Morphological assessment of reconstructed lowland streams in the Netherlands

Eekhout, Joris; Hoitink, A.J.F.; Brouwer, Jan H.F. de; Verdonschot, P.F.M.

doi:10.1016/j.advwatres.2014.10.008

Cited by 19 publications

(23 citation statements)

References 33 publications

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“…Other papers address some important open-questions concerning river's morphological models such as the implications due the correct estimate of the dominant discharge for assessing the river's morphological tendencies [12,14], the influence of riparian vegetation in the estimation of the bank erosion [4] and the importance of the hydrodynamic control targets in design procedure [9]. Particular attention is devoted to flow hydrodynamics in meandering bends [15,17].…”

Section: Discussionmentioning

confidence: 99%

“…This is to be expected somewhat, especially when hydrodynamic targets, which affect the main morphological response and the ecological status of the streams, are not adequately taken into account as design principles. This is discussed in the paper Morphological assessment of reconstructed lowland streams in the Netherlands [9] which presents a case of re-meandering as practice in restoring lowland streams.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

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Fluvial eco-hydraulics and morphodynamics: New insights and challenges

Termini

2015

Advances in Water Resources

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Section: Discussionmentioning

confidence: 99%

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

Fluvial eco-hydraulics and morphodynamics: New insights and challenges

Termini

2015

Advances in Water Resources

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“…The new channel was constructed with a width of 6.5 m, a depth of 0.4 m and a longitudinal slope of 0.96 m km −1 . A lowered floodplain surrounded the channel, with an average width of 20 m. The bed material mainly consists of fine sand, with a median grain size of 258 µm (Eekhout, 2014). Figure 1b shows the location of the study area in the catchment.…”

Section: Study Areamentioning

confidence: 99%

“…The first three surveys (days 0, 93 and 133) show the sequence of morphological changes that capture the chute cutoff event. The first DoD (day 0-93) shows deposition of sediment on the channel bed, which is associated with the formation of a plug bar (Eekhout, 2014). An initial embayment had formed upstream from the bend to be cutoff.…”

Section: Morphodynamicsmentioning

confidence: 99%

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Morphodynamic regime change in a reconstructed lowland stream

2014

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Abstract.With the aim to establish and understand morphological changes in response to channel reconstruction, a detailed monitoring plan was implemented in a lowland stream called Lunterse Beek, located in the Netherlands. Over a period of almost 2 years, the monitoring programme included serial morphological surveys, continuous discharge and water level measurements, and riparian vegetation mapping, from photographs and field surveys. Morphological processes occurred mainly in the initial period, before riparian vegetation developed. The initial period was largely dominated by upstream sediment supply, which was associated with channel incision upstream from the study area. Herbaceous vegetation started to develop approximately 7 months after channel reconstruction. The monitoring period included two growing seasons. A clear increase of riparian vegetation cover from first to the second year was observed. Detailed morphological and hydrological data show a marked difference in morphological behaviour between the pre-vegetation and post-vegetation stage. A linear regression procedure was applied to relate morphological activity to time-averaged Shields stress. In the initial stage after channel reconstruction, with negligible riparian vegetation, channel morphology adjusted, showing only a weak response to the discharge hydrograph. In the subsequent period, morphological activity in the channel showed a clear relation with discharge variation. The two stages of morphological response to the restoration measures may be largely associated with the upstream sediment supply in the initial period. Riparian vegetation may have played a substantial role in stabilizing the channel banks and floodplain area, gradually restricting the morphological adjustments to the channel bed.

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Chute cutoff as a morphological response to stream reconstruction: The possible role of backwater

Eekhout

Hoitink

2015

Water Resources Research

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Stream restoration efforts often aim at creating new unconstrained meandering channels without weirs and bank revetments. In reconstructed streams, the initial morphological response of the new streams is often rapid, until a dynamic equilibrium is reached. Here we report on a chute cutoff that occurred within 3 months after realization of a stream restoration project, caused by a plug bar that formed in response to a backwater effect. The temporal evolution of the morphology of both the new and the old channels was monitored over a period of nearly 8 months, including precutoff conditions. The observations can be separated into three stages. Stage 1 is the initial period leading to cutoff vulnerability, stage 2 is the actual cutoff, and stage 3 is the morphological adjustment in response to the cutoff. In stage 1, a plug bar was deposited in one of the channel bends. Hydrodynamic model results show the location of the plug bar coincides with a region where bed shear stress decreased in downstream direction due to backwater. Longitudinal channel bed profiles show that the channel slope decreased soon after channel reconstruction. Hence, sediment from upstream was available to form the plug bar. After the plug bar was deposited, an embayment formed in the floodplain at a location where the former channel was located (stage 2). The former channel was filled with sediment prior to channel construction. It is likely that the sediment at this location was less consolidated, and therefore, prone to erosion. The chute channel continued to incise and widen into the floodplain and, after 6 months, acted as the main channel, conveying the discharge during the majority of time (stage 3). The cutoff channel gradually continued to fill with sediment, from the moment the plug bar formed until the chute channel incised into the floodplain. Sedimentary successions of the deposited material show upward fining, which is in agreement with observations of chute cutoffs in rivers. Although the artificial setting limits the degree in which the observed processes can be projected on natural rivers, the observations prompt to investigate the role of backwater effects in natural chute cutoff initiation.

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Morphological assessment of reconstructed lowland streams in the Netherlands

Cited by 19 publications

References 33 publications

Fluvial eco-hydraulics and morphodynamics: New insights and challenges

Fluvial eco-hydraulics and morphodynamics: New insights and challenges

Morphodynamic regime change in a reconstructed lowland stream

Chute cutoff as a morphological response to stream reconstruction: The possible role of backwater

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