ORCID Profile
0000-0001-9996-8975
Current Organisations
University of Hull
,
Universidade Federal do Paraná
,
Universitas Negeri Malang
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Publisher: Wiley
Date: 21-08-2021
DOI: 10.1002/ESP.5177
Abstract: With riverine flooding set to be more frequent in many parts of the world as a result of climate change, the interactions between fluvial morphodynamics and riparian vegetation may depend in part on the sequence of flood events. This paper describes a laboratory study of the geomorphic adjustment of a braided river to sequences of floods across five different strengths of braidplain vegetation. By using alfalfa as a proxy for braidplain vegetation, the differing plant life stages were used to represent the varying strengths of biogeomorphic feedbacks across the floods. Boundary conditions were constrained by sets of experimental runs with both equilibrium sediment loads and deficit loads. Changes in bed topography were monitored and assessed using a detailed digital elevation model, digital imagery and continuous monitoring of the transported sediment. Results demonstrate that in absence of plant colonization, vegetation placed the rivers in a non‐equilibrium condition, in which riparian vegetation encouraged the development of new channels, increased the system channel width and enhanced topographic irregularity, these effects being more noticeable during the low‐flow periods. The morphodynamics was found to be less sensitive to variations in flood discharges as the vegetation influence (strength) increased from minimum to maximum, until vegetation began to die back and the impacts of flood sequences became yet again evident. Although the overall sediment transport rate was reduced under full‐grown vegetation conditions, the presence of the mature plants across the braid bars resulted in the greatest channel scour depths. Results are considered in light of expected changes in flood frequency with climate and likely morphodynamic responses of river systems as a result.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-18431
Abstract: & & Sequential observations of channel adjustments in relation to short-term flow variability are required to evaluate the effects of temporal ordering of hydrologic events on channel form. With the increasing hydroclimate variability due to global climate change, fluvial morphology might also exhibit adjustments toward changing equilibria. By combining flume and numerical modelling we examine the mechanism of bed morphology changes of braided rivers to a sequence of low to moderate magnitude flood events. Over 60 runs were performed in a mobile bed flume (10 m x 2.5 m), with constant longitudinal slope (0.015) and mean grain size (0.45 mm) in the Total Environment Simulator at the University of Hull, UK. The outcomes of each run were characterized by a detailed digital elevation model, digital imagery and continuous monitoring of the sediment transported through the flume outlet. Sediment conditions included floods with equilibrium and deficit loads. Rivers were allowed to evolve from an initially flat-bed to a self-organized, steady state. The rate of change and rate of bed load movement against time were indicative of the gradual approach to equilibrium. The Delft3D code in depth-averaged (2-D) mode was used to reproduce different aspects of the braiding process over an up-scaling of the laboratory river. Data analysis allowed us to assess the effect of discharge variation on the braiding dynamics and on the width-to-depth ratio of channels, which although variable in time, fluctuated among defined values. Once in equilibrium, net changes in reach-averaged width and depth values were relatively minor. The adjustment of the river morphology through time was well fitted by an exponential decay expression, and we tested diffusive relationships held within our braided river system for both constant and varying discharge conditions. In long term process-response systems, climatic changes introduce sequences of disruption of equilibria such as those analysed in this study. The results might provide then a useful basis for analysing the similar but more complex long-term dynamics found in natural rivers.& & & & & & &
Publisher: Springer Science and Business Media LLC
Date: 21-06-2022
DOI: 10.1038/S41598-022-14569-0
Abstract: Ponds are often identified by their small size and shallow depths, but the lack of a universal evidence-based definition h ers science and weakens legal protection. Here, we compile existing pond definitions, compare ecosystem metrics (e.g., metabolism, nutrient concentrations, and gas fluxes) among ponds, wetlands, and lakes, and propose an evidence-based pond definition. Compiled definitions often mentioned surface area and depth, but were largely qualitative and variable. Government legislation rarely defined ponds, despite commonly using the term. Ponds, as defined in published studies, varied in origin and hydroperiod and were often distinct from lakes and wetlands in water chemistry. We also compared how ecosystem metrics related to three variables often seen in waterbody definitions: waterbody size, maximum depth, and emergent vegetation cover. Most ecosystem metrics (e.g., water chemistry, gas fluxes, and metabolism) exhibited nonlinear relationships with these variables, with average threshold changes at 3.7 ± 1.8 ha (median: 1.5 ha) in surface area, 5.8 ± 2.5 m (median: 5.2 m) in depth, and 13.4 ± 6.3% (median: 8.2%) emergent vegetation cover. We use this evidence and prior definitions to define ponds as waterbodies that are small ( 5 ha), shallow ( 5 m), with 30% emergent vegetation and we highlight areas for further study near these boundaries. This definition will inform the science, policy, and management of globally abundant and ecologically significant pond ecosystems.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Rocio Luz Fernandez.