Science of the Total Environment 407 (2009) 3674–3680

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Science of the Total Environment j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s c i t o t e n v

Flooding of municipal solid waste landfills — An environmental hazard? David Laner ⁎, Johann Fellner, Paul H. Brunner Vienna University of Technology, Institute for Water Quality, Resources and Waste Management, A-1040 Vienna, Karlsplatz 13/226, Austria

a r t i c l e

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Article history: Received 23 April 2008 Received in revised form 2 March 2009 Accepted 8 March 2009 Available online 5 April 2009 Keywords: Landfill Flooding Municipal solid waste (MSW) Environmental pollution Erosion

a b s t r a c t Municipal solid waste (MSW) landfills pose a long-lasting risk for humans and the environment. While landfill emissions under regular operating conditions are well investigated, landfill behaviour and associated emissions in case of flooding are widely unknown, although damages have been documented. This paper aims at developing a methodology for determining the proportion of MSW landfills endangered by flooding, and at evaluating the impact flooded landfills might have on the environment during a flood event. The risk of flooding of MSW landfills is assessed by using information about flood risk zones. Out of 1064 landfills investigated in Austria, 312 sites or about 30% are located in or next to areas flooded on average once in 200 years. Around 5% of these landfills are equipped with flood protection facilities. Material inventories of 147 landfill sites endangered by flooding are established, and potential emissions during a flood event are estimated by assuming the worst case of complete landfill leaching and erosion. The environmental relevance of emissions during flooding is discussed on the basis of a case study in the western part of Austria. Although environmental hazards need to be assessed on a site- and event-specific basis, the results indicate that flooded MSW landfills represent in general small environmental risks for the period of flooding. The longer term consequences of flooding are discussed in a next paper. © 2009 Elsevier B.V. All rights reserved.

1. Introduction Numerous studies investigating the behaviour of municipal solid waste (MSW) landfills and their emissions were carried out during the last decades. With respect to the legal background of many European countries they mainly focused on the generation of leachates and methane (greenhouse gas and energy recovery from landfills) and the duration of the after care period, which characterises the time until landfill emissions become environmentally compatible. Depending on the waste composition, the climatic conditions and the methodology applied, aftercare periods of 200 to 500 years were estimated (Belevi and Baccini, 1989; Stegmann and Heyer, 1995; Ehrig and Krümpelbeck, 2001). According to these authors, municipal solid waste deposits contain a large, long lasting risk potential for humans and the environment. Whereas the normal operation of landfills and the associated emissions are well investigated, the behaviour of waste deposits in case of flooding is widely unknown. 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 (Klink and Ham, 1982; Bogner and Spokas, 1993; Christensen et al., 1996). Additionally water saturation of landfilled waste may lead to problems of mechanical stability, which could cause shear and sliding fractures (cf. Blight and Fourie, 2005). ⁎ Corresponding author. Tel.: +43 1 58801 22644. E-mail address: [email protected] (D. Laner). 0048-9697/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2009.03.006

In consideration of the long residence time of a landfill even flood events of low probability of occurrence (e.g. 200-year recurrence interval flood) need to be considered, when evaluating the potential risks emanating from landfills. The present paper aims at (1) developing a methodology to determine the proportion of flood prone MSW landfill sites, and (2) assessing the potential release of substances from landfills affected during a flood event in Austria. Based on data about potential inundation areas for Austria, the flood risk exposure of all reported MSW landfills is evaluated. For these sites the potential emissions during a flood are estimated by assuming the worst case, a loss of landfill stability, and calculating substance release based on inventory data. The relevance of subsequent emission loads during a flood event is discussed on a general level and via a case study. Finally, the need for future research with regard to long-term emissions due to flooding, that has not been included in the present investigation, is highlighted.

2. Natural hazards and MSW landfills Exogenic states of emergency during the lifetime of MSW landfills are commonly associated with earthquakes and their impacts on landfill stability. Hence, several authors report earthquake related damages (e.g. Anderson, 1995; Matasovic et al., 1998) and geotechnical analysis of the seismic behaviour of MSW landfills (e.g. Krinitzsky et al., 1997; Thusyanthan et al., 2004). In addition to earthquakes,

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Fig. 1. Reported sites of controlled MSW landfills (squares) and old MSW landfills (triangles) in Austria (basic map: Fürst and Hörhan, 2007).

flooding represents a disaster for landfills, too (cf. Kremen and Lachman, 2001). The erosion of landfilled material and the release of pollutants from flooded landfills are well documented (e.g. Habersack and Moser, 2003; Geller et al., 2004; Young et al., 2004; Vorarlberg, 2005b). For instance, Geller et al. (2004) observed during the 2002 flood of the Elbe River increased flows of pollutants (mainly metals and persistent organic substances) into floodplain soils and river sediments due to inundated landfills. At various locations, landfilled waste was eroded by the flood, was transported downstream and then deposited. Heavy metal and arsenic contamination of the Elbe catchment area were partly attributed to flooded landfills (Rank et al., 2003). Also, Clevers et al. (2004) emphasize that heavy metal and organic pollutant contamination of soils is one of the major environmental problems resulting from the regular flooding of rivers in Europe. Several studies investigating the flooding of tailings or abandoned mining sites, conclude that releases of hazardous substances during flood events are generally a major environmental concern (cf. U.S. Environmental Protection Agency, 1997; Prat et al., 1999; Lin et al., 2007). However, these results are only partly suited for predicting the behaviour of MSW deposits, because MSW contains mainly organic materials such as paper, biomass, and plastics. The processes of transformation and transport are distinctly different, and so are the resulting emissions. For MSW landfills, quantitative assessments of the environmental impacts during and after a flood event are generally missing. Curtis and Whitney (2003) performed a geomorphic and hydrologic assessment of hazardous substances from a MSW landfill in the Canadian River floodplain. They analysed erosion potentials and substance release risks depending on specific discharge events. Their analysis indicates that the total energy expenditure of a discharge event is the most important factor when estimating the erosion potential of a flood. However, although they state that the potential release of hazardous substances via flooding is of concern, they did not estimate potential emission levels in case of landfill erosion. Accidents involving MSW landfills are often due to mechanical instability. Blight and Fourie (2005) provide a review of catastrophic failures of waste landfills, highlighting the impact of such disasters on both the environment and the population. One of the first documented failures of a MSW landfill took place in 1977 in Sarajevo (Gandolla et al., 1979), luckily without casualties. 18 years later at the Umraniye– Hekimbasi refuse dump in Istanbul a massive land-fill slide occurred destroying several houses and killing 39 people (Kocasoy and Curi, 1995). More recently, in an incident at the Payatas dumpsite in Manila 330 scavengers have been buried as a result of a landfill collapse, and in 2005 a landfill slide took place at the Indonesian Leuwigajah dumpsite after heavy rainfall, killing 147 people who lived in a valley nearby the landfill (Agamuthu, 2006). Since systematic reviews of

MSW landfill failures are lacking, this list remains punctual and incomplete. 3. Materials and methods In this section, the procedures are presented for developing a methodology to determine (1) flood prone MSW landfill sites , and (2) the potential release of landfill pollutants via flooding. As a case study area, Austria was chosen because of data availability: information about MSW landfill sites in Austria is provided by the Austrian Federal Waste Management Plan (Krammer et al., 1992; Lebensministerium, 2006a), by various waste management reports published by federal and local authorities (Lunzer et al., 1998; Kärnten, 2000; Flögl, 2002; Tirol, 2002; Rolland and Oliva, 2004; Burgenland, 2005; Niederösterreich, 2005; Vorarlberg, 2005a), and by close collaboration with the Austrian Federal Environment Agency (AFEA). The latter maintains a database about old MSW landfills which were mainly operated before 1989 (cf. Skala et al., 2007). The distinction between “old” MSW landfills and “controlled” MSW landfills (deposition took place after 1989) corresponds to the legal framework for financing brownfield remediation in Austria (ALSAG, 1989). However, as these two categories of MSW landfills differ with respect to deposition characteristics (e.g. age, waste composition, size, profile) and technical standards (e.g. liner systems, gas and leachate treatment, flood protection facilities), they are also discussed separately in this paper (cf. Kjeldsen and Christophersen, 2001). The list of controlled landfills in Austria comprises 103 MSW landfills. The list of 961 old MSW landfills is based on enquiries in the AFEA database of old landfills with an overall volume of more than 25,000 m3. Although the compilation of MSW landfills (see Fig. 1), both controlled and old, is clearly not comprehensive (e.g. the degree of detection for old MSW landfills in the AFEA database is supposed to be less than 70% (Skala et al., 2007)), it represents an unbiased sample for evaluating the risk of flooding for Austrian MSW landfills. The evaluation of the flood risk exposure of MSW landfills is based on data about flood risk zones in Austria (HORA) provided by the Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW) (Lebensministerium, 2006b). This dataset provides information about potential flood inundation zones along rivers for discharges with a return period of T = 30 years, T = 100 years, and T = 200 years. The discharges of the T-year flood were estimated using various sources of information including flood peak samples, rain-fall data, runoff coefficients and historical flood data (Merz et al., 2008). The temporal, spatial and causal information expansion by combining hydrological information as available allowed for a nation wide approach, based on uniform assumptions and information, with a large amount of information on the local hydrology. Finally, the estimated flood discharges were transformed to

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Table 1 Evaluation categories for the flood risk exposure of MSW landfills based on the HORA data about flood risk zones in Austria.

Table 2 Average characteristics of controlled MSW landfills potentially endangered by flooding and old MSW landfills endangered by flooding (Median values and standard deviations).

Criteria (based on the HORA data about Austrian flood risk zones) Landfill is situated within a flood risk zone with a recurrence interval of 200 years or less. Probably Distance between landfill and a flood risk zone with a recurrence endangered interval of 200 years is less than 150 m. Probably not No designated flood risk zone within a distance of 150 m to the landfill. endangered

Average site

Risk category Endangered

the flood risk zones via hydraulic modelling. As this delineation of flood risk zones within HORA disregards technical flood protection measures, it is an indicator for the potential risk of flooding. Public access to the flood risk mapping is provided via an Internet platform: http://www.hochwasserrisiko.at. Within this study the potential risk of flooding a landfill is divided into three categories: “probably not endangered”, “probably endangered”, and “endangered” (see Table 1). The latter two make up the number of potentially endangered landfill sites in Austria. The categories in Table 1 were established within this study and are based on the location of the landfill site (defined by point coordinates) and the distance from a potential flood risk zone indicated in HORA. These criteria can be queried for all landfill sites using a geographical information system (GIS). However, individual landfill geometries cannot be taken into consideration by this procedure (see Fig. 2). In reality the landfill geometry is generally not circular and site coordinates are not located necessarily in the centre of the landfill body. Hence, in order to verify the assumed distance of 150 m for evaluating whether a site is potentially endangered by flooding or not, a visual assessment of the flood risk at each site was conducted for all the 103 controlled MSW landfill sites. Using an online GIS displaying the HORA flood risk zones (Lebensministerium, 2006b), aerial photographs of the individual landfill sites were scanned with respect to their neighbourhood to

Sample size Average deposition height [m] Mean residence time of MSW [yrs] Infiltration ratec [mm yr− 1 m− 2] Volume [m3] Area [m2] a b c

Controlled landfill

Old landfill

Median v.

Std. dev.

Median v.

Std. dev.

34a 12 18 540 430,000 22.600

– 7 8 420 830,000 74,000

113b 4 35 290 78,000 22,000

– 5 12 350 253,000 44.600

Number of potentially endangered controlled MSW landfills. Number of endangered old MSW landfills. Calculated from the regional water balance at the landfill site (P-ETact = I).

potential inundation zones. It was found that all the landfills which were classified as “endangered” are at least partly located in the flood zone corresponding to a river discharge with a recurrence interval of 30 years. Landfills in the category “probably endangered” were partly inundated or directly bordering to a designated flood zone in HORA. Only two of the landfills designated as “probably not endangered” were found to be directly next to potentially inundated areas. Thus, the assumption of a circular landfill surface with a radius of 150 m represents a feasible approximation of the real landfill topology. Nevertheless, the classification in Table 1 should be considered as a coarse identification of potentially endangered MSW landfills. Hence, for an individual, site-specific analysis of the flood risk exposure, the individual geometry of the landfill body and the existence of technical flood protection measures have to be taken into account. The emission potential and the substance release during a flood event are estimated for potentially endangered, controlled MSW landfills and endangered old MSW landfills. The restriction of the further investigations in case of old landfills to “only” endangered sites is due to their large number. The scenario to estimate the potential substance release during a flood event considers the loss of stability of the waste body due to

Fig. 2. Schematic illustration of the procedure to evaluate the potential risk of flooding for a MSW landfill based on the HORA dataset.

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Fig. 3. Evaluation of the flood risk exposure of Austrian MSW landfills (top: number of landfills, bottom: volume of landfilled MSW).

erosion. The available pollution potential of single substances was assessed according to investigations of Baccini et al. (1987) and Döberl et al. (2002), who determined transfer coefficients for Corg, N, P, Cl, Fe, Pb, Cu, Zn, and Cd in dependence of landfill age. Their results show that after 25 years of landfilling (which represents the average age of the considered landfill sites, cf. Table 2) the initial substance load of the disposed waste remains almost unaltered. Based on their investigations it was assumed that in case of landfill erosion the substance load discharged amounts to 80% for Carbon, to 90% for nitrogen and chloride, to 95% for Phosphor, and to 99% for heavy metals, of the initial content of the landfilled MSW. Sm;i = mwaste
ci
Ri Sm,i mwaste ci Ri

ð1Þ

Discharged load of substance i [kg] Waste mass landfilled [kg] Initial content of substance i of the waste landfilled [kg/kg] Remaining fraction of substance in the landfill referred to its initial content at the time of disposal [−], e.g. for Corg = 80%

These emissions comprise the whole substance inventory in the landfill at the time of flooding and subsequent erosion. Hence, the released pollutants are to a large portion still contained in the landfilled waste goods (e.g. plastic bags, tins, paper…). The potentially soluble content of substances in the waste set free via flooding is estimated using data of Belevi and Baccini (1989), who performed leaching

experiments on waste samples taken from MSW landfill sites at the end of the intensive reactor phase. The use of potentially extractable substance fractions determined by shaking leaching tests is considered appropriate due to the intensive water contact of the eroded waste and negligible biological activity during the flood event (i.e. suspended in cold flood water for several days, cf. Habersack and Moser, 2003). Characteristics typically present during shaking leaching tests (cf. Kylefors et al., 2003). However, since the waste material was ground to a particle size b0.5 mm prior to leaching, the soluble content of MSW determined by Belevi and Baccini (1989) represents an upper limit for the extractable substance load from the eroded landfill material in the flood water, even though the lower values of the presented data were used. Hence, the resulting emission loads should be seen as potential rather than actual emissions. The calculation procedure and the underlying values from Belevi and Baccini (1989) are shown in Eq. (2). S

ð2Þ

S

Discharged load of soluble substance i [kg] Soluble content of substance i as a portion of total amount (Corg: 0.007; N: 0.05; P: 0.005; Cl: 0.14; Fe: 0.0004; Cu: 0.003; Zn: 0.012; Pb: 0.0003; Cd: 0.0006)

Sm;i = Sm;i
cm;i Sm,i cm,i

Finally, it is emphasised that the emission scenario is aimed to illustrate the potential for substance releases from flooded landfills.

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Table 3 Potential emissions from the average (potentially) endangered MSW landfills during a flood event. Substance Controlled MSW landfill

Corg N P Cl Fe Cu Zn Pb Cd

Old MSW landfill

Total release Extractable amount [Mg/flood event] [Mg/flood event]

Total release Extractable amount [Mg/flood event] [Mg/ flood event]

60,000 930 250 1700 13,000 100 310 100 2.8

11,000 170 45 300 2300 19 56 19 0.5

420 46 1 234 5 0.3 4 0.03 0.002

76 8 0.2 42 1 0.06 0.7 0.006 0.0003

Hence, the selected worst case scenario serves to evaluate the potential environmental relevance of flooding MSW landfills. More sophisticated assessments can be done on a case-by-case basis for individual landfills and discrete discharge events.

4. Results and discussion The results (see Fig. 3) on flood risk exposure of Austrian MSW landfills are based on a sample of 103 controlled and 961 old MSW landfill sites, checked against a nation wide dataset about flood risk zones (HORA). With respect to the number of MSW landfill sites, one third of the controlled landfills are potentially endangered by flooding. Nearly 10% of the sites are located directly in a potential inundation area, whereas most of them are sited in a flood risk zone with a recurrence interval of 30 years. The fraction of old landfills, which is endangered by flooding, amounts to approximately 30%, with 40% of these deposits (around 12% of all old landfills) being assigned to the category endangered. Again most of these endangered sites are located in the T = 30-flood zone. Regarding the volumes of landfilled MSW exposed to flood risks, one third of controlled landfills is potentially endangered of flooding, with half of this volume being landfilled at sites categorised as endangered. This indicates that landfills, which are located in a designated flood risk zone, are on average larger than waste deposits evaluated as probably endangered. With regard to old MSW landfills, the fraction of the potentially endangered waste volume amounts to around 20% and is smaller in comparison to controlled landfills. This can partly be attributed to the fact that the largest three old landfill sites are not endangered by flooding, and that they comprise 30% of the total landfilled MSW volume. Disregarding these three sites, the portion of the potentially endangered volume increases to 27%, which is still smaller than the fraction of endangered sites referring to the number of old landfills. Hence, the potentially endangered old MSW landfills are on average slightly smaller than the probably not endangered old waste deposits. Information about flood protection measures was collected from actual or former landfill operators. The analysis of the data shows that the majority (approximately 60%) of active controlled landfills are protected by technical measures (i.e. dams) as it is requested by the Austrian Landfill Directive (cf. Austrian Landfill Directive, 2008). In particular, large landfills in flood prone areas, that are still operated, are protected against flood events of 100-year recurrence interval or higher. In contrary to operated landfills, the majority (more than 2/3) of closed sites has no flood protection at all. Altogether around 40% of potentially endangered controlled MSW landfill sites are protected against flooding. For most old MSW landfills such information was not available, as they have been operated on an informal basis. In general it must be supposed that these sites do not have provisions for technical flood protection.

For potentially endangered controlled landfills and endangered old landfills emission potentials of pollutants during a flood event are estimated for the loss of landfill stability (worst case) during flooding. The amount of potentially extractable substances from the eroded waste goods is estimated based on data presented by Belevi and Baccini (1989). The resulting emission loads are shown, exemplarily for all endangered sites, for the average potentially endangered controlled and endangered old MSW landfill (see Table 2). These two theoretical MSW landfills are presented as a generic model for floodprone waste deposits. Table 2 exhibits several differences between the average controlled and old MSW landfill, i.e. deposited waste volume, residence time, and flux of infiltrated water per year. Reported old landfills show lower infiltration rates because the majority of them are located in the drier eastern part of Austria. However, it should be noted that the samples exhibited a high heterogeneity making general statements about endangered controlled and old landfills more difficult. The emission loads estimated are summarised in Table 3. The difference between the old and controlled landfills is generally within one order of magnitude. The calculated emission loads range from a few tonnes (e.g. Cd, Pb) to many thousand tonnes (e.g. Corg, Cl), with most of the substances still being contained in the eroded waste goods. The extractable emission load amounts to a few kilograms for cadmium or up to a few hundred tonnes for organic Carbon or Chlorine. However, by calculating potential emission levels it is not possible to evaluate their environmental relevance. The environmental impacts of the released pollutants depend on the dilution potential during the flood, the availability of these pollutants (i.e. speciation, solutes, particles…), and the vulnerability of the affected environment. These factors can only be evaluated individually for each landfill and flood event. Hence, the potential pollution of a river system as a consequence of flooding an endangered landfill is discussed via a case study below. In August 2005 a major flood event due to intense rain occurred at several rivers in the western part of Austria. During this event an extreme flood, above the 100 year recurrence-interval flood, took place at the Alfenz, an alpine river with a catchment area of 172 m2 (Krapesch and Habersack, 2008). The peak discharge of the flood was around 190 m3 per second with an estimated total water load of approximately 5 million m3. The latter estimate is based on the sum of precipitation in the catchment before and during the flood (Vorarlberg, 2005b) and estimated runoff coefficients for the Alfenz catchment area (Fürst and Hörhan, 2007). Several old landfills sited adjacent to the river bed of the Alfenz were affected by this flood (Vorarlberg, 2005b). One of these MSW deposits with a volume of approximately 25000 m3 and an average age of around 30 years was completely eroded during the flood event. Based on the scenario calculations above, the emission load from this landfill into the river would be roughly one third of the emissions calculated for the average endangered old MSW landfill (cf. Table 3). The resulting substance concentrations in the flood water exceed the Austrian water quality standards for discharge into rivers (Ordinance on water discharge emissions, 1996) by up to two orders of magnitude (except for cadmium which barely complies with the emission standards) as far as the total amount of the released substances is concerned. Excluding the substances contained in the eroded waste goods results in drastically lower concentrations (cf. Table 3) easily

Table 4 Pollutant concentrations in receiving flood water. Concentration in Alfenz river

Landfill erosion (extractable)

WWTP

Limit value for discharge into rivers⁎

TOC [mg/l] Nitrogen [mg/l] Phosphorus [mg/l]

4.72 0.50 0.01

0.58 0.21 0.03

25 11⁎⁎ 2

⁎Ordinance on water discharge emissions, 1996. ⁎⁎Values for NH4-N and NO2-N (no designated value for NO3-N).

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complying with the above mentioned standards (see Table 4). However, it should be noted that these limits refer to the concentrations in landfill leachate and not to those in the receiving water body. Close to the landfill site a waste water treatment plant (WWTP) with a population equivalent of 62,500 was also flooded during the same event, resulting in a pollutant load for Corg and N that is below the calculated amount of extractable Corg and N from the eroded waste (see Table 4). The released load of P from the WWTP is even higher than the extractable emission load from the landfill. As the flood water had adverse effects on downstream water supply systems (i.e. increased levels of organic pollutants and faeces bacteria (cf. Vorarlberg, 2005b)), it can be assumed that apart from the landfill also other sources contributed substantially to the increased pollutant concentrations in the flood water. Hence, the eroded landfill site certainly increased the pollution levels in the flood water, but from an environmental point of view the eroded MSW landfill was one out of numerous potential pollutant sources adjacent to the river. This underlines that the cumulative emission load from different sources is of major importance for the resulting flood water quality. Reports about environmental pollution associated with major flood events indicate that emissions originating from MSW landfills are of environmental concern (see above). However, as a single source of pollutants MSW landfills are in most cases probably not a major environmental hazard during flooding. Large landfills with high emission potentials are commonly engineered systems and therefore less vulnerable to complete erosion than small old landfills formerly operated as open dumps. Hence, to destabilise endangered landfilled sites with high emission potentials also the erosive power of a discharge event needs to be very high, which is generally associated with high dilution potentials. Apart from that, during such disastrous events also emissions from other sources affected by flooding (e.g. waste water treatment plants, canal systems, industrial sites) increase, qualifying landfill flooding as one amongst other pollutant sources during such an event. Nevertheless, the cumulative effect of the various releases may be of major environmental concern, but this can only be evaluated on a site-specific basis in consideration of potentially affected ecosystems and vulnerable uses.

5. Conclusion Flooding of MSW landfills has been observed during major flood events, resulting in the contamination of surface water, groundwater, and soil. Within the present study a methodology to evaluate the flood risk exposure of MSW landfill sites using flood hazard maps is presented. Although the approach is developed for Austrian conditions, it can be applied in other countries, too. Region wide flood mapping projects (cf. Merz et al., 2008) are a prerequisite to estimate the flood risk exposure of landfills. For Austria the results of the study indicate that around 30% of the MSW landfills are at risk of being submerged in case of a flood with a recurrence interval of less than 200 years. Most of these sites (around 95%) are not sufficiently protected against flooding. Because there is a lack of information concerning the substance release from flooded MSW landfills, potential emissions during a flood event were investigated by a worst case scenario assuming total landfill erosion. The emission levels are calculated for the total substance inventory released as well as for the potentially soluble fraction of these substances. It is illustrated that the emission potential of flooded landfills is generally high, but with respect to the extractable part of pollutants (i.e. those released from the waste goods) a flooded landfill will in most cases be one amongst many potential pollutant sources adjacent to the river. Although the cumulative level of pollutants in the flood water is often of environmental concern, emissions from MSW landfills on their own are probably not a major environmental hazard during flooding.

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However, there are numerous uncertainties and knowledge gaps with respect to flooded landfills. Efforts should be made to gain more knowledge about the geotechnical properties of (previously unsaturated) waste bodies that are saturated with water (e.g. pore water pressure, shear strength of landfilled waste in dependence of the water content), and the environmental impacts of pollutants emitted during a flood. Apart from that in many cases landfills endangered by flooding might be inundated but not eroded during a flood event. The subsequent water saturation of a landfill body may have a significant impact on post-flooding landfill metabolism and might be of interest from the perspective of landfill aftercare. Hence, because many landfills are potentially endangered by flooding, the latter aspect is subject to further investigations. Acknowledgements This project was funded by the Federal Ministry of Transport, Innovation and Technology within the framework of the KIRAS Safety Research Program. Additional support was provided by the Federal Ministry of Agriculture, Forestry, Environment and Water Management. We would also like to thank our collaborator within this project Clemens Neuhold for assisting with the GIS queries. References Agamuthu P. Post-closure of landfill: issues and policy. Waste Manage Res 2006;24:503–4. ALSAG. Altlastensanierungsgesetz. Austrian Parliament BGBl. Nr. 1989;299. Anderson RL. Earthquake related damage and landfill performance. Earthquake Design and Performance of Solid Waste Landfills, vol 54. ASCE Geotechnical Special Publication; 1995. p. 1-16. Austrian Landfill Directive. Deponieverordnung; 2008. Baccini P, Henseler G, Figi R, Belevi H. Water and element balances of municipal solid waste landfills. Waste Manage Res 1987;5:483–99. Belevi H, Baccini P. Long-term behaviour of municipal solid waste landfills. Waste Manage Res 1989;7:43–56. Blight GE, Fourie A. Catastrophe revisited — disastrous flow failures of mine and municipal solid waste. Geotech Geolog Eng 2005;23:219–48. Bogner J, Spokas K. Landfill CH4: rates, fates, and role in global carbon cycle. Chemosphere 1993;26:369–86. Burgenland. Umwelterklärung des Burgenländischen Müllverbandes, Oberpullendorf; 2005. Christensen TH, Kjeldsen P, Lindhardt B. Gas-generating processes in landfills. In: Christensen TH, editor. Landfilling of waste: biogas. London: E&FN Spon; 1996. p. 27–44. Clevers JGPW, Kooistra L, Salas EAL. Study of heavy metal contamination in river flood-plains using the red-edge position in spectroscopic data. Int J Remote Sens 2004;25:883-3895. Curtis JA, Whitney JW. Geomorphic and Hydrologic Assessment of Erosion Hazards at the Norman Municipal Landfill, Canadian River Floodplain, Central Oklahoma. Environ Eng Geosci 2003;9:241–53. Döberl G, Huber R, Fellner J, Cencic O, Brunner PH. Neue Strategien zur Nachsorge von Deponien und zur Sanierung von Altlasten (Projekt STRANDEZA). Abteilung Abfallwirtschaft und Stoffhaushalt, Technische Universität Wien; 2002. p. 267. Ehrig HJ, Krümpelbeck I. The emission behaviour of old landfills in the aftercare phase. In: Christensen TH, Cossu R, Stegmann R, editors. Proceedings Sardinia 2001, Eigth International Waste Management and Landfill Symposium. IV. CISA, S. Margherita di Pula; 2001. p. 313–23. Flögl W. Klimarelevanz der Deponien in Oberösterreich. Dr. Flögl Hydro Consulting Engineers, Linz; 2002. Gandolla M, Gabner E, Leoni R. Stabilitätsprobleme bei nicht verdichteten Deponien: am Beispiel Sarajevo (Stability Problems with Compacted Landfills: the Example of Sarajevo). ISWA J 1979. Geller W, Ockenfeld K. Schadstoffbelastung nach dem Elbe-Hochwasser 2002. In: Böhme M, Knöchel A, editors. Final report of the ad-hoc-project 'Schadstoffuntersuchungen nach dem Hochwasser vom August 2002 — Ermittlung der Gefährdungspotentiale an Elbe und Mulde'. UFZ — Umweltforschungszentrum LeipzigHalle GmbH,, Magdeburg; 2004. Habersack H, Moser A. Ereignisdokumentation — Hochwasser August 2002. Final Report. University of Natural Resources and Applied Life Sciences, Vienna; 2003. p. 184. Fürst J, Hörhan T. Hydrological Atlas Austria. Vienna: Lebensministerium; 2007. Kärnten. Kärntner Abfallbericht und Abfallwirtschaftskonzept. Amt der Kärntner Landesregierung, Abteilung 15 — Umweltschutz und Technik, Klagenfurt; 2000. Kjeldsen P, Christophersen M. Composition of leachate from old landfills in Denmark. Waste Manage Res 2001;19:249–56. Klink RE, Ham RK. Effects of moisture movement on methane production in solid waste landfill samples. Resour Conserv 1982;8:29–41. Kocasoy G, Curi K. The Umraniye–Hekimbasi open dump accident. Waste Manage Res 1995;13:305–14. Krammer HJ, Domenig M, Striedner J, Vogel G. Materialien zum Bundesabfallwirtschaftsplan (BAWP), Band 3: Kommunale Abfälle. Bundesministerium für Umwelt, Jugend und Familie, Wien; 1992. p. 180.

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