波浪作用下岬湾海滩蚀积特点:以澳大利亚Narrabeen海滩为例
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摘要
岬湾海岸因其特殊的岬角弧形地形,导致海岸线的冲淤与顺直海岸有明显区别.本文分析了1997～1998年澳大利亚东南部Narrabeen岬湾海滩实测数据.以1次典型的大浪过程为例,详细分析了大浪对海滩的侵蚀及其后的常浪修复期海滩岸线的演变情况,以及岬湾海滩蚀淤沿岸差异与波浪要素之间的关系.为讨论海滩岸线旋转的非偶然性及其原因,还分析了1990～2000年6次大浪事件前后的海滩旋转情况,这6次大浪事件后均有8个月以上的常浪期.研究结果表明:大浪期间海滩普遍侵蚀,常浪期间沿岸蚀积的差异性导致海滩旋转;在常浪恢复期间北部至中部剖面南方涛动指数(southern oscillation index,SOI)负相关,南部剖面与SOI指数正相关,导致北蚀南淤,从而岸线会发生旋转;伴随着SOI指数的增减,南北冲淤特性随之发生改变,海滩岸线旋转呈现周期性.
The special cape-shaped topography of a headland sandy bay is the reason its shoreline varies differently than that of a straight-line coast. The Narrabeen embayment is located on the southeastern coastline of Australia approximately 20 km north of Sydney. The enclosed sandy beach is 3.6 km in length and is composed of fine to medium quartz sand overlying sandstone bedrock, with a median sand grain size D50 of 0.3 mm. Due to the prevalence of moderate to high wave energy conditions and the exposure of the central and northern portions of the beach to the prevailing south-southeastern swell waves. The morphodynamic responses of the Narrabeen beach are highly variable and rapid alongshore. The beach state was predominantly influenced by episodic storm events throughout the year when erosion and accretion can occur. This study analyzed measurements of cross-shore profiles of the Narrabeen headland sandy bay from 1997-1998. With reference to an atypical huge-wave event, this paper describes in detail the beach erosion caused by huge-waves and the beach restoration caused by small waves after the huge-wave event. It also details the relationship between shoreline variation and wave parameters(wave height and wave angle). To discuss the regulations and causes of beach rotation, the study selected six huge wave events that occurred in 1990–2000, all of which were followed by over eight months of small waves, and analyzed the alongshore variation. The results show that the morphodynamic responses of the Narrabeen beach are highly variable and rapid alongshore. During the huge wave events, the beach was eroded and the shoreline retreated. In the aftermath, the small waves restored the beach. The difference in the shoreline variation due to small waves exhibits a rotational pattern. Wave height is related to sand volume above mean sea level and sand accumulation was rapid and high after the big nearshore wave events. The Southern Oscillation Index(SOI) is closely related to the variability in the shoreline. Time-lagged cross-correlations between monthly beach shoreline positions and the SOI were calculated to investigate the presence of stronger cross-correlations between the beach shoreline and the SOI; the central profile(profile 4) is the most sensitive to the feedback of SOI change. The small waves after a huge-wave event make beach rotation periodic. Analysis of directional wave data and the SOI suggests that beach change is driven by changes in wave height(power) and a subtle change in wave direction, both of which are positively related to the SOl. The change in the SOI induces changes in the wave angles, which leads to sediment transport. This is the most important factor in beach rotation. These results reconfirm huge-wave and small waves subaerial morphology, in particular, these results confirm that the wave height and angle, which are induced by the SOI after a huge-wave event, are key drivers of alongshore variation in headland sandy bay coastlines. Under small wave conditions, the northern and mid beach profiles have negative correlations with SOI index, while the southern beach profiles have positive correlations with SOI index. This lead to sediment erosion in the north while sediment deposition in the south. And the shoreline thereby shows a rotational pattern. With the variation of the SOI index, the sediment movement changes in each beach profile, and the shoreline's rotational pattern shows periodicity.
The special cape-shaped topography of a headland sandy bay is the reason its shoreline varies differently than that of a straight-line coast. The Narrabeen embayment is located on the southeastern coastline of Australia approximately 20 km north of Sydney. The enclosed sandy beach is 3.6 km in length and is composed of fine to medium quartz sand overlying sandstone bedrock, with a median sand grain size D50 of 0.3 mm. Due to the prevalence of moderate to high wave energy conditions and the exposure of the central and northern portions of the beach to the prevailing south-southeastern swell waves. The morphodynamic responses of the Narrabeen beach are highly variable and rapid alongshore. The beach state was predominantly influenced by episodic storm events throughout the year when erosion and accretion can occur. This study analyzed measurements of cross-shore profiles of the Narrabeen headland sandy bay from 1997-1998. With reference to an atypical huge-wave event, this paper describes in detail the beach erosion caused by huge-waves and the beach restoration caused by small waves after the huge-wave event. It also details the relationship between shoreline variation and wave parameters(wave height and wave angle). To discuss the regulations and causes of beach rotation, the study selected six huge wave events that occurred in 1990–2000, all of which were followed by over eight months of small waves, and analyzed the alongshore variation. The results show that the morphodynamic responses of the Narrabeen beach are highly variable and rapid alongshore. During the huge wave events, the beach was eroded and the shoreline retreated. In the aftermath, the small waves restored the beach. The difference in the shoreline variation due to small waves exhibits a rotational pattern. Wave height is related to sand volume above mean sea level and sand accumulation was rapid and high after the big nearshore wave events. The Southern Oscillation Index(SOI) is closely related to the variability in the shoreline. Time-lagged cross-correlations between monthly beach shoreline positions and the SOI were calculated to investigate the presence of stronger cross-correlations between the beach shoreline and the SOI; the central profile(profile 4) is the most sensitive to the feedback of SOI change. The small waves after a huge-wave event make beach rotation periodic. Analysis of directional wave data and the SOI suggests that beach change is driven by changes in wave height(power) and a subtle change in wave direction, both of which are positively related to the SOl. The change in the SOI induces changes in the wave angles, which leads to sediment transport. This is the most important factor in beach rotation. These results reconfirm huge-wave and small waves subaerial morphology, in particular, these results confirm that the wave height and angle, which are induced by the SOI after a huge-wave event, are key drivers of alongshore variation in headland sandy bay coastlines. Under small wave conditions, the northern and mid beach profiles have negative correlations with SOI index, while the southern beach profiles have positive correlations with SOI index. This lead to sediment erosion in the north while sediment deposition in the south. And the shoreline thereby shows a rotational pattern. With the variation of the SOI index, the sediment movement changes in each beach profile, and the shoreline's rotational pattern shows periodicity.
引文
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2 Feng X,Yi F,Cao H J,et al.Study on wave characteristics of nearshore area in the Radial Sand Ridges in the South Yellow Sea(in Chinese).China Ocean Eng,2018,36:62-73[冯曦,易风,曹海锦,等.南黄海辐射沙洲近岸海域波浪特性研究.海洋工程,2018,36:62-73]
3 Yuan J J,Feng X,Feng W B.Effects of radial sand ridges on tidal process in the South Yellow Sea(in Chinese).Chin Sci Bull,2018,63:2904-2918[袁金金,冯曦,冯卫兵.辐射沙洲地形对南黄海潮汐过程的影响.科学通报,2018,63:2904-2918]
4 Feng X,Olabarrieta M,Valle-Levinson A.Storm-induced semidiurnal perturbations to surges on the US Eastern Seaboard.Cont Shelf Res,2016,114:54-71
5 Zheng J,Zhang C,Demirbilek Z,et al.Numerical study of sandbar migration under wave-undertow interaction.J Water Port Coast,2013,140:146-159
6 Zhang C,Zhang Q,Zheng J H,et al.Parameterization of nearshore wave front slope.Coast Eng,2017,127:80-87
7 Feng Z,Wang Y H.Characteristics and controlling factors of middle and long term variation of beach beach section of Cape BayTaking Qingdao Shi Lao beach as an example(in Chinese).Mar Sci,2016,7:100-109[冯哲,王永红.岬湾海滩剖面中长期变化特征及其控制因素--以青岛石老人海滩为例.海洋科学,2016,7:100-109]
8 Splinter K D,Kearney E T,Turner I L.Drivers of alongshore variable dune erosion during a storm event:Observations and modelling.Coast Eng,2018,131:31-41
9 Short A D,Trembanis A C,Turner I L.Beach oscillation,rotation and the southern oscillation,Narrabeen beach,Australia.In:Edge B L,ed.Article Collection of American Society of Civil Engineers 27th International Conference on Coastal Engineering,Sydney.2001.2439-2452
10 Ranasinghe R,McLoughlin R,Short A,et al.The Southern Oscillation Index,wave climate,and beach rotation.Mar Geol,2004,204:273-287
11 Lee G,Nicholls R J,Birkemeier W A.Storm-driven variability of the beach-nearshore profile at Duck,North Carolina,USA,1981-1991.Mar Geol,1998,148:163-177
12 Fritz H M,Blount C,Sokoloski R,et al.Hurricane Katrina storm surge distribution and field observations on the Mississippi Barrier Islands.Estua Coast Shelf Sci,2007,74:12-20
13 Fiore M M E,D’Onofrio E E,Pousa J L,et al.Storm surges and coastal impacts at Mar del Plata,Argentina.Cont Shelf Res,2009,29:1643-1649
14 Horn D P.Mesoscale beach processes.Prog Phys Geog,2002,26:271-289
15 Schwarzer K,Diesing M,Larson M,et al.Coastline evolution at different time scales-examples from the Pomeranian Bight,southern Baltic Sea.Mar Geol,2003,194:79-101
16 Li Y,Lark M,Reeve D.Multi-scale variability of beach profiles at Duck:A wavelet analysis.Coast Eng,2005,52:1133-1153
17 Mu?oz-Perez J J,Medina R.Comparison of long-,medium and short-term variations of beach profiles withand without submerged geological control.Coast Eng,2010,57:241-251
18 Short A D.Beaches of the New South Wales Coast:A Guide to Their Nature,Characteristics,Surf and Safety.Sydney:Sydney University Press,2007
19 Short A D,Trenaman N L.Wave climate of the Sydney region,an energetic and highly variable ocean wave regime.Mar Freshwater Res,1992,43:765-791
20 Turner I L,Harley M D,Short A D,et al.A multi-decade dataset of monthly beach profile surveys and inshore wave forcing at Narrabeen,Australia.Sci Data,2016,3:160024
21 Harley M D,Turner I L,Short A D.New insights into embayed beach rotation:The importance of wave exposure and cross-shore processes.J Geophys Res:Earth Surf,2015,120:1470-1484
22 Emery K O.A simple method of measuring beach profiles.Limnol Oceanogr,1961,6:90-93
23 Harley M D,Turner I L.A simple data transformation technique for pre-processing survey data at embayed beaches.Coast Eng,2008,55:63-68
24 Booij N,Ris R C,Holthuijsen L H.A third-generation wave model for coastal regions:1 Model description and validation.J geophys res:Oceans,1999,104:7649-7666
25 Karunarathna H,Pender D,Ranasinghe R,et al.The effects of storm clustering on beach profile variability.Mar Geol,2014,348:103-112
26 Davidson M A,Turner I L,Splinter K D,et al.Annual prediction of shoreline erosion and subsequent recovery.Coast Eng,2017,130:14-25
27 Lord D,Kulmar M.The 1974 Storms Revisited:25 Years Experience in Ocean Wave Measurement along the South-East Australian Coast.Edge B L,ed.Article Collection of American Society of Civil Engineers 27th International Conference on Coastal Engineering,Sydney.2001:559-572
28 Xie M E,Liu Y.Strong ENSO event 1997(in Chinese).J Trop Meteor,1998[解明恩,刘瑜.1997年的强ENSO事件.热带气象学报,1998,14:186-192]
29 Chen Z S.Response characteristics of curved coastal beach landforms to Typhoon waves.Chin Sci Bull,1995,40:2168-2170[陈子燊.弧形海岸海滩地貌对台风大浪的响应特征.科学通报,1995,40:2168-2170]
30 Yang Z F,Wang W D.The study of extratropical cyclones in the southern hemisphere winter half year near Australia(in Chinese).JAppl Meteor,1995,6:43-49[杨祖芳,王文东.南半球冬半年澳洲附近洋面上温带气旋的研究.应用气象学报,1995,6:43-49]
31 Zhu S,Ma W M.Analysis of the southwest Pacific Ocean forecasting extratropical cyclone statistics(in Chinese).Mar Forecasts,2001,18:45-52[朱帅,马卫民.西南太平洋温带气旋统计分析.海洋预报,2001,18:45-52]
2 Feng X,Yi F,Cao H J,et al.Study on wave characteristics of nearshore area in the Radial Sand Ridges in the South Yellow Sea(in Chinese).China Ocean Eng,2018,36:62-73[冯曦,易风,曹海锦,等.南黄海辐射沙洲近岸海域波浪特性研究.海洋工程,2018,36:62-73]
3 Yuan J J,Feng X,Feng W B.Effects of radial sand ridges on tidal process in the South Yellow Sea(in Chinese).Chin Sci Bull,2018,63:2904-2918[袁金金,冯曦,冯卫兵.辐射沙洲地形对南黄海潮汐过程的影响.科学通报,2018,63:2904-2918]
4 Feng X,Olabarrieta M,Valle-Levinson A.Storm-induced semidiurnal perturbations to surges on the US Eastern Seaboard.Cont Shelf Res,2016,114:54-71
5 Zheng J,Zhang C,Demirbilek Z,et al.Numerical study of sandbar migration under wave-undertow interaction.J Water Port Coast,2013,140:146-159
6 Zhang C,Zhang Q,Zheng J H,et al.Parameterization of nearshore wave front slope.Coast Eng,2017,127:80-87
7 Feng Z,Wang Y H.Characteristics and controlling factors of middle and long term variation of beach beach section of Cape BayTaking Qingdao Shi Lao beach as an example(in Chinese).Mar Sci,2016,7:100-109[冯哲,王永红.岬湾海滩剖面中长期变化特征及其控制因素--以青岛石老人海滩为例.海洋科学,2016,7:100-109]
8 Splinter K D,Kearney E T,Turner I L.Drivers of alongshore variable dune erosion during a storm event:Observations and modelling.Coast Eng,2018,131:31-41
9 Short A D,Trembanis A C,Turner I L.Beach oscillation,rotation and the southern oscillation,Narrabeen beach,Australia.In:Edge B L,ed.Article Collection of American Society of Civil Engineers 27th International Conference on Coastal Engineering,Sydney.2001.2439-2452
10 Ranasinghe R,McLoughlin R,Short A,et al.The Southern Oscillation Index,wave climate,and beach rotation.Mar Geol,2004,204:273-287
11 Lee G,Nicholls R J,Birkemeier W A.Storm-driven variability of the beach-nearshore profile at Duck,North Carolina,USA,1981-1991.Mar Geol,1998,148:163-177
12 Fritz H M,Blount C,Sokoloski R,et al.Hurricane Katrina storm surge distribution and field observations on the Mississippi Barrier Islands.Estua Coast Shelf Sci,2007,74:12-20
13 Fiore M M E,D’Onofrio E E,Pousa J L,et al.Storm surges and coastal impacts at Mar del Plata,Argentina.Cont Shelf Res,2009,29:1643-1649
14 Horn D P.Mesoscale beach processes.Prog Phys Geog,2002,26:271-289
15 Schwarzer K,Diesing M,Larson M,et al.Coastline evolution at different time scales-examples from the Pomeranian Bight,southern Baltic Sea.Mar Geol,2003,194:79-101
16 Li Y,Lark M,Reeve D.Multi-scale variability of beach profiles at Duck:A wavelet analysis.Coast Eng,2005,52:1133-1153
17 Mu?oz-Perez J J,Medina R.Comparison of long-,medium and short-term variations of beach profiles withand without submerged geological control.Coast Eng,2010,57:241-251
18 Short A D.Beaches of the New South Wales Coast:A Guide to Their Nature,Characteristics,Surf and Safety.Sydney:Sydney University Press,2007
19 Short A D,Trenaman N L.Wave climate of the Sydney region,an energetic and highly variable ocean wave regime.Mar Freshwater Res,1992,43:765-791
20 Turner I L,Harley M D,Short A D,et al.A multi-decade dataset of monthly beach profile surveys and inshore wave forcing at Narrabeen,Australia.Sci Data,2016,3:160024
21 Harley M D,Turner I L,Short A D.New insights into embayed beach rotation:The importance of wave exposure and cross-shore processes.J Geophys Res:Earth Surf,2015,120:1470-1484
22 Emery K O.A simple method of measuring beach profiles.Limnol Oceanogr,1961,6:90-93
23 Harley M D,Turner I L.A simple data transformation technique for pre-processing survey data at embayed beaches.Coast Eng,2008,55:63-68
24 Booij N,Ris R C,Holthuijsen L H.A third-generation wave model for coastal regions:1 Model description and validation.J geophys res:Oceans,1999,104:7649-7666
25 Karunarathna H,Pender D,Ranasinghe R,et al.The effects of storm clustering on beach profile variability.Mar Geol,2014,348:103-112
26 Davidson M A,Turner I L,Splinter K D,et al.Annual prediction of shoreline erosion and subsequent recovery.Coast Eng,2017,130:14-25
27 Lord D,Kulmar M.The 1974 Storms Revisited:25 Years Experience in Ocean Wave Measurement along the South-East Australian Coast.Edge B L,ed.Article Collection of American Society of Civil Engineers 27th International Conference on Coastal Engineering,Sydney.2001:559-572
28 Xie M E,Liu Y.Strong ENSO event 1997(in Chinese).J Trop Meteor,1998[解明恩,刘瑜.1997年的强ENSO事件.热带气象学报,1998,14:186-192]
29 Chen Z S.Response characteristics of curved coastal beach landforms to Typhoon waves.Chin Sci Bull,1995,40:2168-2170[陈子燊.弧形海岸海滩地貌对台风大浪的响应特征.科学通报,1995,40:2168-2170]
30 Yang Z F,Wang W D.The study of extratropical cyclones in the southern hemisphere winter half year near Australia(in Chinese).JAppl Meteor,1995,6:43-49[杨祖芳,王文东.南半球冬半年澳洲附近洋面上温带气旋的研究.应用气象学报,1995,6:43-49]
31 Zhu S,Ma W M.Analysis of the southwest Pacific Ocean forecasting extratropical cyclone statistics(in Chinese).Mar Forecasts,2001,18:45-52[朱帅,马卫民.西南太平洋温带气旋统计分析.海洋预报,2001,18:45-52]