Flow Patterns and Morphological Changes in a Sandy Meander Bend during a Flood—Spatially and Temporally Intensive ADCP Measurement Approach

Elina Kasvi,Leena Laamanen,Petteri Alho,Eliisa Lotsari

doi:10.3390/w9020106

Elina Kasvi, Leena Laamanen + Show 2 more

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https://doi.org/10.3390/w9020106

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Abstract

The fluvio-geomorphological processes in meander bends are spatially uneven in distribution. Typically, higher velocities and erosion take place near the outer bank beyond the bend apex, while the inner bend point bar grows laterally towards the outer bank, increasing the bend amplitude. These dynamics maintain the meander evolution. Even though this development is found in meandering rivers independent of soil or environmental characteristics, each river still seems to behave unpredictably. The special mechanisms that determine the rate and occasion of morphological changes remain unclear. The aim of this study is to offer new insights regarding flow-induced morphological changes in meander using a novel study approach. We focused on short-term and small-spatial-scale changes by conducting a spatially and temporally (daily) intensive survey during a flood (a period of nine days) with an ADCP attached to a remotely controlled mini-boat. Based on our analysis, the flood duration and the rate of discharge increase and decrease seems to play key roles in determining channel changes by controlling the flow velocities and depth and the backwater effect may have notable influence on the morphological processes. We discuss themes such as the interaction of inner and outer bend processes and the longer-term development of meander bends.

Highlights

Morphological processes in rivers may have significant effects on both the environment and society
The field-based studies of river dynamics have been mostly realized along series of cross-sections over the river, the locations of which depended on the research question [1,2,3,4,5]
This study demonstrated the application of a remotely controlled mini-boat equipped with an ADCP device and high accuracy GNSS to investigate short-term and small-scale flow and sediment dynamics in a meander bend during a flood

Summary

Introduction

Morphological processes in rivers may have significant effects on both the environment and society. The fundamental theories of the meander bends fluvio-geomorphology are based on intensive cross-section based field studies performed during 1970s and 1980s [1,2,6,7,8,9,10,11]. These studies provided a strong basis for the understanding of the complex processes of meander bends and, this period was followed by a relatively quiet era in field-based meandering research.

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