Coastal infrastructure projects, particularly the modification of coastal river channels, are becoming increasingly significant to economic activities worldwide as a response to climate-driven changes and urbanization. The benefits of channel modification projects can be realized quickly, but the altered movement of sediments in the river channel can lead to unintended geomorphic changes years or decades later. An example of this is the closure of the San Bernard River mouth, located on the central coast of Texas, which was clogged with sediments by the 1990s as a result of two major projects in the area: the diversion of the Brazos River channel (1929) and the construction of the Gulf Intracoastal Waterway (GIWW) (1940s). The objective of this study was to a) document the delayed geomorphic response to the projects using a GIS analysis of historical maps and aerial imagery, and b) provide a snapshot of altered flow pathways in the area using measurements collected in situ. Results showed that the GIWW was the main conduit for river flow as it bisects the San Bernard River 2 km inland of its river mouth, reducing discharge in the terminal limb of the river. Due to reduced flow, the river mouth became clogged with wave-transported sediment supplied by the still-adjusting Brazos River which had been diverted to within 6 km of the San Bernard River. With a limited connection to the sea, altered sediment and flow pathways have led to numerous hazards and costly corrective dredging projects surpassing $12 million to date. Optimizing the cost-effectiveness of channel modification projects requires considering their long-term impact as managers continue to adapt to ever-changing coastal zones.

中文翻译：

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改造沿海河流系统的意外后果


作为对气候驱动的变化和城市化的回应，沿海基础设施项目，特别是沿海河道的改造，对全球经济活动变得越来越重要。河道改造项目的好处可以很快实现，但河道中沉积物运动的改变可能会导致数年或数十年后意外的地貌变化。这方面的一个例子是位于德克萨斯州中部海岸的圣伯纳德河河口的关闭，由于该地区的两个主要项目，到 1990 年代，该河口被沉积物堵塞：布拉索斯河航道的改道（1929 年）和海湾内陆水道 （GIWW） 的建设（1940 年代）。本研究的目的是 a） 使用历史地图和航空图像的 GIS 分析来记录对项目的延迟地貌响应，以及 b） 使用现场收集的测量值提供该地区改变的水流路径的快照。结果表明，GIWW 是河流流动的主要渠道，因为它将圣伯纳德河在其河口内陆 2 公里处一分为二，减少了河流末端的排放。由于流量减少，河口被仍在调整的布拉索斯河 （Brazos River） 提供的波浪输送沉积物堵塞，该沉积物已改道至圣伯纳德河 6 公里范围内。由于与海洋的联系有限，沉积物和水流路径的改变导致了许多危险和昂贵的纠正性疏浚项目，迄今为止已超过 1200 万美元。优化航道改造项目的成本效益需要考虑其长期影响，因为管理人员要继续适应不断变化的沿海地区。