Establishment of the Sediment Monitoring System for the Sava River Basin

Marina Babić Mladenović1, Damir Bekić2, Samo Grošelj3, Matjaž Mikoš4, Tarik Kupusović5, Dijana Oskoruš6

 

1 Jaroslav Černi Institute for the Development of Water Resources, Jaroslava Černog 80, 11226 Pinosava, Belgrade, Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 University of Zagreb, Faculty of Civil Engineering, Fra Andrije Kačića-Miošića 26, 10000 Zagreb, Croatia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

3 International Sava River Basin Commission, Branimir Centar, Kneza Branimira 29/II, 10000 Zagreb, Croatia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

4 University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova cesta 2, p.p. 3422, 1001 Ljubljana, Slovenia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

5 Hydro-Engineering Institute of Civil Engineering Faculty, Stjepana Tomića 1, 71000 Sarajevo, Bosnia and Herzegovina; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

6 Meteorological and Hydrological Service of the Republic of Croatia (Zagreb-HR), Gric 3, 10000 Zagreb, Croatia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

 

Abstract

The Sava River Basin (further SRB), a major sub-basin of the Danube River in South-East Europe, is shared by five countries, and hosts a population of roughly 8.5 million. Slovenia, Croatia, Bosnia and Herzegovina, and Serbia are Parties of the Framework Agreement on the Sava River Basin (FASRB). Its implementation body is the International Sava River Basin Commission (ISRBC) which is responsible for development of joint plans and programs regarding the sustainable water management among others. ISRBC has developed the Protocol on Sediment Management to the FASRB which affirms the need for efficient cooperation among the Parties and for promotion of sustainable sediment management (SSM) solutions. On the Ministerial meeting held on July 6th 2015 in Brčko the Parties to the FASRB signed the Protocol on Sediment Management to the FASRB which affirms the need for efficient cooperation among the Parties and for promotion of sustainable sediment management (SSM) solutions. The BALSES project (2014) was a step towards the understanding of sediment balance in SRB. Although it revealed that in the moment direct water-sediment interrelationships within SRB cannot be determined, it opened a door for future – hopefully when many present problems (as insufficient number of monitoring sites, very limited data and differences in measurement methodology) will not be the obstacle. However, the analysis and interpretation of the existing sediment database enabled the understanding of some basic characteristics of the sediment transport in the Sava River, where suspended sediment has the most important role. The anthropogenic factors (existing dams and reservoirs, river training structures and excavation of sediment) were also recognized as important. Within the framework of a cooperative effort associating the UNESCO Venice Office (UVO), ISRBC, the European Sediment Network (SedNet) and the UNESCO-IHP International sediment Initiative (ISI) ISRBC established the Core expert group for the implementation of the project "Proposal of the Establishment of the Sediment Monitoring System for the Sava River Basin". This paper presents the main results of this project.

Keywords: Sava, sediment, environment, monitoring, management.

 

 

Sediment Transport Processes in Rivers

Sediment transport is the general term used for the transport of material (clay, silt, sand, gravels, and boulders) in rivers and streams. The transported material is called sediment load. Distinction is made between bed load and suspended load. The bed load characterizes grains rolling, sliding and saltating along the river bed while suspended load refers to smaller sediment grains maintained in suspension by turbulence.

The total sediment discharge in a stream is the total volume of sediment particles in motion per unit time. It includes the sediment transport by bed load motion and by suspension as well as the wash load (Chanson and James, 1998).

Sediment transport is a natural process of transporting solid particles from erosion sources to deposition or sedimentation areas (Mikos, 2005). The important source of sediments is soil erosion. Geological soil erosion occurs as surface removal of farm, forest and other erodible soils in the form of sheet erosion, inter-rill and rill erosion, gully erosion or deflation, mainly caused by impacts of raindrops (splash erosion, rain erosion) and overland flow on bare soils or land without dense vegetation cover to protect soils. Accelerated erosion is the speeding up of erosive processes, either directly or indirectly, by the intervention of man, such as deforestation, overgrazing, construction sites etc.

Other important sediment sources are deposits of mass wasting phenomena, driven by gravity (rock falls, rock slides, landslides, debris flows, mud flows) exposed to fluvial processes of erosion, transportation and sedimentation. Subjects of these processes are fluvial sediments - solid particles and particles of rock material that have been transported from their sources and deposited elsewhere by flowing water.

Sediments in rivers can also occur from morphological changes of river channel in vertical and lateral direction (river bed and bank erosion) on the upstream river sections. These are natural morphological changes that can be exacerbated by the man intervention.

Sediment transport in rivers and streams involves two-phase flow of a water-sediment mixture. The most important physical properties of a water-sediment mixture are specific weight of a mixture (the total weight of solid and water in the voids per unit total volume), specific mass of a mixture (the total mass of solid and water in the voids per unit total volume), volumetric sediment concentration (the volume of solids over the total volume), as well as dynamic and kinematic viscosity of a mixture.