Three-Dimensional Investigation of Hydraulic Properties of Vertical Drop in the Presence of Step and Grid Dissipators

In irrigation and drainage channels, vertical drops are generally used to transfer water from a higher elevation to a lower level. Downstream of these structures, measures are taken to prevent the destruction of the channel bed by the flow and reduce its destructive kinetic energy. In this study, the effect of use steps and grid dissipators on hydraulic characteristics regarding flow pattern, relative downstream depth, relative pool depth, and energy dissipation of a vertical drop was investigated by numerical simulation following the symmetry law. Two relative step heights and two grid dissipator cell sizes were used. The hydraulic model describes fully coupled three-dimensional flow with axial symmetry. For the simulation, critical depths ranging from 0.24 to 0.5 were considered. Values of low relative depth obtained from the numerical results are in satisfactory agreement with the laboratory data. The simultaneous use of step and grid dissipators increases the relative energy dissipation compared to a simple vertical drop and a vertical drop equipped with steps. By using the grid dissipators and the steps downstream of the vertical drop, the relative pool depth increases. Changing the pore size of the grid dissipators does not affect the relative depth of the pool. The simultaneous use of steps and grid dissipators reduces the downstream Froude number of the vertical drop from 3.83–5.20 to 1.46–2.00.

Floating Debris in the Low Segura River Basin (Spain): Avoiding Litter through the Irrigation Network

The Vega Baja region lays on the lower course of the Segura River (southeastern Spain). It is one of the six traditional “huerta” European landscapes and has an ancient, extensive, and complex network of irrigation and drainage channels. The accumulation of floating waste causes numerous economic, environmental, and landscape problems in its irrigation infrastructures, hindering farmers’ water management practices. This work classifies and estimates the total volume of floating waste at various points along the Segura River and its irrigation channels as a first systematic approach to define and quantify the problem of floating waste accumulation. Aerial images taken by a drone were analyzed over time and a manual count of residues was performed on selected points. The results obtained show that reeds and residues of riparian vegetation represent more than 95% of the floating debris volume measured on the riverbed. Anthropogenic waste, which represents less than 5% of debris volume, was characterized, finding that plastics of domestic sources are the most abundant by count (14.9%) and only a reduced part of the floating waste can be attributed to agricultural activities (3.8%). Assessing the type and origin of the floating waste is essential to inform the actions required in order to avoid the floating waste reaching the Mediterranean Sea.

FLUVIAL LANDFORMS SEEN AS CAUSES OF THE DANUBE FLOODS CASE STUDY: OLTENITA - CALARASI SECTOR

<p>The aim of this paper is to analyze the fluvial landforms and to identify the main factors that influence the Danube floods. In this respect, we have performed a short analysis of the morphological and morphometric elements of the Danube Floodplain from the Oltenita - Calarasi area, of the wetlands and a correlation between these and the floods that have been cause. Finally, the current situation of embankments was assessed. For understanding the causes of floods in the studied area, two aspects should be taken into consideration: the morphometric and morphologic properties of the floodplain (low altitudes, low slope, low <a href="http://hallo.ro/search.do?l=ro&amp;d=en&amp;query=roughness">roughness</a>) and human intervention (drainage of the lakes and wetlands, harnessing measures like irrigation and drainage channels, lack of embankments rehabilitation).</p>