果表明,在台风"艾利"袭击下,台风移动路径右侧海滩的蚀淤变化比左侧海滩的蚀淤变化明显,而且海滩的侵蚀和淤积主要集中在中潮带附 近。同一区域,位于遮蔽带内的湖里村海滩淤积加重,切线段的下掘村海滩强烈侵蚀;而同样位于遮蔽带内的大埕湾东侧海滩上淤下蚀,整体表现为侵蚀,切线段的 西侧海滩强烈淤积。 |
| [28] | . 利用福建长乐江田下沙砂质海滩台风前后两次野外调查资料，探讨了该处沙滩地貌和沉积物组合分布的基本特征；初步研究了该处沙滩对0418号台风“艾利”的响应模式。研究结果表明，下沙沙滩剖面沉积物以细砂和中细砂为主，台风前后采集的18个样品中，细砂6个，占总样品量的33％；中细砂11个，占总样品量的6l％。沉积物结构上具有三维均匀性，沉积特征单一，剖面地形具有典型的夷直海岸特点，前滨滩面宽阔平坦，后滨沙丘带发育，岸线平直，受台风“艾利”作用，剖面后滨和高潮带遭受严重侵蚀，后滨低沙丘带平均蚀退超过6m，并出现高度为0．5～1．0m间的直立侵蚀陡坎、海滩沉积物对台风的响应相对较弱，台风过后剖面表层沉积物的平均粒径（MzФ）均值由2．48变为2．39，粒度稍有变大；分选系数（σiФ）平均值由0．52变为0．63，分选稍有变差；偏度（SkiФ）平均值由-0．02变为0．01，峰态（KgФ）平均值由0．96变为1．13；偏度和峰度没有明显变化，剖面底层沉积物对0418号台风“艾利”的响应特征与表层沉积物的沉积响应相似。 利用福建长乐江田下沙砂质海滩台风前后两次野外调查资料，探讨了该处沙滩地貌和沉积物组合分布的基本特征；初步研究了该处沙滩对0418号台风“艾利”的响应模式。研究结果表明，下沙沙滩剖面沉积物以细砂和中细砂为主，台风前后采集的18个样品中，细砂6个，占总样品量的33％；中细砂11个，占总样品量的6l％。沉积物结构上具有三维均匀性，沉积特征单一，剖面地形具有典型的夷直海岸特点，前滨滩面宽阔平坦，后滨沙丘带发育，岸线平直，受台风“艾利”作用，剖面后滨和高潮带遭受严重侵蚀，后滨低沙丘带平均蚀退超过6m，并出现高度为0．5～1．0m间的直立侵蚀陡坎、海滩沉积物对台风的响应相对较弱，台风过后剖面表层沉积物的平均粒径（MzФ）均值由2．48变为2．39，粒度稍有变大；分选系数（σiФ）平均值由0．52变为0．63，分选稍有变差；偏度（SkiФ）平均值由-0．02变为0．01，峰态（KgФ）平均值由0．96变为1．13；偏度和峰度没有明显变化，剖面底层沉积物对0418号台风“艾利”的响应特征与表层沉积物的沉积响应相似。 |
| [29] | |
| [30] | . 于1990-1994年，对黄、渤海海岸风沙地貌、风沙沉积、风沙灾害和土地沙漠化现象进行详细的外业调查、测量和填图。在此基础上，利用GIS技术原理，对海岸风沙地貌进行系统的分类研究，对海岸风沙地貌分布规律和发育模式进行较深入的探讨。结果表明，研究区风沙地貌、风沙灾害和土地沙漠化现象主要分布在冬、春季气候干旱、风力强而持久、砂源丰富的渤海海岸和山东半岛北岸的砂质海岸地区，海岸沙丘和风成砂地总面积达700多km2，海岸风沙地貌的发育模式受地貌背景、海岸带风场和砂源条件的控制。 于1990-1994年，对黄、渤海海岸风沙地貌、风沙沉积、风沙灾害和土地沙漠化现象进行详细的外业调查、测量和填图。在此基础上，利用GIS技术原理，对海岸风沙地貌进行系统的分类研究，对海岸风沙地貌分布规律和发育模式进行较深入的探讨。结果表明，研究区风沙地貌、风沙灾害和土地沙漠化现象主要分布在冬、春季气候干旱、风力强而持久、砂源丰富的渤海海岸和山东半岛北岸的砂质海岸地区，海岸沙丘和风成砂地总面积达700多km2，海岸风沙地貌的发育模式受地貌背景、海岸带风场和砂源条件的控制。 |
| [31] | . 通过对我国海岸风沙地貌类型体系及其分布规律的分析总结,提出了一个包括2类、3亚类和13个三级形态类型的中国海岸风沙地貌分类体系,简要介绍了各类海岸风沙地貌的分布,总结了我国海岸风沙地貌的分布特点及其规律。结果表明,我国海岸风沙地貌具有分布范围广泛,规模较小且分布零散,分布地形多样,河口地区分布较集中,区域特征显著,类型与规模差异较大等特点,究其原因是由各地的沙源、气候与地势等海岸风沙地貌形成发育条件的差异造成。 通过对我国海岸风沙地貌类型体系及其分布规律的分析总结,提出了一个包括2类、3亚类和13个三级形态类型的中国海岸风沙地貌分类体系,简要介绍了各类海岸风沙地貌的分布,总结了我国海岸风沙地貌的分布特点及其规律。结果表明,我国海岸风沙地貌具有分布范围广泛,规模较小且分布零散,分布地形多样,河口地区分布较集中,区域特征显著,类型与规模差异较大等特点,究其原因是由各地的沙源、气候与地势等海岸风沙地貌形成发育条件的差异造成。 |
| [32] | . <p>运用探地雷达对河北昌黎海岸带横向沙脊的沉积构造进行探测,通过对探地雷达探测影像进行处理与解译,获得海岸沙丘约20 m深度范围内的海岸横向沙脊沉积构造图像,包括沉积层理的倾向、倾角与平面展布信息等。研究发现,昌黎海岸横向沙脊北段的沉积构造主要由高角度交错层理和波状交错层理组成,两者之间界面应为古海滩沿岸沙坝的顶面。界面以上发育稳定的向SWW倾斜的高角度交错层理,倾角约为30°~32°,为向岸风作用形成的前积层理;横向沙脊的丘顶可见槽状交错层理,可能是沙丘脊顶部沉积作用对风向季节性变化的响应。界面以下波状交错层理发育,为波浪作用形成的海滩沉积构造。结合前人对探测区地层调查以及全新世晚期以来海岸线变迁研究成果综合分析,认为海岸横向沙脊是大约2000 aBP以来,以澙湖海滩沿岸沙坝为基础经长期风力吹扬作用持续增长而发育的风成沙丘。</p> <p>运用探地雷达对河北昌黎海岸带横向沙脊的沉积构造进行探测,通过对探地雷达探测影像进行处理与解译,获得海岸沙丘约20 m深度范围内的海岸横向沙脊沉积构造图像,包括沉积层理的倾向、倾角与平面展布信息等。研究发现,昌黎海岸横向沙脊北段的沉积构造主要由高角度交错层理和波状交错层理组成,两者之间界面应为古海滩沿岸沙坝的顶面。界面以上发育稳定的向SWW倾斜的高角度交错层理,倾角约为30°~32°,为向岸风作用形成的前积层理;横向沙脊的丘顶可见槽状交错层理,可能是沙丘脊顶部沉积作用对风向季节性变化的响应。界面以下波状交错层理发育,为波浪作用形成的海滩沉积构造。结合前人对探测区地层调查以及全新世晚期以来海岸线变迁研究成果综合分析,认为海岸横向沙脊是大约2000 aBP以来,以澙湖海滩沿岸沙坝为基础经长期风力吹扬作用持续增长而发育的风成沙丘。</p> |
| [33] | . 发展中长时间尺度的海岸演化预测方法与机理模型,是目前国际海岸演化研究领域关注的焦点和最具挑战性课题。本文系统性地回顾了近半个世纪以来不同时间尺度海岸演化模式的研究发展历程和成果,从动力机制和时间尺度两个方面对海岸演化机理模型存在的主要建模瓶颈问题进行了系统总结。通过对渤海湾西岸近一个半世纪以来海岸演化机制的初步分析,提出了以泥沙收支、环流输送、波浪掀沙以及波气候变化等要素作为年代际尺度海岸演化主要驱动因子,基于驱动力概化与统计升尺度有机衔接的年代际尺度海岸演化机理模型的动力—统计建模方法框架新思路,为推动海岸演化动力学理论体系和中长时间尺度海岸演化预测方法创新,提供了重要科学依据和借鉴。 发展中长时间尺度的海岸演化预测方法与机理模型,是目前国际海岸演化研究领域关注的焦点和最具挑战性课题。本文系统性地回顾了近半个世纪以来不同时间尺度海岸演化模式的研究发展历程和成果,从动力机制和时间尺度两个方面对海岸演化机理模型存在的主要建模瓶颈问题进行了系统总结。通过对渤海湾西岸近一个半世纪以来海岸演化机制的初步分析,提出了以泥沙收支、环流输送、波浪掀沙以及波气候变化等要素作为年代际尺度海岸演化主要驱动因子,基于驱动力概化与统计升尺度有机衔接的年代际尺度海岸演化机理模型的动力—统计建模方法框架新思路,为推动海岸演化动力学理论体系和中长时间尺度海岸演化预测方法创新,提供了重要科学依据和借鉴。 |
| [34] | . |
| [35] | . 本文探讨长乐东部沿海及海坛岛两地海岸风沙地貌的成因,作者根据野外调查结果分析得出风况、沙源和地形空间是长乐东部沿海及海坛岛风沙地貌发育的基本条件,认为气候变干的趋势和人类活动因素是加速海岸风沙地貌形成的触发因素。 本文探讨长乐东部沿海及海坛岛两地海岸风沙地貌的成因,作者根据野外调查结果分析得出风况、沙源和地形空间是长乐东部沿海及海坛岛风沙地貌发育的基本条件,认为气候变干的趋势和人类活动因素是加速海岸风沙地貌形成的触发因素。 |
| [36] | . 论述了海坛岛海岸风沙堆积物的沉积特征，对风沙地貌的基本类型进行了划分，分析其发育的基本条件和触发因素，研究其发育历史。 论述了海坛岛海岸风沙堆积物的沉积特征，对风沙地貌的基本类型进行了划分，分析其发育的基本条件和触发因素，研究其发育历史。 |
| [37] | . 在台湾海峡众多的海岛中,平潭岛以风大、沙多著称.风沙作用发生 在2400a B.P.左右至今,风沙作用使该岛增加了90km2的土地.本文论述的海岛东部风沙地貌系列受NNE优势风控制,是泥砂在风和水动力作用下复合搬运与沉积 的产物,以堆积型为主,伴生侵蚀-刻蚀型.风沙在七里埔、苍海造就了约14km2的土地,在岛的中部建造了淡水湖泊"岚湖",在田美沃留下了风蚀刻痕微地 貌.此外,风沙活动还影响了海岛东部地区海岸沙滩的冲淤变化.平潭岛风沙地貌系列是台湾海峡一个独特的地质景观,其对海岸带环境变化的影响在中国东部极具 代表性,在我国沿海风沙地层学和地貌学上均有较高的科研价值. 在台湾海峡众多的海岛中,平潭岛以风大、沙多著称.风沙作用发生 在2400a B.P.左右至今,风沙作用使该岛增加了90km2的土地.本文论述的海岛东部风沙地貌系列受NNE优势风控制,是泥砂在风和水动力作用下复合搬运与沉积 的产物,以堆积型为主,伴生侵蚀-刻蚀型.风沙在七里埔、苍海造就了约14km2的土地,在岛的中部建造了淡水湖泊"岚湖",在田美沃留下了风蚀刻痕微地 貌.此外,风沙活动还影响了海岛东部地区海岸沙滩的冲淤变化.平潭岛风沙地貌系列是台湾海峡一个独特的地质景观,其对海岸带环境变化的影响在中国东部极具 代表性,在我国沿海风沙地层学和地貌学上均有较高的科研价值. |
| [38] | . 根据海岸风沙运动的特点和单站差分RTKGPS的特点,提出了应用多站计算7个参数Δx、Δy、Δz、Ωx、Ωy、Ωz和K的坐标平滑处理技术和求解高程异常值ζ进行曲面拟合的多站差分RTKGPS技术,并对海岸风沙观测点的高程进行实际测量,选取186个观测点的结果与传统的水准测量观测出来的结果进行比较,其高程误差范围在0.6～1.0 mm之间。表明多站差分RTKGPS技术的测量精度能满足海岸风沙观测的精度要求。 根据海岸风沙运动的特点和单站差分RTKGPS的特点,提出了应用多站计算7个参数Δx、Δy、Δz、Ωx、Ωy、Ωz和K的坐标平滑处理技术和求解高程异常值ζ进行曲面拟合的多站差分RTKGPS技术,并对海岸风沙观测点的高程进行实际测量,选取186个观测点的结果与传统的水准测量观测出来的结果进行比较,其高程误差范围在0.6～1.0 mm之间。表明多站差分RTKGPS技术的测量精度能满足海岸风沙观测的精度要求。 |
| [39] | . 采用RTKGPS测量技术与方法,2006～2008年连续三年共9次对我国海岸沙丘主要分布区域之一的河北昌黎黄金海岸翡翠岛的一个典型海岸横向沙脊进行了三个横剖面的高精度观测。海岸横向沙脊高程、断面及其典型位置的观测结果表明,观测期间海岸横向沙脊脊顶和背风坡坡脚夏秋季东移、冬春季节西移,脊顶总体向西移动,年均最大移距1.83m,但同期观测剖面背风坡坡脚的移动距离最大仅0.16m;脊顶高程夏秋季降低、冬春季升高,观测期间脊顶高程平均降低了1.58m,而三个观测剖面的断面面积期间则分别增加了0.47%、0.79%和0.69%,故海岸横向沙脊移动与形态变化的季节性十分明显,总体上具有沙丘下部基本稳定、顶部以往复前进方式向陆缓慢移动以及沙体加积增大但脊顶高程逐渐降低的特征,其原因主要与区域风况特点及人类活动密切相关。 采用RTKGPS测量技术与方法,2006～2008年连续三年共9次对我国海岸沙丘主要分布区域之一的河北昌黎黄金海岸翡翠岛的一个典型海岸横向沙脊进行了三个横剖面的高精度观测。海岸横向沙脊高程、断面及其典型位置的观测结果表明,观测期间海岸横向沙脊脊顶和背风坡坡脚夏秋季东移、冬春季节西移,脊顶总体向西移动,年均最大移距1.83m,但同期观测剖面背风坡坡脚的移动距离最大仅0.16m;脊顶高程夏秋季降低、冬春季升高,观测期间脊顶高程平均降低了1.58m,而三个观测剖面的断面面积期间则分别增加了0.47%、0.79%和0.69%,故海岸横向沙脊移动与形态变化的季节性十分明显,总体上具有沙丘下部基本稳定、顶部以往复前进方式向陆缓慢移动以及沙体加积增大但脊顶高程逐渐降低的特征,其原因主要与区域风况特点及人类活动密切相关。 |
| [40] | . <p>依据2006~2008 年连续3 a 共9 次采用RTK GPS技术与测量方法对一个典型海岸新月形沙丘形态的高精度测量数据，分析了海岸新月形沙丘的移动方向、方式、速度以及形态变化特点。结果表明，海岸新月形沙丘具有缓慢、向陆往复式前进的移动特点，形态变化则具有随季节增减变化中高度、宽度、长度、断面面积与体积增加的加积特征，究其原因是区域风况、海岸地表覆被、沙丘形态及人类活动等共同作用的结果。</p> <p>依据2006~2008 年连续3 a 共9 次采用RTK GPS技术与测量方法对一个典型海岸新月形沙丘形态的高精度测量数据，分析了海岸新月形沙丘的移动方向、方式、速度以及形态变化特点。结果表明，海岸新月形沙丘具有缓慢、向陆往复式前进的移动特点，形态变化则具有随季节增减变化中高度、宽度、长度、断面面积与体积增加的加积特征，究其原因是区域风况、海岸地表覆被、沙丘形态及人类活动等共同作用的结果。</p> |
