Analysis of extreme flow uncertainty impact on size of flood hazard zones for the Wronki gauge station in the Warta river

Abstract

In this paper, the impact of maximum flow uncertainty on flood hazard zone is analyzed. Two factors are taken into account: (1) the method for determination of maximum flows and (2) the limited length of the data series available for calculations. The importance of this problem is a consequence of the implementation of the EU Flood Directive in all EU member states. The factors mentioned seem to be among the most important elements responsible for potential uncertainty and inaccuracy of the developed flood hazard maps. Two methods are analyzed, namely the quantiles method and the maximum likelihood method. The maximum flows are estimated for the Wronki gauge station located in the reach of the Warta river. This simple river system is located in the central part of Poland. The length of the available data is 44 years. Hence, the series of the lengths 40, 30 and 20 years are tested and compared with reference calculations for 44 years. The hydrodynamic model HEC-RAS is used to calculate water surface profiles in steady state flow. The Python scripting language is applied for automation of HEC-RAS calculations and processing of final results in the form of inundation maps. The number of trials for each factor is not huge to keep the presented methodology useful in practice. The chosen measure of uncertainty is the range of variability for maximum flow values as well as inundation areas. The estimated values stressed the great importance of the factors analyzed for the uncertainty of the maximum flows as well as inundation areas. The impact of the data series length on the maximum flows is straightforward; a shorter data series gives a wider range of variability. However, the dependencies between other factors are more complex. Hence, the application of methodology based on the simulation and GIS data processing for assessment of this problem seems to be quite a good approach.

Analysis of Spatial Variability of River Bottom Sediment Pollution with Heavy Metals and Assessment of Potential Ecological Hazard for the Warta River, Poland

“…The possibility of using water resources is closely related to a number of factors modified by the type of natural or anthropogenic sources and climate changes. These factors include the quality of water [1][2][3][4][5], the quality of bottom sediments [6][7][8], processes of eutrophication and overgrowth [9,10], hydrological processes, and extreme natural phenomena [11,12].…”

Modelling of climate change impact on flow conditions in the lowland anastomosing river

“…HEC-RAS is a well-known hydrodynamic model for one and two-dimensional hydraulic calculations and is often used in calculating both steady and unsteady, gradually varied flow (Dysarz et al, 2019;Horritt & Bates, 2002). In addition, the HEC-RAS system solves movable boundary sediment transport computations and water quality analysis.…”

Development of methodology for assessment of long‐term morphodynamic impact on flood hazard

“…However, the development of modern measurement techniques such as GPS, LIDAR, satellite imaginary (e.g., Arseni, Roșu, Bocăneală, Constantin, & Georgescu, 2017; Gilles, Young, Schroeder, Piotrowski, & Chang, 2012; Jung, Kim, Kim, Kim, & Lee, 2014; Laks, Sojka, Walczak, & Wróżyński, 2017; Sampson et al, 2012; Sojka, Murat‐Błażejewska, & Wróżynski, 2012; Sojka & Wróżynski, 2013; Walczak, Sojka, & Laks, 2013) as well as modelling technologies, 1D/2D hybrid modelling, parallel processing, etc. (e.g., Brunner, 2016a; DHI, 2017; Dysarz, Wicher‐Dysarz, Sojka, & Jaskuła, 2019; Gąsiorowski, 2013; Kolerski, 2018; Szydłowski, Szpakowski, & Zima, 2013; Yin et al, 2018) has significantly reduced inaccuracies and uncertainties in these areas. In the more predictive analyses, one more factor is important, namely, the lack of knowledge about future inflows to river systems.…”