Channel Morphology Responses to Rock-uplift Behavior along Daan River, Central Taiwan
Date Issued
2009
Date
2009
Author(s)
Lai, Yi-Jing
Abstract
The variations of bedrock channel morphology, such as channel width and slope, have been proposed to reflect the different incision rate. On the other hand the incision rate has been suggested to be equal to the rock-uplift rate when the river longitudinal profile is in steady state. This study aims at understanding and deriving the relative local rock-uplift rate along a river by observing the changes of its bedrock channel morphology. In central Taiwan Daan River transverses a series of N-striking structures such as Tienkou fault, Tungshih anticline, and Chentoushan fault and gives a good opportunity to examine the channel dynamics across these structures. Using a 40m digital elevation model and 1/5000 and 1/10000 Orthophoto Base Maps and measuring rock strength, this study obtained the channel width, slope, drainage area, and rock strength along the Daan River and figured out the relationship to the relative activities of structures. This study also built the hydraulic empirical functions of Daan River, and further combined them with shear stress model in steady state to calculate the steepness index (ks) and discuss the correlation between ks and rock-uplift rate. ccording to the results, the channel morphology dose not relate to lithology along Daan River, but the anomaly variations of channel morphology are influenced by structures. The abrupt changes in channel width and slope indicate the Tienkou fault, Shuangchi fault, Tungshih anticline, and Chentoushan fault have relatively higher activities. The exponents of hydraulic empirical functions are similar to the previous studies, and further the concavity index (θ) of Daan River is nearly the same as the θ modeled in the steady state, indicating Daan river is in steady state. From the results, the channel slope is less relative to structures, and it might result from three factors. First, the timing of the changes of channel slope and width to adjust the incision rate is not the same. Second, to preserve the variations of channel slope is more difficult than channel width. Third, the elevation accuracy of DEM has deeper influence on the channel slope than on the channel width. Furthermore the ks dose not respond to these structures implied as active strucutres, except Tienkou fault. Because the ks is derived from the channel slope without involving the width, further studies should combine the steepness index (ks) with width coefficient (kw), which could better represent the rock -uplift rate.
Subjects
shear stress model
channel width
channel slope
steepness index (ks)
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-R96224103-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):62a27ce2e5c2972f3957f15c5306db01