th
Abstract: As a consequence of undeveloped waste management system in the past, Serbia at the moment has more than 3400 wild dumps, around 150 municipal non sanitary landfills and less than 10 sanitary landfills.
Beside sanitary landfills, which mostly fulfill regulation requirements, selection of location for all other landfills were based predominantly on distance from the setlements without taking into account other aspects.
Landfills located in potential flood zones and zones with higher level of groundwater represent a threat to surrounding areas and surface/groundwater bodies due to waste emissions and subsequent pollution, especially when landfill bodies are not designed properly, which is often case in countries with undeveloped waste management system. During the floods in May 2014 many Municipalities in Serbia suffered significant damage in the field of waste management. The main goal of this paper was to establish new risk assessment aproach for determing flood risk of landfills based on hydrological aspects, which will help to establish the registar of the most threatened landfills in Serbia.
Key Words: Flood / Landfill /Risk assessment
/Groundwater
1. INTRODUCTION
During the third week of May, record-breaking amounts of rainfall were recorded. More than 200 mm of rain fell in western Serbia which is the equivalent of 3 months of rain under normal conditions. The heavy rainfalls led to soil saturation and a rapid and substantial increase of water levels in the main rivers in western, south-western, central and eastern Serbia. Increase of water level caused significant rise of groundwater level.
Overall the floods affected some 1.6 million people living in 38 municipalities, mostly located in central and western Serbia. Total value of damage and losses is estimated to the amount of EUR 1.7 to 1.8 billion [1].
Waste management practice in Serbia currently comprises of waste collection and disposal, mostly on non-sanitary landfills without treatments or control prior to disposal. In last few years there is tendency of separating some of the recyclable waste such as PET, paper, cardboard and metal. Even though some waste fractions are preselected for recycling, all other waste, including organic waste ends up on landfills which do not fulfill basic requirements for safe disposal. As a consequence of undeveloped waste management system in the past, Serbia at the moment has more than 3400 wild dumps, around 150 municipal non sanitary landfills and less than 10 sanitary landfills [2].
Due to uncontrolled waste disposal, those non sanitary landfills have been identified as one of the major threats and sources of contamination of environment in
Serbia.
Landfills located in potential flood zones and zones with higher level of groundwater represent a threat to surrounding areas and surface/groundwater bodies due to waste emissions and subsequent pollution, especially when landfill bodies are not designed properly, which is often case in countries with undeveloped waste management system. The risk and its consequent emissions of chemicals or hazardous waste is higher in countries with economy in transition such as Serbia where risk mitigation measures have not been systematically implemented yet [3].
Due to potential negative influence of solid waste deposition sites, location of landfills in areas that do not have appropriate soil types (compacted clay with low hydraulic conductivity) or are in 100-year flood plains, and those that specify smallest acceptable distances between landfills and populated areas need to be avoided
[4]. Even though National regulations and international standards require minimum distance of 500 m from any surface water [5,6], many landfills in Serbia are placed closer to the river banks [2].
Landfill leachates, are significant sources of groundwater pollution and pose major risks to groundwater quality [7].
Research on quality of groundwater in the vicinity of the landfill in Serbia shows high values of COD, BOD5 and permanganate index, which indicate the high organic pollution of this water. Also high level of potassium, calcium and magnesium, in both, rainy and dry season, are recorded [8] .
During a flood event it has to be assumed that the landfill body becomes water saturated and that this leads to a substantial mobilisation of pollutants, since the presence of water enhances decomposition and transport processes [9-12].
Flooding of landfills not only helps propagation of pollution but also endangers landfill structure

characteristics or stability. At several landfills which are located in flooded municipalities structural integrity was compromised by water that carried away 10 to 30 % of landfilled waste.
At various locations, landfilled waste was eroded by the flood, was transported downstream and then deposited. Heavy metal and organic pollutant contamination of soils is one of the major environmental problems resulting from the regular flooding of rivers in
Europe [13].
There are studies regarding landfills in Serbia which are based entirely on landfill distance from river bed and which primarily refer to prioritization regarding flood risk [3], as well as general environmental risk assessment based on larger number of parameters [2] but studies based on detailed analysis from hydrological aspects are not realized by now.
2. METHODS
24 municipalities of 38 that were affected by floods sustained greater damage in the domain of solid waste management among other. In some municipalities landfills were partially or completely flooded which resulted in significant spreading of pollutants from these, mostly unregulated landfills. However there is a question of what were the consequences of adverse hydrological situation for other landfills in flood affected areas.
There is considerable number of wild dumps in considered municipalities (6 to 65 open dumps per selected municipality), beside main non sanitary solid waste landfills. These wild dump sites have extremely low amounts of deposited waste and for that reason they are not the subject of this research.
Risk assessment for municipal solid waste landfills in specified municipalities was realized taking in consideration four aspects: distance between landfill and surrounding water bodies, groundwater risk assessment, saturation of soil with water at landfill location and determination if landfill was actually flooded during the flood period in May 2014.
Two aspects of this risk assessment are directly related to flood disaster that occurred in May 2014.
„Flooded landfill“ and „Compromised with water saturated soil“. On the other hand other two risk assessment aspects „distance from the water bodies “
(river basins, lakes, etc.) and „state (level) of groundwater at location of the landfill“ are not as directly related to flood disaster as two preceding aspects because groundwater levels and soil saturation can change without disaster occurrence and can be analyzed independently.
Table 1. Municipality landfills flood risk assessment
Municipality
Bajina Bašta
Čačak
Jagodina
Status
A – Flooded landfill
B – Compromised with water saturated soil
C – Influence on groundwater
D – Less than 500 m form the water body
A, D *
C, D *
C, D
Municipality
Koceljeva
Kosjerić
Kragujevac
Kraljevo
Krupanj
Lazarevac
Loznica
Ljubovija
Mali Zvornik
Status
A – Flooded landfill
B – Compromised with water saturated soil
C – Influence on groundwater
D – Less than 500 m form the water body
C,D *
C, D *
C, D *
C, D *
-
-
B, C, D *
A, C, D *
A, C, D *
Obrenovac
Osečina
Paraćin
Smederevska palanka
Svilajnac
Šabac
Šid
Trstenik
A, C, D
A, D
B, C,D
B
B, C
B, C, D *
Ub
Valjevo
Varvarin
Velika Plana
B
-
A, C, D
B, C, D *
A, C, D
B, C, D
*- Less than 100 m from the water body
Previous research regarding landfills in Serbia included recording of landfill’s GPS coordinates and other attributes such as landfill surface or area, waste volume, waste depth etc. GPS coordinates were used for positioning of landfills in satellite imagery (SPOT6,
Pleiades, Rapid Eye, TerraSar X, Copernicus and
Dartmouth).
Data on landfill location from previous research was used for determination of distance to water bodies [13].
Positioning was done through exporting of landfill GPS coordinates, overlapping the coordinates with map of the river beds in Serbia and manual measuring the distance of each landfill to the nearest water body.
Determination of second risk assessment aspect was conducted by positioning landfills on the map of groundwater vulnerability in Serbia which was made for purposes of project “Monitoring of groundwater resources in Serbia” [15].
This map displays six degrees of groundwater according vulnerability which ranges from very low to very high risk of vulnerability. Degree of vulnerability was determined through analysis of following aspects:
Influence of terrain slope on infiltration, influence of soil type and type of vegetative cover on vulnerability of groundwater, thickness of overlaying layer, geological i.e. hydrological characteristics of terrain and depth to groundwater level.
Determination of flooded landfills and soil saturation with water at landfill locations was conducted through export of landfill GPS coordinates and their overlapping with satellite imagery with indicated layers of flooded surfaces, and soil surfaces saturated with water. Satellite

imagery used (SPOT6, Pleiades, Rapid Eye, TerraSar X,
Copernicus and Dartmouth) was obtained at online service of Republic of Serbia Geodetic authority.
3. RESULTS AND DISCUSSION
Based on the results shown in table above, one can see that 18 out of 24 landfills are located less than 500 m from rivers although it is the minimum required safe distance. Moreover, 11 landfills are located on a distance less than 100 m from the river basins. Seventeen out of
24 landfills are placed on locations with high average groundwater levels wherein fluctuations in groundwater levels can reach deposited waste and increase dispersion of pollutants. It was determined that during the flood wave in May 2014 seven landfills were partially or completely flooded and 8 more were in the zones with water saturated soil.
All flooded landfills are located less than 500 m from water bodies. Three of the flooded landfills are located on a location which is less than 100 m and 4 of flooded landfills are located between 100 and 300 m from water bodies.
At landfills which belong to risk group from aspect of flood probability, water saturated soil and high levels of groundwater some measures as provision of alternative location for landfilling, closure and remediation of old location need to be taken in order to prevent future spreading of pollution. The method of remediation must adequately isolate landfill body which means that in combination with final top cover and bottom liner must provide sufficient level of protection in the case of high probability of high groundwater levels and water saturated soil occurrences. Placing top cover and bottom liner is technologically and financially more complex.
Other direct measures can involve building of embankments to direct potential flood waves.
4. CONCLUSION
Looking at the results in the area of factors not directly related to disaster it can be concluded that chosen landfill locations pose high risk in the area of aquatic pollutant dispersion. Although there is law that prohibits placing landfills at such unfavorable locations, activities on remediation of several decades old landfills that are currently in use are rare. In order to improve the environment state it is necessary to be innovative and to apply existing legislation more strictly, especially in the area of prevention. Experience gained during analysis of flood consequences must result in measures that will increase flood resilience of municipal solid waste landfills.
Results obtained by this research in selected municipalities are causing for concern and it is necessary to carry out the same analysis for all landfills in Republic of Serbia and to establish the register of threatened landfills, potentially with quantification of the risk.
Fig. 1. Obrenovac landfill with flooded and water saturated soil layers.
The estimate of landfill vulnerability degree was based on combined usage of satellite imagery and known terrain characteristics determined during the site visits.
The following picture shows an example of landfill marked on satellite image of the Obrenovac area where landfill surface is marked by white polygon , flooded surfaces by smaller print pattern and soil saturated with water is marked by larger print pattern.
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