Flood Episodes Research Articles

Palaeoflood events during the last deglaciation in the Yellow River source area on the northeast Tibetan Plateau

Palaeoflood records have provided the extended perspective required to understand linkages between extreme floods and climate variability. During our palaeo‐hydrological investigations, two units of palaeoflood slackwater deposits (SWD) were found on the river banks in the Maqu‐Oula reach along the mainstream of the Yellow River on the northeast (NE) Tibetan Plateau. A series of samples were taken from the sediment profiles at Taiwuruo (TWR) and Daerqiong (DEQ) sites for laboratory analysis. Grain‐size distribution and micro‐morphological characteristics of quartz grains indicate that these well‐sorted SWD units were derived from the suspended sediment load in floodwater. They have recorded two episodes of overbank flooding in the Yellow River source area. Using the optically stimulated luminescence (OSL) dating technique, the first episode of overbank flooding was dated to 13.6–13.0 ka and correlated with the Bølling–Allerød warm interval of the last deglaciation. The second episode occurred at 11.0–10.0 ka, that is, the early Holocene. In a warm‐humid climate, these overbank flooding episodes may have resulted from the accelerated melting of mountain glaciers and snow over the headwaters of the alpine and subalpine regions on the NE Tibetan Plateau. These results are important in facilitating an in‐depth understanding of the hydro‐climatic response of the Tibetan Plateau to global climate warming occurring presently.

The flood of October 9, 2018 in the city centre of Sant Llorenç des Cardassar (Mallorca)

Since the 1940s, the city centre of Sant Llorenç des Cardassar has suffered from several flooding episodes from the several tributaries of ca n’Amer creek. Five lives lost and a significant impact on the population were the result of the most relevant flood in the series that occurred in 2018. In this paper, an analysis of the historical relationship of the village with floods, the answer provided by the administration to those floods, and the geographic setting and the anthropic actions on the land are considered. Using the data collected by direct observation, witnesses, and graphs and fieldwork, a thorough investigation of the volume, flow, direction and levels of water has been developed. This translates into an exhaustive mapping of the event, discriminating the hydraulic behaviour in each of the affected roads and showing the sequential development of the flood. Flooding is a combination of severe stream flows, avulsion processes and angular sections that combine with infraestructures that interfere with the flow direction and prevent its reintegration into the main channel and where the streets become active channels.

What can we learn from the past? A century of changes in vulnerability to floods in the Ter River basin

The objective of this article is to analyze from a historical perspective the impacts of floods in the Ter river basin of North-Eastern Catalonia between 1900 and 2020. The analysis focuses on the three factors that, according to the IPCC, intervene in the definition of vulnerability, namely exposure, susceptibility and adaptive capacity. The analysis has been structured in four historical periods with two or three catastrophic flood episodes for each period. Although a lack of reliable data and studies on especially economic losses must be acknowledged, results obtained indicate that flood exposure has increased in the basin but vulnerability may have decreased as a result of decreased susceptibility and, especially, of a significant increase in adaptive capacity. Both in terms of victims and relative economic losses, the impacts of the floods would show a downward trend that, among other factors, tends to correlate positively with the increasing levels of economic development and well-being experienced in the basin during the last century.

Biochar-amended coastal wetland soil enhances growth of Suaeda salsa and alters rhizosphere soil nutrients and microbial communities

Biochar has the potential to improve soil properties and increase plant productivity. However, due to the different types of soil, plants, and environmental factors, the impact of biochar is likely to vary. We explored the impacts of biochar prepared from an invasive plant Spartina alterniflora on plant performance and soil characteristics in a simulated coastal wetland ecosystem. We investigated the impact of three application ratios (control, 1%, and 5%; weight ratio) of biochar on the germination and growth of a native plant Suaeda salsa, the nutrient content and microbial community characteristics of the rhizosphere soil under three flooding treatments (no flooding, episodic flooding, and continuous flooding). Biochar application had no impact on seed germination of S. salsa, but promoted its seedling growth (biomass, height, root length) and nitrogen content. Biochar application also enhanced soil nutrient content and affected soil microbial community characteristics. Seed germination and seedling growth of S. salsa were sensitive to flooding and were the best under episodic flooding. Notably, flooding inhibited the impact of biochar on S. salsa and rhizosphere soil. In conclusion, biochar can positively affect the growth of S. salsa and improve the quality of rhizosphere soil, especially under no flooding. Our findings highlight the possibility of applying biochar for the restoration of S. salsa in coastal wetlands.

Palaeohydraulic reconstruction and depositional model of the episodic flooding channels developed in the modern arid alluvial fan: Implications for the exploration target of the heterogeneous alluvial fan reservoirs

Alluvial fan reservoirs associated with episodic flood flows are generally heterogeneous, both laterally and vertically, owing to the variable depositional conditions and mechanisms. The complexity of sedimentary processes results in distinct challenges in terms of reservoir characterization and subsurface modelling. The ability to discern fan deposits in the subsurface directly impacts the assessment of the distribution, physical properties, and hydrocarbon recovery of reservoirs. Taking the Quaternary Poplar Fan as an example, this study aims to determine the characteristics, depositional model, and controlling factors of the episodic flooding channels developed in an alluvial fan through palaeohydraulic reconstruction. These research topics have rarely been studied and are poorly understood. The Poplar Fan is dominated by coarse conglomerates from apex to toe. In particular, lenticular gravelly and sandy flooding channel deposits can be identified throughout the fan and are easily distinguishable from the surrounding sheet-like conglomerates of the incised channel flood, sheetflood, and unconfined streamflood deposits in outcrops. Such flooding channels are characterized by the absence of fine-grained floodplain deposits or overbank deposits and the lack of in-channel mudstone drapes or plugs. This indicates the short-lived and episodic nature of the sedimentation processes. Individual channels are ribbon-shaped, with width/thickness ratios of less than 15:1, and show limited amalgamated characteristics. The estimated palaeoslopes of these flooding channels are all above the maximum gradient for modern typical rivers. In particular, the width, thickness, maximum particle size, calculated bankfull discharge, and stream power of these preserved channels all exhibit a decreasing downstream trend. Additionally, the channel width/thickness ratios increase initially and then decrease from the proximal to the distal fan. Accordingly, these episodic flooding channels predominately exhibit a distributary pattern in the plan view. Moreover, 70% of the estimated channel length is less than the maximum radial length of the fan, which suggests that these episodic flooding channels may gradually disappear downstream. Based on these outcrop data, a depositional model, together with an evolution pattern of the in-fan episodic flooding channels, was established. The variations in the water and sediment concentrations of the flood flow could be the major cause of the cyclic transformations between the episodic sheet-like and channelised flooding processes. Notably, compared with the sheet-like flood flow deposits, these episodic flooding channel deposits are much more organized in gravel arrangement, well-sorted, and more homogeneous, consequently having better physical properties and constituting a favourable exploration target. Moreover, the proposed cyclic evolution model of the episodic flooding channel can provide effective guidelines for stratigraphic correlation in characterizing heterogeneous alluvial fan reservoirs. The lithofacies and reconstructed palaeohydraulic parameters from the outcrops can also provide reasonable parameters and references for underground reservoir modelling and core analysis.

The 2019/2020 floods in the UK: a hydrological appraisal

The 2019/2020 floods in the <scp>UK</scp>: a hydrological appraisal

Attraction in the Dark: The Magnetism of Speleothems

No matter how quiet and pristine a cave setting may appear, all speleothems contain assemblages of magnetic minerals. These iron oxide minerals are derived largely from overlying soils, though minor fractions may come from the residuum of dissolved bedrock, reworked sediment carried by episodic floods, geomicrobiological activity, and even windblown dust. Regardless of their origin, these minerals become aligned with Earth’s ambient magnetic field before they are fixed within a speleothem’s growing carbonate matrix. Here, we describe how the magnetism of stalagmites and flowstone can be used to chronicle high-resolution geomagnetic behavior and environmental change.

Flood susceptibility mapping by integrating frequency ratio and index of entropy with multilayer perceptron and classification and regression tree

Episodes of frequent flooding continue to increase, often causing serious damage and tools to identify areas affected by such disasters have become indispensable in today's society. Using the latest techniques can make very accurate flood predictions. In this study, we introduce four effective methods to evaluate the flood susceptibility of Poyang County, in China, by integrating two independent models of frequency ratio and index of entropy with multilayer perceptron and classification and regression tree models. The flood locations of the study area were identified through the flood inventory process, and 12 flood conditioning factors were used in the training and validation processes. According to the results of the linear support vector machine, elevation, slope angle, and soil have the highest predictive ability. The experimental results of the four hybrid models demonstrate that between 20% and 50% of the study area has high and very high flood susceptibility. The multilayer perceptron-probability density hybrid model is the most effective among the six comparative methods.

Late-Holocene evolution of the Northern Bay of Cádiz from geomorphological, stratigraphic and archaeological data

The present paper deals with the historical evolution of the northern Bay of Cádiz (SW Spain) between the last eustatic maximum (6.5 ka BP) and the present day, by means of a series of independent proxies. The zone is constituted by the tidal estuary of the Guadalete River, filled with saltmarsh sediments during the late Holocene, due to the sheltering of the zone by a confining outer sandy barrier. The northern border of the Bay records an urban settlement of Phoenician Age (first millennium BC), Doña Blanca. A detailed survey was made in the contact between the Phoenician city and the saltmarshes in order to detect other possible urban structures related to the morphological and sedimentary evolution of this environment during historical times. Two campaigns with GPR Stream-X array were carried out as well as aerial imaging and topographic survey with UAV. In parallel, a total of 8 boreholes were made in different parts of the saltmarshes, including radiocarbon dating of selected samples for estimating sedimentation rates in the saltmarshes. Results obtained by georadar prospection and UAV survey revealed the presence of a second urban settlement on the marginal sedimentary plain, very probably installed upon a sandy fluvial island of the Guadelete River. The urban remains, of Punic Age, are partly covered by clay sediments due to the subsequent evolution of these saltmarshes, where sedimentation rates of up to nearly 2.4 mm/yr have been estimated for environments close to fluvial and/or tidal channels and hence more affected by sediment aggradation during flooding episodes. In recent times, river regulation by dams and the artificial desiccation and cropping of the saltmarshes have interrupted the natural trend of the area towards sedimentary silting up.

Miocene Atlantic transgressive - regressive events in northeastern and offshore Patagonia: A palynological perspective

Key information for regional biostratigraphic, climatic and environmental reconstructions for the Miocene of the southwestern Atlantic margin can be obtained by qualitative and quantitative palynological analysis at the onshore YPF-CH-PV.es-1 borehole (PV borehole) in the Valdés Basin, combined with previously documented organic-walled dinoflagellate cyst data from the Colorado Basin and well-dated outcropping sections on the east coast of Patagonia. A sequence of eleven significant dinocyst bioevents (highest occurrence, HO; highest common occurrence, HCOs) is recognized across the Valdés and Colorado basins. The bioevents occur in the same stratigraphic order and seem to be synchronous across both basins. From the oldest to the youngest, these are: HO of Emmetrocysta urnaformis, HO of Cannosphaeropsis quattrocchiae, HCO and HO of Hystrichokolpoma rigaudiae, HO of Cousteaudinium auybriae, HCO and HO of Dapsilidinium pseudocolligerum, HO of Cleistosphaeridium ancyreum, HO of Labyrinthodinium truncatum, HO of Operculodinium piaseckii and HO of Reticulatosphaera actinocoronata. The presumed climatically-driven extinctions of Dapsilidinum pseudocolligerum and Hystrichokolpoma rigaudiae around the Burdigalian to earliest Langhian, may be linked to global cooling and the re-establishments of the Antarctic ice-sheets since ~14 Ma. Two maximum flooding episodes, characterized by warm, outer (distal) neritic environmental conditions were identified at the PV borehole, presumably related to glacio-eustatic sea level rise. The older occurred in the Burdigalian – earliest Langhian and the younger, in the Tortonian. The latter maximum flooding is followed by environmental and/or climatically-driven change, implying abrupt shifting from neritic to nearshore conditions, the extinction of the warm-water taxa, and dinocysts being largely replaced by acritarchs.

High‐resolution flood precipitation and streamflow relationships in two US river basins

AbstractRelationships between rainfall and river discharge are important for governing flood characteristics and predicting flood impacts. Previous studies have examined these relationships, but they lacked the high‐resolution precipitation data necessary to analyse rainfall–streamflow correlations for individual flood episodes. The present study addresses this limitation by examining rainfall–streamflow relationships in two topographically and climatically different river basins: the Wabash River basin in Indiana and the Willamette River basin in Oregon, using high‐resolution, sub‐basin precipitation and discharge data. Results show that flood rainfall–streamflow relationships are highly spatially variable on a sub‐basin scale. In the Wabash basin, strong positive correlations exist between rainfall and streamflow near urban areas and slight terrain gradients during flash floods, while weaker correlations between rainfall and streamflow are observed in other areas of the basin and for slow‐rise floods. In the Willamette basin, strong positive slow‐rise flood rainfall–streamflow relationships occur in referenced gauges in the eastern, mountainous part of the basin, while strong negative correlations occur in non‐referenced gauges near reservoirs along the main rivers. Results suggest that in addition to high‐resolution rainfall variability, the influence of urbanization, topography and water management on flood rainfall–streamflow relationships needs to be considered in order to forecast local flood impacts better.

Outbreaks of epizootic ulcerative syndrome in Kerala, India following episodes of flooding.

Large-scale fish mortality was observed in flood-affected fish farms across several parts of Kerala following heavy rainfall in August 2018 and 2019-nearly 53% above the normal monsoon rain that the region receives. The affected fish had severe haemorrhages and ulcers, typical of the highly infectious disease epizootic ulcerative syndrome (EUS) caused by the water mould Aphanomyces invadans. In freshwater, snakeheads Channa spp. and in brackish water mullet (Mugilidae) and pearl spot (Etroplus suratensis) were severely affected. EUS was observed in 4 freshwater fishes for the first time: dotted sawfin barb Pethia punctata (Cyprinidae), Malabar leaffish Pristolepis malabarica (Pristolepididae), mahecola barb Puntius mahecola (Cyprinidae) and giant snakehead Channa pseudomarulius (Channidae). Histology and molecular diagnosis confirmed the cause of mortality to be EUS. Fungal hyphae were also observed in deeply ulcerated fish, revealed by lactophenol cotton blue staining. The severity of the EUS outbreak was linked to the sudden change in water quality associated with the flood, such as lower water temperature, and decreases in pH, total alkalinity and total hardness.

Soil Moisture Responses Associated with Significant Tropical Cyclone Rainfall Events

Several historic rainfall and flooding events associated with Atlantic Basin tropical cyclones have occurred in recent years within the conterminous United States: Hurricane Joaquin (2015) in early October over South Carolina; Hurricane Harvey (2017) in late August over southeastern Texas; Hurricane Florence (2018) in September over North Carolina; and Tropical Storm Imelda (2019) in September, again over southeastern Texas. A common attribute of these events includes a dramatic transition from dry soils to exceptional flooding in a very short time. We use an observations-driven land surface model to measure the response of modeled soil moisture to these tropical cyclone rainfall events and quantify the soil moisture anomalies relative to a daily, county-based model climatology spanning 1981 to 2013. Modeled soil moisture evolution is highlighted, including a comparison of the total column (0-2 m) soil moisture percentiles (derived from analysis values) to the 1981-2013 climatological database. The South Carolina event associated with Hurricane Joaquin resulted in a sudden transition from severe drought to significant flooding in the span of a few days, due to locally 700+ mm of rainfall. The prolonged heavy rainfall associated with Hurricane Harvey resulted in record soil moisture values well in excess of the tail of the climatological distribution. The soil moisture west of the Houston, Texas, metropolitan area was anomalously dry prior to Harvey, but quickly transitioned to near saturation in the top 1 m, while east of the Houston area antecedent soil moisture values were more moist prior to the local 1200+ mm of rainfall and catastrophic flooding in the Beaumont/Port Arthur area. Hurricane Florence led to widespread 500-700+ mm of rainfall in North Carolina, and another dramatic transition from anomalously dry conditions to record wetness. Once again, with Tropical Storm Imelda, portions of southeastern Texas experienced extreme rainfall amounts up to 1000+ mm, resulting in another sharp transition from drought conditions to extreme flooding in &lt;3 days. An experimental forecast soil moisture percentile is presented for the Imelda event, showing the potential to increase situational awareness for upcoming flooding episodes, along with a discussion of how an ensemble-based approach could be explored to address forecast model error and uncertainty.

Soil Moisture Responses Associated with Significant Tropical Cyclone Rainfall Events

Several historic rainfall and flooding events associated with Atlantic Basin tropical cyclones have occurred in recent years within the conterminous United States: Hurricane Joaquin (2015) in early October over South Carolina; Hurricane Harvey (2017) in late August over southeastern Texas; Hurricane Florence (2018) in September over North Carolina; and Tropical Storm Imelda (2019) in September, again over southeastern Texas. A common attribute of these events includes a dramatic transition from dry soils to exceptional flooding in a very short time. We use an observations-driven land surface model to measure the response of modeled soil moisture to these tropical cyclone rainfall events and quantify the soil moisture anomalies relative to a daily, county-based model climatology spanning 1981 to 2013. Modeled soil moisture evolution is highlighted, including a comparison of the total column (0-2 m) soil moisture percentiles (derived from analysis values) to the 1981-2013 climatological database. The South Carolina event associated with Hurricane Joaquin resulted in a sudden transition from severe drought to significant flooding in the span of a few days, due to locally 700+ mm of rainfall. The prolonged heavy rainfall associated with Hurricane Harvey resulted in record soil moisture values well in excess of the tail of the climatological distribution. The soil moisture west of the Houston, Texas, metropolitan area was anomalously dry prior to Harvey, but quickly transitioned to near saturation in the top 1 m, while east of the Houston area antecedent soil moisture values were more moist prior to the local 1200+ mm of rainfall and catastrophic flooding in the Beaumont/Port Arthur area. Hurricane Florence led to widespread 500-700+ mm of rainfall in North Carolina, and another dramatic transition from anomalously dry conditions to record wetness. Once again, with Tropical Storm Imelda, portions of southeastern Texas experienced extreme rainfall amounts up to 1000+ mm, resulting in another sharp transition from drought conditions to extreme flooding in &lt;3 days. An experimental forecast soil moisture percentile is presented for the Imelda event, showing the potential to increase situational awareness for upcoming flooding episodes, along with a discussion of how an ensemble-based approach could be explored to address forecast model error and uncertainty.

Flood disasters and management in Ughelli and environs, Delta State, Nigeria

The study examines the 2022 floods disasters in Ughelli and environs, Nigeria. Field survey of 25 communities affected by flood disaster in Ughelli north and south Local Government Areas (LGA) were carried to measure the inundated areas and their levels (depth). Questionnaires were also administered to solicit the causes, effect of flood, and management strategies adopted during the flood episodes. Data were presented and analyzed with statistical diagrams and descriptive statistics. Results revealed high level of flood inundation and disasters in Ughelli north and south of Delta State, with a colossal and devastating damage on properties and lives. Properties worth 616.3 million and 573 million of worth of crops were destroyed. And socioeconomic activities come to a standstill. Heavy rainfall, release of water from Lagdo dam in Cameroun amongst others are the causal factors of the disaster. The study posited building of buffer dams, adhering to NiMet weather prediction, and planning regulations among others as the flood management options.

Dynamic maps of human exposure to floods based on mobile phone data

Abstract. Floods are acknowledged as one of the most serious threats to people's lives and properties worldwide. To mitigate the flood risk, it is possible to act separately on its components: hazard, vulnerability, exposure. Emergency management plans can actually provide effective non-structural practices to decrease both human exposure and vulnerability. Crowding maps depending on characteristic time patterns, herein referred to as dynamic exposure maps, represent a valuable tool to enhance the flood risk management plans. In this paper, the suitability of mobile phone data to derive crowding maps is discussed. A test case is provided by a strongly urbanized area subject to frequent flooding located on the western outskirts of Brescia (northern Italy). Characteristic exposure spatiotemporal patterns and their uncertainties were detected with regard to land cover and calendar period. This novel methodology still deserves verification during real-world flood episodes, even though it appears to be more reliable than crowdsourcing strategies, and seems to have potential to better address real-time rescues and relief supplies.

Combining Instrumental Monitoring and High-Resolution Topography for Estimating Sediment Yield in a Debris-Flow Catchment

ABSTRACT In mountain basins, long-term instrumental monitoring coupled with high-resolution topographic surveys can provide important information on sediment yield. The Gadria catchment, located in the eastern Italian Alps, typically features several low-magnitude flood episodes and a few debris-flow events per year, from late spring to late summer. Beginning in 2011, sensors devoted to debris-flow detection (geophones, video cameras, flow stage sensors) were installed along the main channel, upstream of a retention basin. In case of debris flows, high-resolution topographical surveys of the retention basin are carried out multiple times per year. Rainfall is measured in the lower part of the catchment and at the headwaters, while passive integrated transponder tracing of bedload was performed in the main channel during spring and summer 2014. In this work, we present the reconstruction of the sediment dynamics at the catchment scale from 2011 to 2017. Results show that (i) coarse sediment yield is dominated by the few debris flows occurring per year; (ii) debris-flow volume estimations may be significantly different—up to 30 percent lower—when performed through a digital elevation model of difference analysis, compared to the time-integration of the debris-flow discharge estimates; (iii) using this latter method, the volumes are affected by significant uncertainties, particularly for small values of flow depth; and (iv) rainfall analysis permits us to characterize debris-flow initiation but also highlights difficulties in discriminating triggering from non-triggering rainstorms if based on rainfall duration and intensity only.

ASSESSMENT OF VADOSE ZONE CHARACTERISTICS FOR ENVIRONMENTAL IMPACT AUDIT OF SELECTED CEMETERIES AROUND OSUN STATE, SOUTH-WESTERN PART OF NIGERIA

Cemeteries have been identified as a possible source of groundwater and environmental pollution. This may be due to wrong siting of cemeteries, poor soil selection and very thin vadose zone. Over the years, most communities around Osun State experience a number of communicable diseases like dysentery, diarrhea and typhoid, especially after episodes of flash floods. Therefore, this study was carried out to audit the impact of burial practices on the immediate environment viz-a-viz their interaction with both surface and groundwater which forms the main source of potable water for the communities. Method of approach include; assessing possible water contamination, studying the vadose hydrological characteristics as well as studying the geotechnical properties of soils within the vadose zone. Water samples from the vicinity of both cemeteries shows probable contamination with an average pH of 6.19 for Ede and 6.57 for Iragbiji, EC with an average 480μS for Ede and 1210μS for Iragbiji. Biological constituents found within the area include; enterobacteriaceae (salmonella spp., serratia spp., proteus spp., shigella spp.), suggesting likely contamination of both surface and groundwater around the vicinity of the cemeteries. Most cations and anions analysed for (Mg2+, NO3-, SO42-, and PO43-) comply with the WHO standards based on their maximum permissible limits (MPL). Geotechnical investigations revealed that soils within the study areas are largely unsuitable for a standard cemetery due to their high moisture content, poor grading characteristics, low compaction value, poor hydraulic characteristics and shallow water level. The study concluded that cemeteries from both towns have a negative impact on their immediate environment due to poor selection of soil materials (porous and permeable sandy soil) as reflected in the quality of surface and groundwater.

Green roof for sustainable urban flash flood control via cost benefit approach for local authority

People migration to urban region have created dense opaque urban landscape which generates high volume of storm water runoff and frequent flash flood episodes. This has caused tremendous damages and loss to the nation. Local authority has to spend greatly to repair damages caused by this disaster. Studies have proven that green roof acts as an efficient green infrastructure to control storm water runoff and hindrance flash flood occurrences. However, the worth of implementing green roof for the local authority remains unrevealed. This study prompts to assess the economic worth of implementing green roof for the local authority using costs benefits analysis. Overall, extensive green roof provides better cost benefits ratio than intensive green roof whereby the benefit is 1.2–3.5 times larger than green roof cost. Roof slope contributes the highest benefit ratio for intensive green roof at 2 times higher than minimum cost. Meanwhile, vegetation provides the largest benefit ratio for extensive green roof at 4.2 times larger than minimum cost. Green roof has proven to be worthy for local authority from the economic and environment aspects. This is significant in creating a new pathway to encourage sustainable practice among local authority thus serve national sustainable development agenda.

Potential Release of Zinc and Cadmium From Mine-Affected Soils Under Flooding, a Mesocosm Study

Metal-contaminated mining soils pose serious environmental and health risks if not properly managed, especially in mountainous areas, which are more susceptible to perturbation. Currently, climate change is leading to more frequent and intense rain events, which cause flooding episodes, thereby altering soil redox equilibria and contaminants stability. We evaluated the potential release of Zn and Cd (two of the most common inorganic contaminants) and the factors regulating their solubility and speciation in two heavily contaminated soils representative of a Zn-mining area. The soils were flooded under aerobic (for 24 h) and anaerobic (for 62 days) conditions using mesocosm experiments, sequential extractions, and geochemical modelling. Leaching trials under aerobic conditions showed a high release of Zn and Cd (10 times the legislative limits), with metals possibly migrating via water infiltration or runoff. Under anaerobic conditions Zn and Cd were initially released. Then, solution concentrations decreased gradually (Zn) or sharply (Cd) until the end of the experiment. Sequential extractions and multisurface modelling indicated that both metals precipitated mainly as carbonates. This was confirmed by a geochemical multisurface modelling, which also predicted the formation of sulphides after 60 days in one soil. The model calculated metals to be preferentially complexed by organic matter and well predicted the observed soil solution concentrations. The results showed that during flooding episodes contaminants could be promptly transferred to other environmental compartments. The use of multisurface modelling coupled with laboratory experiments provided useful indications on the potential release and speciation in case of anoxic conditions.