The Effects of the Temporal-Spatial Distribution of Rainfall and Landslides on Suspended Sediment in Yu-Feng Catchment
Date Issued
2007
Date
2007
Author(s)
Chu, Yi-Ting
DOI
zh-TW
Abstract
本研究搜集颱風期間的短時距懸移質樣本，分析崩塌地的時空變化對石門水庫上游玉峰集水區2002年和2006年颱風事件的流量與懸移質濃度的關係影響。研究發現，單場颱風流量與懸移質濃度關係與臨前雨量、降雨特性和颱風發生時間有關，發生在颱風季節初期者遲滯效應不明顯，但出現在其他颱風之後者，其懸移質濃度與流量的關係則呈現順時針遲滯圈形態，顯示颱風事件末期輸砂供應不足的現象。此外，暴雨中心與主要崩塌地的相對關係，也與單場事件的懸移質濃度變化趨勢相吻合。
透過集水區崩塌地變遷分析，2002年至2006年這段期間崩塌地面積增加了2倍，且大多集中在河道附近，使2006年的懸移質濃度則較2002年增加了13.1~15.6倍。兩年的懸移質濃度在流量的上升翼和下降翼反應不一，2006年上升翼濃度增加速率比2002年快，下降翼減少速率則比2002年緩慢，顯示2006年懸移質供應量較充足，凸顯集水區崩塌地變遷對河川懸移質濃度變化的影響力。經由崩塌面積和對應的時雨量的時間序列乘積值，模擬出各場颱風事件懸移質濃度的變化趨勢，結果與實測值的趨勢變化相似，進一步印證崩塌地的位置和暴雨中心空間分布，對懸移質輸砂濃度變化的重要性。
Hourly water samples collected in Yu-Feng catchment, an upper montane catchment of Shihmen reservoir, from 7 typhoon events in 2002 and 2006 were used to construct hydrographs and time series of sediment concentration. It is found that the relationship between discharge and sediment concentration of an event were related to the antecedent rainfall, rainfall characteristics, and the timing of the events in the typhoon season. Hysteresis effect was less obvious when typhoons occurred in the beginning of the typhoon season, while typhoons which took place right after others showed clockwise hysteretic loops, indicating signs of sediment depletion in the catchment. Comparison of the landslide intensities at the loci of hourly rainfall centers in temporal sequence with the pattern of sediment concentration in the hydrographs verified the importance of landslides distribution in affecting the fluvial sediment concentration.
Comparisons of landslides records showed that landslide area increased two times from 2002 to 2006. It was found that the sediment concentration level in those 2006 typhoon events were 13.1 ~ 15.6 times of those in 2002. Sediment concentration in the rising limbs of those 2006 hydrographs increased with discharge at much higher rates than those of 2002 hydrographs. In contrast, sediment concentration in the falling limbs of those 2006 hydrographs decreased at much slower rates than those of 2002 hydrographs. These phenomena testified the existence of abundant sediment supply in 2006. The temporal-spatial relationship of the hourly rainfall centers and landslides and the temporal pattern of sediment concentration verified the importance of landslides distribution in affecting the sediment concentration of the river.
Subjects
颱風
崩塌
遲滯圈
懸移質
暴雨中心
typhoon
landslide
hysteretic loop
suspended sediment
rainfall center
Type
thesis
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