• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Shore and beach >Groin impacts on beaches in southern California
【24h】

Groin impacts on beaches in southern California

机译：腹股沟对南加州海滩的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The majority of the 39 high, straight, mostly shore-normal and apparently impermeable groins in southern California retain larger upcoast beaches than previously existed. Seventy percent are in groin fields and six caused problems on downcoast beaches. Analyses based on the dimensions of these groins and adjoining beaches as obtained from aerial photos, and data from leveling surveys and wave gauges, yield guides to optimize the size of the upcoast (fillet) beach as a function of effective groin length, spacing between structures, groin tip alignment, sediment size, and net and gross longshore sediment transport rates. These data also help identify locations susceptible to unwanted downcoast impacts, and point out options to mitigate those impacts. Groins retain the largest upcoast beaches per unit length of structure where the net to gross longshore transport (LST) ratio is large, sediments are sand-size (versus gravel and cobbles), and the amount of sediment transported around the structure during LST reversals is small. In addition to spacing, the alignment of the groin tips relative to one another and to the pre-project shoreline affects the size, orientation, and landward-rnmost shoreline position of beaches in groin compartments. The average ratio (for six groin fields) of 5 (spacing) to 1 (effective groin length) is larger than most rule-of-thumb recommendations. Beaches became narrower, their rate of retreat into property behind them increased, and fishhook-shaped bays began forming downcoast of effective groins where: (1) the net LST exceeded about 50,000 cubic meters per year, (2) the downcoast beach was underlain and backed by erodible material, and (3) there was a substantial alongshore component of wave energy flux along a line between the tip of the structure and the shoreline abutting the nearest downcoast anchor structure. The evolution of a hook-shaped bay was reversed when fillet beaches expanded upcoast of beach retention structures that were newly created downcoast of three groins. In three other instances hooked bay development was arrested by a seawall that extended downcoast past the LST region impacted by the groins. These results may be a basis for making planning level decisions on whether or not to utilize groins. They also provide background to check more rigorous functional design outcomes in environments like those discussed.
机译：在加利福尼亚南部，39个高，笔直，大多为海岸正常且显然不可渗透的腹股沟大部分都保留着比以前更大的上海岸海滩。百分之七十在腹股沟地区，有六个在沿海沙滩上引起问题。根据从航空照片中获得的这些腹股沟和相邻海滩的尺寸以及来自水准测量和波表的数据进行分析，并根据有效腹股沟长度，结构之间的间距，通过屈服指南来优化上海岸（鱼片）海滩的尺寸，腹股沟尖端对准，沉积物尺寸以及净和总的近岸沉积物输送速率。这些数据还有助于确定容易受到意外海岸冲击影响的位置，并指出减轻这些影响的选项。腹股沟在单位长度的结构中保留了最大的上海岸海滩，其中净长岸运输总比与长岸运输总比（LST）大，沉积物为沙粒大小（与砾石和鹅卵石相比），并且在LST逆转期间围绕结构运输的沉积物量为小。除了间距之外，腹股沟尖端相对于彼此以及相对于项目前海岸线的对齐方式还会影响腹股沟隔室中海滩的大小，方向和最靠近岸线的海岸线位置。 5（间距）与1（有效腹股沟长度）的平均比率（六个腹股沟区域）大于大多数经验法则建议。海滩变得越来越狭窄，其退入其财产的速度增加，鱼钩形海湾开始形成有效腹股沟的下海岸，其中：（1）每年的净LST超过约50,000立方米；（2）下海岸的海滩处于下陷状态；以及（3）沿结构尖端和与最接近的下海岸锚固结构邻接的海岸线之间的直线，波浪能通量有相当大的沿岸成分。当圆角滩扩展了沿岸保留结构的上海岸时，钩形海湾的演变被逆转了，而这种结构是由三个腹股沟新近产生的。在其他三个实例中，钩湾开发被海堤拦住了，海堤向腹股沟的影响下，向LST地区延伸了下海岸。这些结果可能是做出关于是否使用腹股沟的计划级别决策的基础。它们还提供了背景，以在所讨论的环境中检查更严格的功能设计结果。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号