從地形觀點談山區溪流的遊憩安全：以新北市大豹溪為例

Recreational Safety of the Mountainous River from the Geomorphic Perspective: A Case Study of the Dabao River, New Taipei City

游牧笛(Mu-Di Yu) ； 沈淑敏(Su-Min Shen)

《工程環境會刊》 35期 (2015/07) Pp. 103-120

https://doi.org/10.6562/JEE.2015.35.6

摘要

山區溪流風景宜人、空氣清新，盛夏時節常吸引遊客前往戲水消暑，但山區河道的地形水文特性多變，也潛藏著遊憩安全的威脅。本研究以大豹溪為例，從空間分析的角度，評估2000－2010年間溺斃事件和各河段的地形特性的關係，並以個案分析，推敲還有哪些因素不利於防止溺水意外演變為溺斃事件。研究結果顯示，大豹溪中下游段，多流經砂頁岩互層區，因其與流路的關係，常可見到厚層砂岩夾層凸出河岸，甚至幾乎橫亙河道，並常見巨礫分布。此種環境特性不但使河道較為崎嶇，也造成流速和水深多變化，而頁岩出露處則多濕滑，容易造成滑倒、溺水的意外，也常造成視線遮蔽，不利遊客互相照應或救生志工監看遊客行為。從河道地形潛在危害性和水岸易達性兩方面，評估出本研究區的18個子河段中，有7段較適合開放遊憩使用，有9段較不適合，而且其中6段具有高易達性。此外，根據溺斃事件最多之河段的個案分析，建議在選擇開放水域時，宜從整個河段的尺度考量，以避免遊客太容易接近潛在風險較高的水域。

關鍵字

山區溪流 ； 河道地形 ； 遊憩安全 ； 溺水事件 ； 大豹溪

並列摘要

Mountainous streams, with clear water, pleasing landscape and refreshing air, attract many visitors from big cities to escape the summer heat. The natural setting of the variable channel morphology and dynamic hydrology of the streams, however, is a threat to visitors. This study intends to analyze the recreational safety of the channel segments from the geomorphic perspective. A stretch of 10 km along the Dabou Stream is chosen as the study area due to its large number of reported drowning cases in the past. Results show that the characterized strata of interbedded sandstone and shale and the relationship of strata strike and river flow direction play important roles on shaping channel morphology along the study area. Where more resistant sandstone layers and ＞ 1 m boulders present, the channel profile become more rugged; while the channel reaches on less resistant shale beds, where usually pools located, are very slippery. Based on the degree of threats due to channel morphology and accessibility to the stream water, among 18 segments 7 are suitable and 9 are inappropriate for public recreational use. It is difficult for volunteer lifeguards to overlook visitors along a rugged channel, especially for those who deliberately explore the neighboring segments outside of the designated water areas by the local government. So, it is suggested that when considering suitability of open water areas, the unit of channel segment, but not just a smaller reach within, should be taken into account.

並列關鍵字

Mountainous Stream ； Channel Morphology ； Recreational Safety ； Drowning Events ； Dabou Stream