Sediment transport in intermittent mountainous rivers and streams

Duration: 2013.04.01 to 2021.12.31
Department: LWW

Abstract

Rivers and streams that are characterized by flow, sediment transport, and habitat seasonality are termed as intermittent rivers. Intermittent rivers and streams (IRS) are the main water bodies in arid and semi-arid regions; however, they are also found in temperate and humid environment where they in particular drain headwater streams. Thus a large part of headwater streams in mountainous regions have a similar characteristic as intermittent water bodies where the steep channel slope and a wide variety of sediment sizes contribute to their hydro morphological complexity.
Despite the fact that IRS drain about 40% of the terrestrial area worldwide, their hydro- morphological characteristics are not well understood. Existing knowledge gaps represent a challenge in terms of sustainable management of IRS and often, the experience and knowledge of perennial rivers are adapted to IRS, which may lead to serious problems. Premature sedimentation of reservoirs and in irrigation channels in arid and semi-arid regions are examples of problems occurring as a result of incomplete knowledge and lack of experience in predicting sediment transport in IRS. In case that the channel slope in lowland perennial rivers is adapted to steep IRS, the sediment transport rates may be largely overestimated, which in turn can lead to inaccurate sediment management of rivers and reservoirs.
Therefore, the main objective of this dissertation is to investigate the sediment transport in mountainous intermittent rivers and streams. A regime channel approach is employed in a series of 2D- hydro- morphological models to understand the relationship of channel regime slope, flow resistance, and sediment transport. The initial results show that mountain IRS develop larger resistance to flow, which in turn reduces the effect of steep slopes on sediment transport. The ultra-high flow resistance in steep IRS is developed by coarse riverbed sediments, macro-roughness elements (i.e., cobbles and boulders) and their arrangement in step-pool and cascade bedforms.
The relationship between channel slope and flow resistance derived by fulfilling the regime conditions can be effectively utilized to predict sediment transport and to avoid overestimation of sediment transport in IRS.

Project manager

Deputy

Research assistants

Najibullah Sadid

Department

Duration

From: 2013.04.01

To: 2021.12.31

Finances

Scholarship - German Academic Exchange Service (DAAD)

 

directions

Pfaffenwaldring 61, 70569 Stuttgart, Germany

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