Effects of different weed cutting methods on physical and hydromorphological conditions in lowland streams

Rasmussen, Jes J.; Kallestrup, Helena; Thiemer, Kirstine; Alnøe, Anette Baisner; Henriksen, Lisbeth D.R.; Larsen, Søren E.; Baattrup‐Pedersen, Annette

doi:10.1051/kmae/2021009

Cited by 10 publications

(4 citation statements)

References 41 publications

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“…The limited residence times under non-vegetated conditions (Fig. 6) decrease the likelihood for in-stream retention and may manifest as increased nitrate (Soana et al, 2019) and suspended sediment loads (e.g., Biggs et al, 2021;Rasmussen et al, 2021) to downstream water bodies after extensive cutting. In addition to decreasing in-stream retention, vegetation removal may increase erosion and mobilisation of e.g.…”

Section: Implications Of Vegetation Maintenance On Pollutant Managementmentioning

confidence: 99%

Influence of vegetation maintenance on flow and mixing: case study comparing full cut with high-coverage conditions

Kalinowska

Västilä

Nones

et al. 2022

Preprint

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Abstract. In temperate climates, agricultural ditches are generally bounded by seasonal vegetation, which affects the hydrodynamics and mixing processes within the channel and acts as a buffer strip to reduce a load of pollutants coming from the surrounding cultivated fields. However, even if the control of such vegetation represents a key strategy to support sediment and nutrient management, the studies that investigated the effect of different vegetation maintenance scenarios or vegetation coverage on the flow and mixing dynamics at the reach scale are very limited. To overcome these limitations and provide additional insights on the involved processes, tracer tests were conducted in a 500 meters long agricultural ditch close to Warsaw in Poland, focusing on two different vegetation scenarios: highly vegetated and fully cut. Additionally, under the highly vegetated scenario, sub-reaches differing in surficial vegetation coverage are analysed separately to understand better the influence of the vegetation conditions on the flow and mixing parameters. Special attention has been paid to the longitudinal dispersion coefficient in complex natural conditions and its dependency on vegetation coverage (V). The vegetation maintenance decreased the travel and residence times of the solute by 3–5 times, moderately increasing the peak concentrations. We found that the dispersion coefficient decreased approximately linearly with the increase of vegetation coverage at V>68 %. Further research is needed at lower vegetation coverage values and different spatial plant distributions. The obtained longitudinal dispersion coefficient values complement the previously published data, which are barely available for small natural streams. The new process understanding supports the design of future investigations with more environmentally sound vegetation maintenance scenarios.

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Section: Implications Of Vegetation Maintenance On Pollutant Managementmentioning

confidence: 99%

Influence of vegetation maintenance on flow and mixing: case study comparing full cut with high-coverage conditions

Kalinowska

Västilä

Nones

et al. 2022

Preprint

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“…Thus, radical removal of aquatic vegetation may have unforeseen negative consequences when such services are reduced or no longer provided. However, the strength of the functional relations between vegetation and ecosystem services is not necessarily generalizable across ecosystems (Carpenter & Lodge, 1986; Hilt et al., 2017; Rasmussen et al., 2021). For example, some species are more efficient in nutrient uptake than others (Denny, 1972) and some species are more readily eaten by herbivores than others (Bakker et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

Mass development of aquatic plants: Effects of contrasting management scenarios on a suite of ecosystem services

Vermaat,

Thiemer,

Immerzeel

et al. 2023

Journal of Applied Ecology

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Dense beds of aquatic plants are often perceived as nuisance and therefore mechanically removed, often at substantial cost. Such removal, however, may affect a range of ecosystem functions and consequently also the ecosystem services that benefit society. We studied five cases: River Otra (Norway), River Spree (Germany), Lake Kemnade (Germany), Lake Grand‐Lieu (France) and Hartbeespoort Dam (South Africa). In all, nuisance aquatic plant growth is managed, but dominant species, geographic setting and major societal uses are different. We quantified 12 final ecosystem services as flows per area and year in biophysical and monetary terms. Quantified services were food and fodder production, commercial fisheries, hunting and gathering wild products, hydropower production, drinking and irrigation water production, flood prevention, carbon sequestration, active and passive recreation and biodiversity conservation (nonuse). These services were related to aquatic plant cover via a range of ecosystem functions, and the effects were estimated of three plant removal regimes on the relative importance of the quantified ecosystem services and on the total sum of the monetary estimates (total economic value, TEV). The three removal regimes were ‘maximum removal’, ‘current practice’ and ‘do nothing’. In all five cases, TEV was dominated by different forms of recreation. TEV was highest for Lake Kemnade, where visitor densities were highest. TEV was most sensitive to the different management regimes in Lake Kemnade, because a threshold in aesthetic appreciation was passed in the ‘do‐nothing’ regime, and in Hartbeespoort Dam, because of the effect on boating and angling. In the other cases, the different removal regimes had little effect on the estimated TEV. Synthesis and applications. Since recreation dominated the estimated societal benefits in the studied ecosystems, also where provision of hydropower, drinking water or irrigation water were relevant, effects on recreation should be a core consideration in the management of nuisance aquatic plants. Furthermore, aquatic plant management strategies will benefit from taking into account the differences in perceived nuisance among different categories of recreative users before engaging in costly removal.

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“…In particular, plant patches could be favourable in human-impacted rivers requiring environmental improvements but disallowing natural recovery or full restoration because of flood management, irrigation and drainage, hydropower, recreational activities or disease control (González del Tánago et al, 2021;Thiemer et al, 2021). To support these human purposes, vegetation is currently widely removed from river and floodplain areas as part of routine maintenance, with the ecologically harmful complete removal through cutting still common (Rasmussen et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…In particular, plant patches could be favourable in human‐impacted rivers requiring environmental improvements but disallowing natural recovery or full restoration because of flood management, irrigation and drainage, hydropower, recreational activities or disease control (González del Tánago et al, 2021; Thiemer et al, 2021). To support these human purposes, vegetation is currently widely removed from river and floodplain areas as part of routine maintenance, with the ecologically harmful complete removal through cutting still common (Rasmussen et al, 2021). As an alternative, maintaining patchy vegetation presents an intermediate solution between naturally vegetated and fully cut conditions and potentially allows optimizing between flow conveyance and water quality targets by influencing the flow resistance, dispersion, residence times and retention of soluble and particulate matter as analysed by Bal et al (2011) and Verschoren et al (2017) regarding aquatic plants.…”

Section: Introductionmentioning

confidence: 99%

Longitudinal dispersion affected by willow patches of low areal coverage

Västilä

Sonnenwald

et al. 2022

Hydrological Processes

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Vegetation notably influences transport and mixing processes and can thus be used for controlling the fate of substances in the hydro-environment. Whilst most work covers fully vegetated conditions, the novelty of this paper is to focus on flows with real-scale flexible willow patches. We aimed to investigate how longitudinal dispersion varies according to the spatial distribution, density and coverage of the patches and to evaluate the explanatory power of predictors that consider the hydraulics, vegetation and channel geometry. Salt tracer experiments were performed in a trapezoidal channel where we established 3-4 m long and 1-1.6 m wide patches of artificial foliated willows that reproduced the shapes and plant densities observed on woody-vegetated floodplains. We examined sparsely distributed patches with low areal/volumetric coverage of 6-11%, and non-vegetated conditions for reference.Flow depths and surface widths were 0.7-0.9 and 6-7 m, respectively, and the mean flow velocities ranged at 0.3-0.6 m/s. The emergent patches generated from a negligible to over a four-fold increase in the longitudinal dispersion when compared with non-vegetated conditions. The patches with a preferential location in low-velocity areas, such as near banks, or with a high plant density and a blockage of the crosssectional flow area ⪆0.4, led to the largest dispersion and residence times. Patches under such configurations enhanced the normalized differential velocity defined as the difference between the highest (90th percentile) and lowest (10th percentile) cross-sectional flow velocities divided by the mean velocity, thus increasing shear dispersion. As existing analytical predictors failed to estimate the effect of different patch configurations, we proposed the change in the normalized differential velocity between vegetated and corresponding non-vegetated conditions as a basic predictor of the reach-scale longitudinal dispersion coefficient under patchy vegetation. In contrast, we observed no clear relationship between flow resistance and dispersion. Thus, our findings indicated that bankside vegetation may allow for reduced peak concentrations and lengthened residence times, supporting pollutant management, while ensuring good flow conveyance. Such rare field-scale analyses improve the estimation of solute transport in real vegetated flows.

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Effects of different weed cutting methods on physical and hydromorphological conditions in lowland streams

Cited by 10 publications

References 41 publications

Influence of vegetation maintenance on flow and mixing: case study comparing full cut with high-coverage conditions

Influence of vegetation maintenance on flow and mixing: case study comparing full cut with high-coverage conditions

Mass development of aquatic plants: Effects of contrasting management scenarios on a suite of ecosystem services

Longitudinal dispersion affected by willow patches of low areal coverage

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