Preliminary Results of Hydrologic Reconstruction of the May 2014 Kolubara River Flood

Stevan Prohaska1, Nikola Zlatanović1

 

1 Institute for the Development of Water Resources "Jaroslav Černi", Jaroslava Černog 80, Belgrade, Serbia

 

Abstract

The disastrous flood that affected the Kolubara River basin in May 2014 caused significant damage of existing embankments, flooding of open mine pits, agricultural land, towns and villages, which resulted in the loss of human lives and material damage, on a scale never before seen in the region. The authors of this paper have developed a hydrological model whose task was to simulate the flood and determine the spatial and temporal distribution of the flood throughout the basin. The software package HEC-HMS (Hydrologic Engineering Center – Hydrologic Modeling System) was used to develop the hydrological model. The Kolubara River basin was divided into multiple sub-basins, with one official hydrological station at the basin outlet. The outlets of upstream sub-basins represent input profiles for the model component to calculate flood wave propagation along the Kolubara River and its major tributaries. The existing hydrological stations along these streams represent control profiles, while the output profile from the model is defined by the position of the hydrological station Draževac on the Kolubara River. The developed hydrologic model of the Kolubara River basin is a parametric semi-distributed rainfall-runoff model that consists of a finite number of sub-basins, each considered as a separate unit. The division into sub-basins was based on physical and hydrographic characteristics (for tributaries), and on characteristic profiles (hydrological stations, reservoirs, etc.). For each sub-basin, the following basic components were included: an effective rainfall model, a direct runoff transformation model and a baseflow model, while the links between basins were calculated using a model of flood wave propagation along the river reaches. The model of flood wave transformation was applied for reservoirs and retention basins (e.g. Stubo-Rovni reservoir on the Jablanica River, retention basin Paljuvi-Viš on the Kladnica River, open-pit coal mines, etc.). Provided in this paper are appropriate numerical and graphical indicators of characteristic hydrographs in the Kolubara River basin during the flood of May 2014.

 

 

Introduction

 

In mid-May 2014, the entire Kolubara River basin was affected by heavy rainfall. Extreme runoff from hill slopes led to the coincidence of flood waters from both left and right tributaries of the Kolubara River, which flowed simultaneously into the Kolubara River. These tributaries all have a very torrential character, with rapid onset of the flood wave (Petković and Stefanović, 2015). At river reaches with flood protection facilities (mainly settlements in the downstream part of the basin), embankments overflowed at several locations in a relatively short period of 1-2 days. The city of Obrenovac suffered the most consequences as a result. Flood waters simultaneously overflowed the main river channels of the Kolubara, Peštan and Vraničina rivers in the vicinity of the Kolubara lignite coal mine, completely flooding the open-pit mines "Tamnava-Zapadno polje" and "Veliki Crljeni". The breach occurred upstream of the southern edge of the "Tamnava-Zapadno polje" mine when the embankments of the Kolubara River and its tributaries Vraničina and Peštan were overtopped. As a result, almost the entire flow of the Kolubara River was completely redirected upstream through the channel of the Vraničina River and the Skobalj Stream, from the Vraničina mouth towards the "Tamnava - West Field" mine.

The "Tamnava-Zapadno polje" mine was also flooded by the Kladnica River from the west, when the Kladnica dam was overflowed.

Significant damage also occurred to some official monitoring stations of the Republic Hydrometeorological Service of Serbia (RHMSS) during the flood in May 2014. At some stations, the water level measuring equipment was completely flooded, some even completely destroyed. Other stations suffered upstream embankment breaches that significantly altered flow paths, and as a result the entire river discharge could not be gauged during the flood peak. Another issue that occurred on some equipment was jamming of the limnigraph needle, resulting in recorded hydrographs appearing "cut off" and the flood peak being unrecorded.

With this in mind, the need arose to hydrologically model the flood of May 2014 on the Kolubara River and its tributaries. The authors of this paper developed a hydrological model to determine the origin, formation and propagation of the flood throughout the basin. The HEC-HMS (Hydrologic Engineering Center – Hydrologic Modeling System) software package was used to develop the hydrologic model, and the preliminary results are shown in this paper.