Journal of Geographical Sciences >
Beach morphodynamic characteristics and classifications on the straight coastal sectors in the west Guangdong
Ding Yuanting, PhD, specialized in coastal environment. E-mail: dytmtt@163.com |
Received date: 2019-03-21
Accepted date: 2019-09-09
Online published: 2020-09-25
Supported by
National Science Foundation of China(41301005)
National Science Foundation of China(41701011)
Postdoctoral Science Foundation of China(2014M552118)
China Scholarship Council(201608410419)
Copyright
Currently beach morphodynamic classification is the most important foundation to conduct associated coastal geomorphological studies. This paper carried out beach morphodynamic classifications for 12 straight beaches on headland-bay coasts based on field survey and evaluated the applicability of the most widely used dimensional fall velocity parameter (Ω) and relative tidal range parameter (RTR). One reflective, five intermediate and six non-barred dissipative beaches were visually classified and sand size seemed to be a key factor to differentiate these beaches. The studied beaches were in relatively low wave energy environments (Hs < 1 m) and the absolute deep-water wave energy level of P0 = 3 KWm-1 was supposed to a critical threshold to characterize the applicability of the Ω and RTR parameters. These two morphodynamic parameters were applicable for the beaches with P0 > 3 KWm -1 and MSR < 2 m. It was found that the model of the traditional winter-and-summer profiles was not applicable in the study area in despite of distinct wave seasonality. The studied beaches were more possible to hover around a limited range due to relatively low background wave environments and variability without considering typhoon impacts, which needs further research on actual breaker wave conditions and beach morphodynamic type responses to typhoon events.
DING Yuanting , YU Jitao , CHENG Huangxin . Beach morphodynamic characteristics and classifications on the straight coastal sectors in the west Guangdong[J]. Journal of Geographical Sciences, 2020 , 30(7) : 1179 -1194 . DOI: 10.1007/s11442-020-1776-x
Figure 1 The study area showing 12 studied headland-bay beaches and wave and tide data sources in the west Guangdong. The beaches include #1-Jizhao Bay (21.392°-21.392°N, 110.847°-110.853°E), #2-Wangcun Bay (21.388°-21.418°N, 110.891°-110.929°E), #3-Aonei Bay (21.418°-21.429°N, 110.958°-110.982°E), #4- Shuidong Bay (21.429°-21.459°N, 110.997°-111.053°E), #5-Shuidong Dong (21.460°-21.469°N, 111.102°- 111.128°E), #6-Bohe Bay (21.464°-21.481°N, 111.136°-111.199°E), #7-Fuhu Bay (21.507°-21.525°N, 111.489°-111.527°E), #8-Hebei Bay (21.512°-21.534°N, 111.554°-111.598°E), #9-Hailing Bay (21.593°- 21.618°N, 111.690°-111.751°E), #10-Shili Beach (21.579°-21.604°N, 111.877°-111.911°E), #11-Dongdao Beach (21.618°-21.624°N, 111.982°-111.996°E) and #12-Sanya Bay (21.787°-21.807°N, 112.087°-112.12856°E). |
Figure 2 The variations of (a) annual mean significant wave height (Mean Hs), maximum wave height (Max. Hs) and minimum wave height (Min. Hs), and (b) annual mean significant wave period (Mean Tz), maximum wave period (Max. Tz), and minimum wave period (Min. Tz) during 1979-2017 at W3 |
Figure 3 The wave rose showing the characteristics of the monthly wave directions at W3 |
Figure 4 The variation of (a) monthly mean significant wave heights and (b) wave periods at W3 during 1979- 2017 |
Figure 5 Mean sand size and standard deviation of (a) upper intertidal profile and (b) lower intertidal profile for 12 west Guangdong beaches |
Table 1 Actual beach morphodynamic type diagnoses based on sediment characteristics, intertidal gradient, breaker type, characteristic morphology and dominant process |
Reflective | Intermediate | Non-barred dissipative | |
---|---|---|---|
Beach sites | Dongdao Beach | Bohe Bay, Fuhu Bay, Hebei Bay, Shili Beach, Sanya Bay | Jizhao Bay, Wangcun Bay, Aonei Bay, Shuidong Bay, Shuidong Dong, Hailing Bay |
Sand characteristics | Coarse sand | Mainly medium sand | Fine sand |
Intertidal gradient | Steep (>10°) | Steeper on the upper beach (6°-10°) and moderately steep on the lower beach (3°-6°) | Moderately steep on the upper beach (3°-5°) and flat on the lower beach (1°-2°) |
Breaker types | Plunging breakers | Plunging breakers | Plunging breakers during high tide, spilling breakers during low tide |
Characteristic morphology | Swash cusps and berm | Rip/bar morphology | Concave profile, featureless morphology |
Dominant process | Swash zone/surf zone | Surf zone | Surf zone/shoaling |
Figure 6 Examples of reflective, intermediate, and dissipative beach types with cross-shore profiles (left) and aerial photographic images (right) |
Figure 7 Prediction of beach morphodynamic types (R: reflective; B: barred; BD: barred dissipative; LTT+R: low tide terrace with rip; LTBR: low tide bar or rip; NBD: non-barred dissipative) within the beach morphodynamic framework based on the dimensionless fall velocity parameter (Ω) and relatively tidal range parameter (RTR). The marker sizes represent the relative gradients of the upper intertidal profiles and the right color bar reflects the absolute wave energy level for 12 studied beaches (1: Jizhao Bay; 2: Wangcun Bay; 3: Aonei Bay; 4: Shuidong Bay; 5: Shuidong Dong; 6: Bohe Bay; 7: Fuhu Bay; 8: Hebei Bay; 9: Hailing Bay; 10: Shili Beach; 11: Dongdao Beach; 12: Sanya Bay). |
The authors thank Professor Gerd Masselink in the University of Plymouth of UK for providing ECMWF's ERA-Interim reanalysis wave data, and comprehensive guidance and inspiration on beach morphodynamics, and also thank Jiang Guoyi, Gao Yan, Yuan Cheng, Jiang Bin and Liu Canhui in School of Surveying and Land Information Engineering, Henan Polytechnic University for their help on the field investigation.
[1] |
|
[2] |
|
[3] |
|
[4] |
|
[5] |
|
[6] |
|
[7] |
|
[8] |
|
[9] |
|
[10] |
|
[11] |
Compilation Committee of ''Records of Bays in China'' (CCRBC), 1999. Bays in West Guangdong. Records of Bays in China, vol. 10. Beijing: China Ocean Press, 97-101. (in Chinese)
|
[12] |
|
[13] |
|
[14] |
|
[15] |
|
[16] |
|
[17] |
|
[18] |
|
[19] |
|
[20] |
|
[21] |
|
[22] |
|
[23] |
|
[24] |
|
[25] |
|
[26] |
|
[27] |
|
[28] |
|
[29] |
|
[30] |
|
[31] |
|
[32] |
|
[33] |
|
[34] |
|
[35] |
|
[36] |
|
[37] |
|
[38] |
|
[39] |
|
[40] |
|
[41] |
|
[42] |
|
[43] |
|
[44] |
|
[45] |
|
[46] |
|
[47] |
|
[48] |
|
[49] |
|
[50] |
|
[51] |
|
[52] |
|
[53] |
|
[54] |
|
[55] |
|
[56] |
|
/
〈 | 〉 |