七家灣溪集水區之漂流木基本特性及空間分佈狀態

Essential Characteristic and Spatial Distribution of Large Woody Debris in Chiachiwan Watershed

10.29417/JCSWC.201012_41(4).0003

陳樹群(Su-Chin Chen)；趙益群(Yi-Chin Chao)

七家灣溪集水區 ； 漂流木 ； 蓄積量 ； 河川型態 ； Chichiawan creek catchment ； large woody debris LWD ； accumulation volume ； river morphology

中華水土保持學報

41卷4期（2010 / 12 / 01）

308 - 318

繁體中文

七家灣溪集水區河道內之漂流木多屬於邊坡崩塌等因素所產生。本研究探討該區漂流木之基本特性、空間分佈及在河道中所扮演之角色；這些漂流木大多以樹幹(73%)而且爲單根(71%)之形式散佈於河道中。河道中之漂流木多數散佈於河岸邊緣(75~95%)，其次爲江心洲(1~24%)，少部份在河道中(1~2%)或以橫跨河道(3%)出現。高山溪河道主要係由堅硬之岩盤所組成之狹窄河道，所以尺寸較大之漂流木易阻塞於河道中；但是相對地，該處河床坡度較大，漂流木易被輸送至下游。河寬較寬且有復列沙洲存在之河道，河床坡度相對較小，漂流木容易散佈於沙洲上。這也是高山溪河道內之漂流木蘊藏量(20立方公尺/100m)大於桃山溪及七家灣溪（15及13立方公尺/100m）；但是，漂流木出現之頻率卻遠小於其他兩個河段之原因。

The large woody debris (LWD) in the Chichiawan Creek is the result of landslides. This study explores the essential characteristics, spatial distribution, and the function of LWD in the Chichiawan Creek. Most of the LWD are trunks (73%) which disperse as single pieces (71%) in the channel. The highest percentage of LWD disperse on the channel margins (75~95%), following the percentage of LWD present on the sandbar (1~24%), and a small amount appears in the channel (1~2%) or across the channel (3%). The Gaoshan Creek is a narrow channel composed of hard bedrock. Therefore, the large LWD blocked up easily in the channel. However, the steep slope facilitates the transport of LWD downstream. The LWD tends to disperse on the wider and braided channel because of the mild slope. These are the reasons the Ganshan Creek (20 m^3/100m) has a higher quantity of LWD then those in the Taoshan Creek and the Chichiawan Creek (15 and 13 m^3/100m, respectively). However, the abundance of LWD in Gaoshan Creek is less than that of the others.