Estimation of discharges of water flows and debris floods in a small watershed

2020 ◽  
Author(s):  
Xiaojun Guo ◽  
Peng Cui ◽  
Xingchang Chen ◽  
Yong Li ◽  
Ju Zhang ◽  
...  
Keyword(s):  
Small Watershed ◽  
Water Flows ◽  
Debris Floods

Sediment-water flows in mountain catchments: Variability in response to high-magnitude hydrological events

2021 ◽  
Author(s):  
Andrea Brenna ◽  
Marco Borga ◽  
Massimiliano Ghinassi ◽  
Lorenzo Marchi ◽  
Mattia Zaramella ◽  
...  
Keyword(s):  
Debris Flow ◽  
Water Flow ◽  
Debris Flows ◽  
Transport Mechanisms ◽  
Stream Network ◽  
Water Flows ◽  
High Magnitude ◽  
Sediment Transfer ◽  
Flood Deposits ◽  
Debris Floods

<p>Sediment transfer in mountain streams occurs by processes classified as debris flows, hyperconcentrated flows, debris floods, and water flows. One of the most important tasks in investigating floods in mountain catchments is to identify the transport mechanisms since different sediment-water flows induce peculiar geomorphological dynamics and hazards. This study aims at testing how the energy of water and the amount of sediment involved during a high-magnitude hydrological event can modify the mechanisms of sediment transfer with respect to those occurring during ordinary floods.</p><p>The selected case study is the Tegnas catchment (Dolomites, Italy), which, in October 2018, was affected by a severe hydrological event (Vaia Storm) with a recurrence interval of about 200 years. The studied catchment drains an area of 51 km<sup>2</sup>, with a range in elevation between 2872 and 620 m a.s.l.. The classification of flows that occurred during the Vaia storm was addressed at the sub-reach scale applying a field survey protocol developed to classify the flood deposits based on their sedimentological and morphological features. Following the same approach, we also determined the flow types typifying the stream network during ordinary floods. Additionally, we considered flows predicted by three morphometric approaches for high-magnitude events, and took into account the geomorphological dynamics (e.g., channel changes) and the hydraulic constraints (i.e., unit stream power) that occurred during the Vaia storm.</p><p>Water flow was the dominant process during Vaia storm in the Tegnas main steam (12 sub-reaches), although debris flow and debris flood deposits were documented at 3 and 7 sub-reaches, respectively. Water flow was observed in response to ordinary events along the entire Tegnas Torrent. Most of the steep tributaries were affected by debris flows (6 tributaries), but also debris floods were recognized at 3 steep channels. The morphometric approaches had a satisfactory performance in predicting the two end-member flows, but often failed in recognizing sub-reaches affected by debris floods.</p><p>The comparison between the occurred high-magnitude flows, and the ordinary flows allowed us to infer the existence of relationships between the transport mechanisms, the hydraulic forcing, and channel dynamics. The upheaval of the ordinary flow types did not occur along the entire stream network. The transition from water flows to debris floods occurred for unit stream powers exceeding the threshold of 5000-6000 Wm<sup>-2</sup> or downstream of a channel delivering a large amount of sediment mobilized by debris flow to the receiving stream. The occurrence of debris floods, causing higher channel widening than water flows, appears to be facilitated by the injection of fine material into the flow, which can occur as consequence of channel-bank erosion and overbank floodwater re-entering the channel. Finally, morphometric approaches turned out to be adequate to provide a first-order discrimination of expectable high-magnitude flow types. However, the complex relationships found between flow types and a range of hydraulic, morphological, and geological controlling factors, reveal that a more detailed characterization is necessary for understanding the transport mechanisms and predicting geomorphic hazard that can affect specific channel sites during high-magnitude to extreme hydrological events.</p>

Uniform Water Flows within Rectangular Open Channels of Composite Roughness

2012 ◽  
Vol 2 (2) ◽  
pp. 137-139
Author(s):  
Demetriou J Demetriou J ◽  
◽  
Retsinis E Retsinis E
Keyword(s):  
Open Channels ◽  
Water Flows

Estimation of the virtual water trade between two Spanish regions: Castilla-la Mancha and Murcia

2010 ◽  
Vol 10 (5) ◽  
pp. 831-840 ◽  
Author(s):  
Ángel De Miguel ◽  
Eloy García ◽  
Irene De Buestamante
Keyword(s):  
Water Flow ◽  
Food Processing ◽  
Virtual Water ◽  
Water Transfer ◽  
Water Efficiency ◽  
International Context ◽  
Water Flows ◽  
Spanish Regions ◽  
La Mancha ◽  
Virtual Water Flow

Virtual water is defined as the water needed to produce a product. We can use virtual water flow calculations to estimate the water efficiency of a country, as well as its economic dependence on water resources. Former studies on this area have focused on quantifying the virtual water flows between countries, in an international context. In this study we reduce the action framework to regions within a country, determining the virtual water balance between two Spanish regions: Castilla-La Mancha and Murcia. In 2004, Castilla-La Mancha exported to Murcia 2,453,442 tons of commercial products, from which 1,191,628 tons were agricultural goods. In terms of virtual water, it means 1,365 hm3, including food-processing, and industrial products. It is necessary to add 350 hm3 to the result, because of the water transfer (Tajo-Segura transfer) between the rivers basins of these regions, so the final virtual water number, in 2004, was 1,715 hm3. The other way round, Murcia exported in 2004 2,069,000 tons of products, from which 490,351 tons were agricultural goods. That supposes 712 hm3 of virtual water. Virtual water flow is unbalanced and displaced towards Murcia with a difference of 1,003 hm3.

scholarly journals Erosion Transportation Processes as Influenced by Gully Land Consolidation Projects in Highly Managed Small Watersheds in the Loess Hilly–Gully Region, China

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1540
Author(s):  
Qianqian Ji ◽  
Zhe Gao ◽  
Xingyao Li ◽  
Jian’en Gao ◽  
Gen’guang Zhang ◽  
...  
Keyword(s):  
Similarity Theory ◽  
Design Method ◽  
Simulation Method ◽  
Practical Significance ◽  
Land Consolidation ◽  
Small Watershed ◽  
Flood Peak ◽  
Erosion Area ◽  
The Impact ◽  
Erosion Environment

The Loess Hilly–Gully region (LHGR) is the most serious soil erosion area in the world. For the small watershed with high management in this area, the scientific problem that has been paid attention to in recent years is the impact of the land consolidation project on the erosion environment in the gully region. In this study, the 3D simulation method of vegetation, eroded sediment and pollutant transport was innovated based on the principles of erosion sediment dynamics and similarity theory, and the impacts of GLCP were analyzed on the erosion environment at different scales. The verification results show that the design method and the scale conversion relationship (geometric scale: λl = 100) were reasonable and could simulate the transport process on the complex underlying surface of a small watershed. Compared with untreated watersheds, a significant change was the current flood peak lagging behind the sediment peak. There were two important critical values of GLCP impact on the erosion environment. The erosion transport in HMSW had no change when the proportion was less than 0.85%, and increased obviously when it was greater than 3.3%. The above results have important theoretical and practical significance for watershed simulation and land-use management in HMSW.

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