Sediment Transport Capacity in a Gravel-Bed River with a Sandy Tributary

Data Availability Statement: Data sharing is not applicable to this article.Copyright © 2023 by the authors. Bedload transport in a river is a deeply analyzed problem, with many methodologies available in the literature. However, most of the existing methods were developed for reaches of rivers rather than for confluences and are suitable for a particular type of material, which makes them very inaccurate in cases where the sediments are comprised of a mix of different types of soil. This study considers the effect of two different bed sediment sizes, gravel and sand, in relation to bed load transport in a confluence. Five well-known and validated equations (namely Meyer-Peter and Müller, Parker + Engelund and Hansen, Ackers and White, and Yang) are applied to the case study of the Tagus–Alberche rivers confluence (in Talavera de la Reina, Spain), where main and tributary rivers transport different materials (sand and gravel). Field works in the area of the confluence were conducted, and a set of alluvial samples were collected and analyzed. The previously mentioned methods were employed to analyze the geomorphology in the confluence area and downstream of it under different flooding scenarios, concluding different trends in terms of deposition/erosion in the area under historic flooding scenarios. When the trends show erosion, all methods are very consistent in terms of numerical predictions. However, the results present high disparity in the estimated values when the predictions suggest deposition, with Parker + Engelund and Hansen yielding the highest volumes and Meyer-Peter and Müller the lowest (the latter being around 1% of the former). Yang and Ackers and White predict deposits in the same range in all cases (around 15% of Parker and Engelund Hansen). Yang’s formula was found to be suitable for the confluences of rivers with different materials, allowing for the estimation of sediment transport for different grain sizes. The effect of different flow regimes has been analyzed with the application of Yang’s formula to the Tagus-Alberche confluence.This research received no external funding

Indicators of river system hydromorphological character and dynamics: understanding current conditions and guiding sustainable river management

The work leading to this paper received funding from the EU’s FP7 programme under Grant Agreement No. 282656 (REFORM). The Indicators were developed within the context of REFORM deliverable D2.1, therefore all partners involved in this deliverable contributed to some extent to their discussion and development

How wetlands affect floods

It is widely recognised that wetlands play an important role in the hydrological cycle, influencing groundwater recharge, low flows, evaporation and floods. This has led to policies being formulated world-wide to conserve and manage wetlands to deliver these key services, especially flood risk reduction. Generic statements have often been published about wetland hydrological services but the term “wetlands” covers many land types, including wet woodlands, reedbeds, peat bogs, fens, and salt marshes. Each of these wetland types can have a hydrological function that is subtly different, making it difficult to generalise the flood reduction services of wetlands. In this paper we focus on two example wetland types (upland rain-fed wetlands and floodplain wetlands) to demonstrate why there are differences in flood functions both within and between wetland types. Upland wetlands generally tend to be flood generating areas while floodplain wetlands have a greater potential to reduce floods. However, landscape location and configuration, soil characteristics, topography, soil moisture status and management all influence whether these wetlands provide flood reduction services

A GIS-based method for evaluating sediment storage and transport in large mining-affected river systems

Currently, the evaluation of sediment storage and transport for large river systems with variable flow has proven to be a challenge that often requires complex numerical models to be applied and sometimes costly direct data acquisition to be made. The present study proposes a low cost, widely available GIS-based method through which an initial assessment can be made on areas of sediment storage, transport and deposition as well as possible environmental risks that the accumulation of contaminated material may pose to riverine communities along the rivers’ channel. The method mainly relies on satellite imagery and elevation data to devise a quick model of the channel. The model has been successfully applied to study the Bolivian sector of the well-known mining-contaminated Rio Pilcomayo. The analysis shows that the portion of the channel from Villamontes to D’Orbigny accounts for more than half of the total c. 314 km2 sedimentation area of the Pilcomayo in Bolivia, and that the most environmentally problematic area is centreed around Puente Sucre, where agriculture is practiced on the contaminated floodplain. Combined with supplementary bathymetric data on the depth of the river in various points around the channel the method could offer further insight into the sediment fluxes and transport capacity of the Pilcomayo in various sectors and could thus be successfully used to assess other large mining-contaminated river channels around the world