The object of this thesis to study the phenomena of sediment transport in
unsteady flow in the alluvial streams and the sediment transport relation
between the steady and the unsteady flow.
A mathematical model, named as "modified indirect method", is suggested to
simulate the sediment transport process in unsteady flow. The validity of
this model is examined by using both the flume data of unsteady movable
bed hydraulic experiments and the field data of Cho-Shui Chi (Hsilo
Bridge-Hsia Hai Chan). The results of this model are quite closed to the
flume data, but a some what deviate to the field data. Therefore, this
model is helpful for researcher to understand the unsteady sediment
transport process.
As planning a river training works, in general, the steady flow concept is
used. The how and the why to select a design discharge is an important
problem. In this thesis, the "equivalent steady discharge" is proposed as
a reference in selecting the design discharge. The "equivalent steady
discharge" reflects the main phenomean of the unsteady sediment transport
process in alluvial streams.
The amount of the "equivalent steady discharge" can be obtained from
theoretical analysis. The validity of the concept of "equivalent steady
discharge" is also checked with both the flume data and the filed data. It
is obvious that the concept and the calculated method of the equivalent
steady discharge has its pract6icality. It can be used for estimating not
only the total sediment yield in a flood process but also the design
discharge for river training works.
本文旨在研究沖積河川緩變量流輸砂現象及其與定量流輸砂現象間之關係。
首先，本文建議一變量流輸砂數學模式，稱之為「修正間接法」，用以模擬沖積河川
之緩變量輸砂過程。為驗證此一數學模式之可靠性，特進行一變量流動床水工試驗，
以實測之水位歷線為邊界條件進行數值演算，比較演算與實測之總輸砂量過程，演算
結果之水位歷線與實測值仍有差異，但仍能顯示變量流輸砂過程之主要現象。因此，
此一數學模式有助於研究者瞭解沖積河川之變量流輸砂過程。
其次，因河川治導工程一般均自定量流之觀點設計，故如何選擇一適當之設計流量為
一重要問題。在本文中建議一可顯示變量流輸砂過程之主要現象之定量流，稱之為相
當定量流，以為規劃河川治導工程時選擇設計流量之參考。
相當定量流之值可由理論分析求得。本研究並以變量流動床水工試驗及濁水溪下游段
之實測數據進行演算及比較，結果顯示本文建議之「相當定量流」之觀念及其值之推
算法，不僅可用於沖積河川洪水過程中總輸砂量及河床變動量之估算，且可用以估算
河川治導工程之設計流量。