Vistula River bed erosion processes and their influence on Warsaw’s flood safety

Abstract

Large cities have historically been well protected against floods as a function of their importance to society. In Warsaw, Poland, located on a narrow passage of the Vistula River valley, urban flood disasters were not unusual. Beginning at the end of the 19th century, the construction of river embankment and training works caused the narrowing of the flood passage path in the downtown reach of the river. The process of bed erosion lowered the elevation of the river bed by 205 cm over the 20th century, and the consequences of bed lowering are reflected by the rating curve change. Conditions of the flood passage have been analysed by the CCHE2D hydrodynamic model both in retro-modelling and scenario simulation modelling. The high water mark of the 1844 flood and iterative calculations in retro-modelling made possible estimation of the discharge, Q = 8250 m 3 s -1 . This highest observed historical flood in a natural river has been compared to recent conditions of the Vistula River in Warsaw by scenario modelling. The result shows dramatic changes in water surface elevation, velocities, and shear stress. The vertical velocity in the proximity of Port Praski gauge at km 513 can reach 3.5 m s -1 , a very high value for a lowland river. The average flow conveyance is improving due to channel erosion but also declining in the case of extreme floods due to high resistance from vegetation on the flood plains.

Stormwater Management in the City of Warsaw: A Review and Evaluation of Technical Solutions and Strategies to Improve the Capacity of the Combined Sewer System

“…The water is kept in check by dikes, which, in Warsaw, are prepared for a thousandyear water, i.e., with a flow Q p0.1% = 9960 m 3 s −1 [16]. However, there is always some uncertainty about their durability.…”

The application of two‐dimensional hydrodynamic models for underwater archaeological finds from the Vistula River in Warsaw, Poland

“…The highest instrumentally measured discharge in Warsaw has been recorded during the flood of 2010 and equalled 5,899 m 3 s −1 . An estimation of the highest historical flood level from 1844 is 8,250 m 3 s −1 (Kuźniar & Magnuszewski, ; Magnuszewski & Moran, ).…”

“…The lowering of the river's bed continued and can be demon- (Fal & Dąbrowski, 2001) During An estimation of the highest historical flood level from 1844 is 8,250 m 3 s −1 (Kuźniar & Magnuszewski, 2010;Magnuszewski & Moran, 2014).…”

“…It is obvious that the August 2015 drought established the lowest value for water levels but not for discharge.The natural narrowing created by the river's terraces was further intensified by the construction of dikes built at the end of the 19th century and during the first half of the 20th century. Spacing of the dikes outside the borders of Warsaw fluctuates from 1,000 to 1,500 m whereas in the downtown section, between the 511th and 514th km, ranges from 470 to 480 m(Magnuszewski & Moran, 2014). What is more, to gain control both during the average and the low flows first river training works were completed at the end of the 19th century and were aimed at directing water to the water intake structure of Warsaw's water supply system.…”

Bathymetric Monitoring of Alluvial River Bottom Changes for Purposes of Stability of Water Power Plant Structure with a New Methodology for River Bottom Hazard Mapping (Wloclawek, Poland)

“…Erosion processes in the river alluvial geological environment have been studied by [ 3 , 24 , 25 , 26 , 27 ]. It is evident that the formation of potholes is one of the basic hazards for water power plant structures.…”