Assessing riparian zone impacts on water and sediment movement: a new approach

Keesstra, S. D. and Kondrlova, E. and Czajka, A. and Seeger, M. and Maroulis, J. (2012) Assessing riparian zone impacts on water and sediment movement: a new approach. Netherlands Journal of Geosciences, 91 (1/2). pp. 245-255. ISSN 0016-7746

Abstract

The state of river channels and their riparian zones in terms of geomorphology and vegetation has a significant effect on water and sediment transport in headwater catchments. High roughness in natural rivers due to vegetation and geomorphological attributes generate drag on flowing water. This drag will slow water discharge, which in turn influences the sediment dynamics of the flow. The impacts of changes in the management of rivers and their riparian zone (either by catchment managers or river restoration plans) impacts both up- as well as downstream reaches, and should be assessed holistically prior to the implementation of these plans.
To assess the river's current state as well as any possible changes in geomorphology and vegetation in and around the river, effective approaches to characterise the river are needed. In this paper, we present a practical approach for making detailed surveys of relevant river attributes. This methodology has the benefit of being both detailed – describing river depth, width, channel morphology, erosive features and vegetation types – but also being practical in terms of time management. This is accomplished by identifying and describing characteristic benchmark reaches (typical sites) in detail against which the remainder of the river course can be rated. Using this method, a large river stretch can be assessed in a relatively short period while still retrieving high quality data for the total river course. In this way, models with high data requirements for assessing the condition of a river course, can be parameterised without major investments on field surveys.
In a small headwater catchment (23 km2) in southwestern Poland, this field methodology was used to retrieve data to run an existing model (HEC-GeoRAS) which can assess the impact of changes in the riparian and channel vegetation and channel management on sedimentation processes and stream flow velocity. This model determines the impact of channel morphology and in-channel and riparian vegetation on stream flow and sediment transport. Using four return periods of flooding (2, 10, 20 and 100 years), two opposing channel management / morphology scenarios were run; a natural channel and a fully regulated channel. The modelling results show an increase in the effect of riparian vegetation / geomorphology with an increase in return period of the modeled peak discharge. More natural channel form and increased roughness reduces the stream flow velocity due to increasing drag from flow obstructions (vegetation and channel morphological features). The higher the flood water stage, the greater the drag due to vegetation on the floodplains of natural river reaches compared to channelised sections. Slower flow rates have an impact on sediment mobilisation and transport in the river.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © Stichting Netherlands Journal of Geosciences is registered with the Copyright Clearance Center (CCC), 222 Rosewood Drive, Danvers, MA 01923, USA. Authorization to photocopy items for internal or personal use is granted by the Stichting Netherlands Journal of Geosciences, provided that the appropriate fee is paid directly to CCC. Prior to photocopying, please get permission online at the CCC website (http://www.copyright.com ) or call the CCC (+1 978 750 8400), which can also be contacted for information about additional usage of material.
Faculty / Department / School: Current - USQ Other
Date Deposited: 18 Apr 2013 23:58
Last Modified: 08 Feb 2018 07:06
Uncontrolled Keywords: riparian vegetation; water and sediment transport; channel management; modelling flood retention
Fields of Research : 04 Earth Sciences > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology
09 Engineering > 0907 Environmental Engineering > 090702 Environmental Engineering Modelling
04 Earth Sciences > 0406 Physical Geography and Environmental Geoscience > 040601 Geomorphology and Regolith and Landscape Evolution
Socio-Economic Objective: D Environment > 96 Environment > 9605 Ecosystem Assessment and Management > 960506 Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments
D Environment > 96 Environment > 9609 Land and Water Management > 960999 Land and Water Management of Environments not elsewhere classified
Identification Number or DOI: 10.1017/S0016774600001633
URI: http://eprints.usq.edu.au/id/eprint/23049

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