Quantification of nearshore morphology based on video imaging

被引:68
作者
Alexander, PS [1 ]
Holman, RA [1 ]
机构
[1] Oregon State Univ, Corvallis, OR 97331 USA
关键词
nearshore; nearshore environment; remote sensing; morphology; sand bars; beaches;
D O I
10.1016/j.margeo.2004.04.017
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
The Argus network is a series of video cameras with aerial views of beaches around the world. Intensity contrasts in time exposure images reveal areas of preferential breaking, which are closely tied to underlying bed morphology. This relationship was further investigated, including the effect of tidal elevation and wave height on the presence of wave breaking and its cross-shore position over sand bars. Computerized methods of objectively extracting shoreline and sand bar locations were developed, allowing the vast quantity of data generated by Argus to be more effectively examined. Once features were identified in the images, daily alongshore mean values were taken to create time series of shoreline and sand bar location, which were analyzed for annual cycles and cross-correlated with wave data to investigate environmental forcing and response. These data extraction techniques were applied to images from four of the Argus camera sites. A relationship between wave height and shoreline location was found in which increased wave heights resulted in more landward shoreline positions; given the short lag times over which this correlation was significant, and that the strong annual signal in wave height was not replicated in the shoreline time series, it is likely that this relationship is a result of set-up during periods of large waves. Wave height was also found to have an effect on sand bar location, whereby an increase in wave height resulted in offshore bar migration. This correlation was significant over much longer time lags than the relationship between wave height and shoreline location, and a strong annual signal was found in the location of almost all observed bars, indicating that the sand bars are migrating with changes in wave height. In the case of the site with multiple sand bars, the offshore bars responded more significantly to changes in wave height, whereas the innermost bar seemed to be shielded from incident wave energy by breaking over the other bars. A relationship was also found between a site's mean wave height and inner sand bar location; sites with the highest wave heights tended to have sand bars farther from shore than those with relatively low wave heights. (C) 2004 Elsevier B.V. All rights reserved.
引用
收藏
页码:101 / 111
页数:11
相关论文
共 19 条
[1]  
Aarninkhof S. G. J., 1999, BACKSCATTER, V10, P8
[2]  
ALEXANDER PS, 2001, THESIS OREGON STATE
[3]  
ALLAN J, 2000, EOS T, V81, P564
[4]  
[Anonymous], CRC HDB COASTAL PROC
[5]  
BIRKEMEIER WA, 1985, USER GUIDE COASTAL E
[6]  
EMERGY SJ, 1997, DATA ANAL METHODS PH
[7]   LOCAL AND SHOALED COMPARISONS OF SEA-SURFACE ELEVATIONS, PRESSURES, AND VELOCITIES [J].
GUZA, RT ;
THORNTON, EB .
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1980, 85 (NC3) :1524-1530
[8]  
HAXEL J, 2002, THESIS OREGON STATE
[9]   Practical use of video imagery in nearshore oceanographic field studies [J].
Holland, KT ;
Holman, RA ;
Lippmann, TC ;
Stanley, J ;
Plant, N .
IEEE JOURNAL OF OCEANIC ENGINEERING, 1997, 22 (01) :81-92
[10]  
HOLMAN R, 1987, COASTAL SEDIMENTS, P929