Adjustment of mainstream - Tributary relation upstream from a reservoir: An example from the Laohahe River, China

The long history of substantial human impacts on the landscape of the Mediterranean region, and their effects on fluvial systems, is documented. These effects have included impacts of deforestation and other land use changes, agricultural terracing on a wide scale, water transfers, and irrigation schemes. During the 20th century, major changes were made directly to channels through channelisation, construction of dams of various sizes, and extraction of gravel, and indirectly by reforestation. These changes have caused a major phase of incision on some rivers. Runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing. Some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material. The importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated. The analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects.

Human impacts on fluvial systems in the Mediterranean region (Invited paper for Binghamton Symposium

Sand mining, among the many activities that have significant effects on the bed changes of rivers, has increased in many parts of the world in recent decades. Numerical modeling plays a vital role in simulation in the long term; however, computational time remains a challenge. In this paper, we propose a sand mining component integrated into the bedload continuity equation and combine it with high-performance computing using graphics processing units to boost the speed of the simulation. The developed numerical model is applied to the Mekong river segment, flowing through Tan Chau Town, An Giang Province, Vietnam. The 20 years from 1999 to 2019 is examined in this study, both with and without sand mining activities. The results show that the numerical model can simulate the bed change for the period from 1999 to 2019. By adding the sand mining component (2002–2006), the bed change in the river is modeled closely after the actual development. The Tan An sand mine in the area (2002–2006) caused the channel to deviate slightly from that of An Giang and created a slight erosion channel in 2006 (−23 m). From 2006 to 2014, although Tan An mine stopped operating, the riverbed recovered quite slowly with a small accretion rate (0.25 m/year). However, the Tan An sand mine eroded again from 2014–2019 due to a lack of sand. In 2014, in the Vinh Hoa communes, An Giang Province, the Vinh Hoa sand mine began to operate. The results of simulating with sand mining incidents proved that sand mining caused the erosion channel to move towards the sand mines, and the erosion speed was faster when there was no sand mining. Combined with high-performance computing, harnessing the power of accelerators such as graphics processing units (GPUs) can help run numerical simulations up to 23x times faster.

Assessment of the Impact of Sand Mining on Bottom Morphology in the Mekong River in An Giang Province, Vietnam, Using a Hydro-Morphological Model with GPU Computing

It is necessary to understand the evolution of a river channel when reconstructing its evolution process and analyzing the controlling factors essential for river management and ecological restoration. In the past 50 years, the ecological environment around the Yongding River has deteriorated considerably, and the downstream has been completely cut off. Despite this, few have studied its morphology. In this study, we analyze the morphology of the Yongding River (Beijing, China) stretching for 92 km in four different periods between 1964 and 2018. A data treatment is carried out based on GIS, and the morphological evolution trajectory of the river channel at the overall and reach scales is reconstructed. The results show that the river morphology has undergone significant changes: the channel width has narrowed by 31%, and the temporal and spatial patterns show significant differences. By analyzing the impacts of human activities and climate change in various periods, we find human intervention to be the most important controlling factor. Based on our results, we proposed a set of river restoration strategies and protection measures for the Yongding River to guide watershed management and land planning.

https://www.mdpi.com/2073-4441/13/11/1489/pdf

Spatiotemporal Evolution Trajectory of Channel Morphology and Controlling Factors of Yongding River, Beijing, China

Controls of alluvial cover formation, morphology and bedload transport in a sinuous channel with a non-alluvial boundary

Channel adjustments in the lower Guadalquivir River (southern Spain) over the last 250 years

An overall hydromorphological assessment of the middle to lower Guadalquivir River (southern Spain) was conducted using the Morphological Quality Index (MQI) and a novel extension, the Hydro-Morpho...

An assessment of the hydromorphological conditions of the middle and lower Guadalquivir River (southern Spain)

Hydrological and geomorphic effects upstream of the Cantillana Dam along the Guadalquivir River (southern Spain)

The spatial distribution of land use and soil loss in the hydrographic sub-basin of the Oued Ourtza (Eastern Prerif, Morocco) between 2000 and 2014 is the subject of this study. We have extracted the thematic information from satellite imagery for the mapping of land occupation and then used geographic information systems for the spatialisation of water erosion according to the universal equation for soil loss in its version adapted to Mediterranean conditions. The resulting maps show an increase in the areas of arboriculture and a significant abandonment of land (36.8 %). The soil losses are quite high (40 t·ha -1 ·yr -1 ) and well above the tolerance threshold; although they are similar to ablation rates in some areas of the Mediterranean environment and the Moroccan Rif. These losses are unevenly distributed, with the highest rates corresponding to uncultivated or abandoned land (>80 t·ha -1 ·yr -1 ) whose extension continues to increase, especially in the middle and lower reaches of the sub-basin where fragile materials dominate.

/pdf/evaluacion-de-los-usos-del-suelo-y-la-erosion-hidrica-en-la-31xuq1n4if.pdf

Inmaculada C. Guerrero-Amador

Papers

Channel adjustments in the lower Guadalquivir River (southern Spain) over the last 250 years

An assessment of the hydromorphological conditions of the middle and lower Guadalquivir River (southern Spain)

Hydrological and geomorphic effects upstream of the Cantillana Dam along the Guadalquivir River (southern Spain)

Evaluación de los usos del suelo y la erosión hídrica en la subcuenca hidrográfica montañosa del Oued Ourtza (Pre-Rif Oriental, Marruecos)