Elena Dupliak 1*, Svitlana Velychko 2*
1,2 Faculty of Engineering system and Ecology of Kyiv National University Construction and Architecture, address: Povitroflotsky Avenue, 31, Kyiv, 03680 Ukraine
Received: 03/10/2018, Accepted: 03/18/2018, Available online: 03/20/2018.
*Corresponding author: e-mail: firstname.lastname@example.org
Under a creative commons license. Volume 2, Issue 1, 2018, pages: 41-47.
Author Keywords: 1% probability flood, backwater curve, hydraulic calculation, confluence of flows.
The following sequence of curve calculation is proposed in the point of confluence of main river and tributaries during flood of 1% probability on the example of Tisza River. The method of calculation was used to determine flood zones during flood of 1% probability and assessment of effectiveness of the proposed active and passive flood protection structures in the Basin of Tisza River.
Tisza River is the largest left-bank tributary of the Danube River. Its length is 967 km, the basin area is 157,000 km2. Flowing through the territory of five countries - Ukraine, Romania, Czech Republic, Hungary and Serbia, the river Tisza rises in Ukraine on the slopes of the Carpathians from two separate rivers - the Black and White Tisza. Tisza receives its name after confluence of them. Basin area of Tisza in Ukraine is 12 760 km2, its length is 220.4 kilometres from the source (the Black Tisza) to the Ukraine-Hungary border (estuary of the Batar river) . Floods are formed in the Tisza river basin at any time, and may be storm, snow or a snow- rain origin.
Floods are characterized by short duration (3-5 days). The magnitude of rise in water levels is often extraordinary in rivers, causing floods, that leading to great damage for population, agriculture and environment .
Simulation of the channel capacity was carried out for flood 1% probability under natural conditions and flood zones were identified . Based on the analysis of flood zones there were developed anti-flood measures of passive nature (construction of dams, bank strengthening, forest planting on the slopes, clearing of the river beds) and active (dry mountain reservoirs, polders) .
The calculations of water levels of 1% probability were carried out for the case of full implementation of flood control measures using software MIKE 11.
Long-term monitoring of flow rates and the levels of water in the Tisza River and its tributaries  have shown that simultaneously flood passing often takes place that leads to forming backwater curve. The increased value of water levels is ranged from 0.2-0.5 m, which significantly affects the height of protective structures in the point of flows confluence.
Today there are no regulations or recommendations for the calculation and design of hydraulic structures in the points of flows confluence. That's why it is necessary to develop an engineering method of backwater curve calculation for practical purposes.
The following sequence of backwater curve calculation at the section of flows confluence of the main river and tributary is represented. This method of calculation is simple, does not require special equipment and can be used for engineering calculations. Testing of calculation methods showed that if the ratio of flow rates of the main river and its tributary is Q3/Q1<0.2, backwater curve is absent (value within the accuracy of calculations). If the ratio is Q3/Q1>0.3 and angle less than 900, the calculation using equations (6) and (5) give almost identical values.
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Please cite as: O. Dupliak, S. Velychko “Simulation of the channel capacity for Tisza river considering backwater curve during flood.” USEFUL online journal, vol. 2, no. 1, pp. 41–47, March 2018. DOI: https://doi.org/10.32557/useful-2-1-2018-0005