Non-flooded Areas Research Articles

Rainfall patterns and geomorphological controls driving inundation frequency in tropical wetlands: How does the Pantanal flood?

The Pantanal is one of the world’s largest freshwater wetlands. The spatial and temporal variability of flooded areas is a key factor for preserving and managing the flora and fauna of this biodiversity hotspot, and thus, its dynamic is crucial to maintain ecosystem services. However, existing inventories of flooded areas with high spatial resolution are scarce or do not represent a continuous time series considering the entire Pantanal wetland. In this study, flooded areas were derived from Landsat and Resourcesat satellite imagery time series for the years 2000 to 2020 through big data analytical tools. Our results show that permanently flooded areas accounted for 3.40% of the total Pantanal wetland and 8.85% of the study area was flooded during only one year, indicating a complex and dynamic fluvial system. In addition, approximately 39% of the basin was composed of non-flooded areas. During the analyzed period (2000–2020), the highest flood event occurred in 2011 covering an area of 57,969 km2, followed by 2014, with 52,500 km2 (respectively 38.55% and 34.91% of the total area of the Pantanal). The year with the smallest flooded area was 2020 (10,668 km2), 83% lower when compared to the period-based average. The Pantanal is a seasonal wetland, thus, rainfall plays a significant role in the flood pulse, accounting for approximately 60% of the total variability of the flooded areas. The flood dynamics is also affected by the morphology of the modern depositional system of the Pantanal, which is composed by large megafans created by several distributive rivers, and by neotectonics that generates differential movements of blocks creating lower areas that will determine how flood pulse moves spatially and temporally. Therefore, the understanding and analysis of this dynamism becomes an indispensable tool for the public government ordering defining policies for the occupation and the economic zoning of the Pantanal.

Mapping Flood Risk of Nsanje District in Malawi Using Sentinel-1 Data

The all-time imaging ability of SAR systems which can penetrate cloud cover and free availability of Sentinel C-Band data are very useful in deriving critical spatial information for flood disaster management in tropical areas such as Malawi. This study shows how Sentinel-1 data has been used to map flood extents by utilizing VH and VV polarizations and enhance risk mapping during the years 2015 to 2020 in Nsanje district. Multi-dated Sentinel-1 images were acquired, pre-processed, and analyzed through Change Detection and Thresholding technique to interpret backscattered radiation thereby distinguishing flooded and non-flooded areas. The VV Polarization result shows that percentage of land that remained under flood water in Nsanje district was 3.97% in 2015, 5.91% in 2019 and 2.05% in 2020. On the other hand, VH Polarization result shows about 7.71% and 2.02% of land remained under flood water in 2019 and 2020 respectively.Sentinel-2 pre-flood image was used to determine major land cover classes in the district. MNDWI derived from Landsat 8 imagery of the same date as 2019 Sentinel-1 crisis imagery was used for flood extent validation. Overall Accuracy of flood extent delineation was 96% and 90% for VH and VV polarization respectively. Flooding frequency in specific areas was observed to determine physical vulnerability and hence figure out the risk to a possible repetition of flood disaster. Further, social data were used to aid a better understanding of the capacity to cope with a possible flood hazard in the study area.

Инженерно-геологическое районирование участка железной дороги методом вероятностной оценки классификационного показателя

The article describes the special engineering-geological zoning method of the railway territory. Permafrost geocryological conditions of the railway geological section were analyzed. The area is characterized by sporadic discontinuous permafrost. The analysis showed that the process of flooding is widely developed at the stusy area. It will have a great impact on the design and operation of the structure. The method of probabilistic assessment was used for a reasonable zonation of the territory. In result of the study, three taxa were identified that allows defining the flooded, potentially flooded, and non-flooded areas according to their geological structure. Measures for reducing the negative impact of flooding processes are recommended.

Флористичний склад і таксономічна структура водоростей гіпергалінних водойм північно-західного узбережжя Азовського моря (Україна)

The article represents the results of long-term algological studies of hyperhaline reservoirs of the northwestern coast of the Azov Sea. The features of the floristic composition and taxonomic structure of algae in aquatic (water column and bottom), aquatic-terrestrial (water’s edge, dried up water bodies, drying area) and terrestrial (elevated non-flooding areas) habitats of these objects are displayed. A specificity of the studied algoflora lies in the absence of representatives of certain characteristic phyla for the salt-water and non-saline land and water habitats of the territory of Ukraine. It was established that species composition of the studied reservoirs is depleted in comparison with other non-saline and marine ecosystems. Totally, 123 algae species were identified. They represente 7 phyla, 10 classes, 27 orders, 47 families, 68 genera. The largest number of species included three phyla: Cyanoprocaryota – 65 species (52.9% of the total number of identified species), Bacillariophyta – 26 (21.1%), Chlorophyta – 22 (17.9%). The first places among the six leading orders were taken by cyanoprocaryotes from Oscillatoriales, Nostocales, Chroococcales and diatoms from Naviculales. The most numerous species at the family level are trichomous cyanoprocaryotes from Nostocaceae, Pseudanabaenaceae, and Phormidiaceae. There were found 23 leading genera – their species richness exceeds the average indicator (1.81 species). According to the results of original studies, it was noted that all taxonomic levels of algoflora of the hyperhaline reservoirs shows features of not only saline habitats, but also of the freshwater, marine and terrestrial extreme ecosystems. Such diversity of the algal population indicates an unstable hydrological regime and complex relations of water exchange between the hyperhaline reservoirs and nearby terrestrial and aquatic habitats.

Estimating Flood Characteristics Using Geomorphologic Flood Index with Regards to Rainfall Intensity-Duration-Frequency-Area Curves and CADDIES-2D Model in Three Iranian Basins

There is not enough data and computational power for conventional flood mapping methods in many parts of the world, thus fast and low-data-demanding methods are very useful in facing the disaster. This paper presents an innovative procedure for estimating flood extent and depth using only DEM SRTM 30 m and the Geomorphic Flood Index (GFI). The Geomorphologic Flood Assessment (GFA) tool which is the corresponding application of the GFI in QGIS is implemented to achieved the results in three basins in Iran. Moreover, the novel concept of Intensity-Duration-Frequency-Area (IDFA) curves is introduced to modify the GFI model by imposing a constraint on the maximum hydrologically contributing area of a basin. The GFA model implements the linear binary classification algorithm to classify a watershed into flooded and non-flooded areas using an optimized GFI threshold that minimizes the errors with a standard flood map of a small region in the study area. The standard hydraulic model envisaged for this study is the Cellular Automata Dual-DraInagE Simulation (CADDIES) 2D model which employs simple transition rules and a weight-based system rather than complex shallow water equations allowing fast flood modelling for large-scale problems. The results revealed that the floodplains generated by the GFI has a good agreement with the standard maps, especially in the fluvial rivers. However, the performance of the GFI decreases in the less steep and alluvial rivers. With some overestimation, the GFI model is also able to capture the general trend of water depth variations in comparison with the CADDIES-2D flood depth map. The modifications made in the GFI model, to confine the maximum precipitable area through implementing the IDFAs, improved the classification of flooded area and estimation of water depth in all study areas. Finally, the calibrated GFI thresholds were used to achieve the complete 100-year floodplain maps of the study areas.

Calidad del agua subterránea y riesgos de salud asociados en las escuelas públicas afectadas por inundaciones: un estudio de caso del distrito Sanghar, Pakistán

Drinking water quality is of vital importance for the healthy life of a community especially if consumer is a teenager. In order to compare groundwater profile of flooded area (FA) and non-flooded area (NFA) of district Sanghar, 120 water samples from public schools were collected and investigated for physico-chemical parameters, essential metals, trace elements and microbiological indicators. Analysis data revealed that 47% samples in FA were contaminated with faecal coliform bacteria as compared to only 8.3% in NFA. On the other hand, chemical indicators like TDS, Ca, Na, K, SO4, Mg and hardness were higher in FA. Comparison of trace elements content with WHO guidelines revealed that concentration of Fe, As and Zn was higher in 66.7%, 31.7% and 13.3% water samples, respectively in FA whereas content of these elements was also on higher side in 3.3%, 23.3% and 1.7% samples in NFA, respectively. Health risk assessment due to high concentration of Fe, As and Zn showed that As HRI>1, for children in 35 and 23% water samples in FA and NFA, respectively.

The influence of seasonal river flooding in food consumption of riverine dwellers in the central Amazon region: an isotopic approach

In recent decades, the nutritional transition has been encroaching on remote rural areas of developing countries where feeding patterns are shifting from unprocessed foods to industrialized processed goods. Such changes in the Amazon region have been detected, for instance, by comparing the natural carbon (13C:12C) and nitrogen (15N:14N) isotopic ratios of people living in riverine communities with urban dwellers their putative diet. In this study, we considered how landscape variables impacted food consumption by comparing fingernail isotopic ratios of individuals in the rural settlement of Costa do Caldeirao located in the floodplain (varzea) of the Solimoes River, and in the rural settlement of Paquequer located in a non-flooded area (terra-firme) near the Madeira River banks. A total of 70 fingernails were sampled for carbon and nitrogen isotopic analysis during the low water period and again during the high water period from the same residents of the varzea and terra-firme. The consumption of C4-like resources (e.g., frozen chicken and canned meat) increased in both rural settlements during the high water period when C3-like resources (fish, cassava, rice, beans) are less available due to the flooding of lowland areas, but this difference was more pronounced in the terra-firme. The higher consumption of C4-like resources in the varzea compared to the terra-firme shows how seasonal flooding is a key factor influencing food security and health, due to stark variations in river water levels. While fish and farinha are still important staple foods, differences within rural settlements suggest that, besides seasonal variation and changes in water levels, other factors such as age, origin, and income may be crucial to understanding individual dietary behavior change in line with the nutritional transition model.

Spatial and temporal variability of soil moisture in non-flooded landscape units in Namibian Zambezi region

Climate variability will continue to impact the spatial and temporal variability of soil moisture in different landscapes across the world; and in turn the variability may affect crop production. Non-flood areas in the Namibian Kwalala Landscape of Zambezi (NKLOZ) region are generally relegated to second place, as somewhat marginal for the successful production of major crops such as maize (Zea mays L.). Even when flood water has receded, non-flooded areas which get affected during floods, are still avoided for crop production. This is because residual moisture following the rainy season, is suspected to fall far short of the longer growing duration of maize, to the extent that farmers are too apprehensive to grow maize in such areas. The objective of this study was to determine the effect of seasonal rainfall on spatial and temporal variability of soil moisture within the Namibian Kwalala Landscape of Zambezi (NKLOZ) ecology, and the extent to which soil moisture status and soil temperature patterns (STEPs) characterise soil type (STP) productive potential. Three sensors were setup up at 20, 40 and 60 cm landscape of the NKLOZ, after digging a one-metre trench at each site. Soil moisture and temperature data were retrieved and monitored using Decagon DataTrac 3 software. ANOVA multiple regressions were used to analyse the effects of soil depth, rainfall, and soil temperature on soil moisture. Seasonal rainfall in the NKLOZ during the growing period between October and April (2012-2015) significantly (P < 0.05) and positively affected soil moisture, both in time and space, in recharging soil moisture to sufficiently meet maize crop water requirements in the region. Although it appeared like high amounts of soil moisture sufficiency were as a result of the events of seasonal rainfall received during the growing period, anything received between mid-January and Mid-March was still below the historical minimum and maximum decadal; and in any case late for early planted maize crop. Average soil moisture data indicated for loamy soil (8.30), sandy loam (14.30) and sand at the respective sites suggested a large rainfall season-soil texture interaction. Such an interaction should inform the prudence of production of maize from the point of view of a smart or robust crop system growing planning and management.
 Key words: Decagon sensors, residual moisture, Zea mays

Flood mapping using Sentinel-1 SAR Imagery: Case study of the November 2017 flood in Penang

The Sentinel-1 SAR image by the Europe Space Agency (ESA) in the Copernicus Programme is an open source data which offers good data to develop flood inundation mapping. The flood inundation mapping is essential information for local authority personals or researchers to develop flood inventory map. The objective of this study is to develop a flood inundation mapping on November 2017 event to assess its use as potential flood inventory mapping data in Penang. The threshold method was carried out using Sentinel-1 image to extract the flood map. This method is pixel value used to separate the grey image into two parts. The flooded and non-flooded areas can be identified by separating the backscatter lower than the threshold value. The results revealed that the flood inundation maps are able to be extracted out from Sentinel-1 images.

Moderate inundation stimulates plant community assembly in the drawdown zone of China\u2019s Three Gorges Reservoir

BackgroundWhile a dam is constructed to adjust and store water resources, it has negative impacts on biodiversity of the corresponding ecosystems. In particular, the dam regulation induces water-level fluctuations (WLFs), resulting in remarkable effects on the riparian vegetation succession of the drawdown zone ecosystem. These riparian plant responses play important roles in the biodiversity conservation. However, in-depth investigative adequate studies are still lacking. The objective of this study was to assess the community assembly under the anti-seasonal WLFs of China’s Three Gorges Reservoir (TGR). To analyze the WLFs’ impacts on plant community, the drawdown zone of the TGR was divided into four sub-zones (zone I, II, III, and IV) according to the inundation periods. The community biomass, height, total coverage, and species diversity in each sub-zone were surveyed. To detect the response of individual plant to the WLFs, dominant plants of Echinochloa crusgalli, Setaria viridis, Bidens pilosa, and Xanthium sibiricum were selected as targeted species to compare the plant’s morphological and physiological traits between non-flooded area and the moderately inundated area.ResultsThe peaks of community biomass (1859.62 ± 663.77 g), total coverage (103.93 ± 11.81%), and diversity indexes were found in zone II that experienced 90 days of inundation. Community height and total coverage were both significantly negatively correlated to the inundated gradients. Generalized linear models and quadratic regression analyses revealed that community biomass, height, and total coverage were strongly related to the inundated gradients, implying that the inundation is the major factor contributing to the variation of the riparian vegetation patterns. The values of morphological traits (plant height and biomass) in the zone II were higher than those in the non-flooded zone, and were significantly positively correlated with physiological traits.ConclusionsCommunity structure, diversity, and functional traits analysis indicated that the drawdown zone referencing to the 90-day inundation was suitable for the plant community establishment. Results on plant functional traits suggest the adaption of riparian plants to the TGR hydrological regime. However, further investigative studies with more plant species are necessary to elucidate their adaptation mechanisms.

Rapid flood inundation mapping by differencing water indices from pre- and post-flood Landsat images

Following flooding disasters, satellite images provide valuable information required for generating flood inundation maps. Multispectral or optical imagery can be used for generating flood maps when the inundated areas are not covered by clouds. We propose a rapid mapping method for identifying inundated areas based on the increase in the water index value between the pre- and post-flood satellite images. Values of the Normalized Difference Water Index (NDWI) and Modified NDWI (MNDWI) will be higher in the post-flood image for flooded areas compared to the pre-flood image. Based on a threshold value, pixels corresponding to the flooded areas can be separated from non-flooded areas. Inundation maps derived from differencing MNDWI values accurately captured the flooded areas. However the output image will be influenced by the choice of the pre-flood image, hence analysts have to avoid selecting pre-flood images acquired in drought or earlier flood years. Also the inundation maps generated using this method have to be overlaid on the post-flood satellite image in order to orient personnel to landscape features. Advantages of the proposed technique are that flood impacted areas can be identified rapidly, and that the pre-existing water bodies can be excluded from the inundation maps. Using pairs of other satellite data, several maps can be generated within a single flood which would enable emergency response agencies to focus on newly flooded areas.

Partial flooding and its effect on the performance of a proton exchange membrane fuel cell

Water management is one of the key issues for efficient and stable operation of proton exchange membrane fuel cells (PEMFCs). Water flooding easily occurs at the elevated operation current density, especially at the downstreaming of the flow channel where the generated water should flow out. Proper water management should meet the needs of adequate membrane hydration and the avoidance of flooding in the catalyst and gas diffusion layers. Flooding will not only lead to performance losses due to the hindered reactant supply, but also the safety issue because of the cell reversal. A partial flooding model is proposed to investigate the effect of the porosity on the performance of a PEMFC. The results show that high temperature is conducive to the suppression of flooding at low relative humidity, and flooding would lead to the deterioration of mass transfer due to the porosity decrease of gas diffusion layer, especially at high current densities. Partial flooding won’t significantly affect the power generation capacity of the fuel cell, but will cause uneven distribution of current density, resulting in an adverse influence on long-term operation. Moreover, the performance would suffer serious degradation with completely flooding. Once the area inside the PEMFC is seriously flooded, the current density in non-flooded area is up to 4.7 times higher than that in the flooded area, and the performance is difficult to recover even if increasing the stoichiometry of reactants. The study illustrates the importance of the water management at the downstreaming of the fuel cell.

Wetland plant litter decomposition occurring during the freeze season under disparate flooded conditions

To investigate the heterogeneity of plant litter decomposition in the freeze and freeze-free seasons and the responses to disparate flooded conditions in seasonally frozen wetlands, in situ simulation experiments of litter decomposition were performed in the Sanjiang Plain, Northeast China. The experiments were conducted using the litter bag method for representative plants, Carex lasiocarpa and Calamagrostis angustifolia, in both non-flooded and flooded areas between November 2011 and November 2013. Heterogeneous effects of the freeze season and its interaction with hydrological regimes on the decomposition of the litter of various species and organs were observed. The litter decomposition occurred during the freeze season and made a significant contribution to the loss throughout the year. The two-year mass-loss of C. lasiocarpa and C. angustifolia and their organs were ordered differently between the freeze season and the freeze-free season. The proportion of litter mass-loss during the freeze season accounting for the whole year in the flooded area were greater than that in the non-flooded area, except for the C. angustifolia root litter. The litter mass-losses of entire C. lasiocarpa and C. angustifolia during the freeze season were greater than those during the freeze-free season in the flooded area, while the pattern was opposite in the non-flooded area. The effect of environmental factors on litter decomposition might override the effects of litter substrate quality. The total N and P of the litter of the entire C. lasiocarpa and entire C. angustifolia increased significantly relative to the initial values after two years and tended to enrich more in the litter under flooded conditions than under non-flooded conditions. The results highlighted the heterogeneous effects of the freeze season and its interaction with hydrological regimes on various species and organs, which would provide management and restoration options for degraded wetlands caused by climate change.

Shifts in characteristics of the plant-soil system associated with flooding and revegetation in the riparian zone of Three Gorges Reservoir, China

The operation of the Three Gorges Reservoir (TGR), the largest hydropower dam in the world, has triggered a dramatic shift in the flooding regimes of sites upstream of the reservoir. Little is known about how disrupted flooding regimes and consequent management approaches might affect the ecological and biogeochemical characteristics of riparian ecosystems. In this study, we evaluated the effects of disruptions to natural flooding regime on basic soil properties, soil nutrient and heavy metal levels, and key characteristics of riparian plant and soil microbial communities. To do this, we used an elevational gradient that encompassed four flooding duration zones (0 (i.e., control), 169, 237, 286 days of flooding per year on average). The disrupted flooding regimes were associated with levels of soil total N and P that were on average 17% and 24% lower, respectively, than those in the non-flooded areas. On the other hand, the concentrations of heavy metals (Hg, Pb, Cu, Zn and Mn) were higher in flood-affected areas than in the non-flooded areas. Increased flooding frequency was also associated with lower plant diversity and species richness relative to non-flooded areas. Thus, disruption of the natural flooding regime had strong and often negative consequences for the ecological and biogeochemical properties of the riparian ecosystems in our study. There was some evidence that riparian plant communities were able to partially recover from prior flooding during a single growing season, even after nine years of repeated flooding, and these recovery trajectories were associated with shifts in soil chemical properties during the same period. However, revegetation efforts had few effects on ecosystem properties or their recovery trajectories following flooding events, suggesting that natural regeneration could be a useful option for the management of these sites. We conclude that the unnatural flooding regimes associated with large scale reservoir development are likely to have profound impacts on the structure and functioning of riparian ecosystems, and these will pose a considerable challenge for environmental management and biodiversity conservation.

Is Leaf Water-Repellency and Cuticle Roughness Linked to Flooding Regimes in Plants of Coastal Wetlands?

Owing to periodic inundation, wetland plants may have adapted to minimize leaf gas exchange impairments. Increasing the leaf cuticle surface roughness might contribute to buffer flooding stress, since it might increase both leaf water repellency (i.e. leaf hydrophobicity) and the presence of gas films. Thus, a higher leaf hydrophobicity, as well as an increased cuticle roughness, can be expected in species subject to continuous water-logging. We tested this hypothesis by: 1) measuring the contact angle in the liquid-solid interface on leaves of 52 plant species from three coastal wetlands with different diversity and flooding regime in Baja California, Mexico, and 2) by performing scanning electron microscopic analyses in the most hydrophilic and hydrophobic species. Contrary to our expectations, the highest values of leaf water repellency were found in species from non-flooded areas adjacent to the wetlands, whereas neutral leaf water repellency values were found in species subject to flooding, as indicated by the contact angle measurements (77 to 100°). The most water repellent species presented a striking layer of wax on top of the leaf cuticles, while the lest water repellent species were mostly glabrous, which suggest that the augmentation of wax covering in the cuticle might be responding to other environmental factors, such as irradiation.

Let the Rich Be Flooded: The Unequal Impact of Hurricane Harvey on Household Debt

Outside of flood hazard zones, households must decide whether to insure or rely on disaster assistance to manage flood risk. We use the quasi-random flooding generated by Hurricane Harvey, which hit Houston in August 2017, to understand the implications of flood losses for households with differing access to insurance and credit. Outside the floodplain, credit-constrained homeowners experience a 20% increase in bankruptcies and a 13% increase in the share of debt in severe delinquency in flooded blocks relative to non-flooded areas. Treatment effects are universally insignificant inside the floodplain, implying that flood insurance mitigates the financial impact of flooding across the credit distribution. Disaster assistance, on the other hand, does not appear to counteract the role of initial inequalities on post-disaster credit outcomes. We find SBA disaster loans and, more surprisingly, FEMA grants to both be regressive in allocation. Our results highlight that averages mask important heterogeneity after disasters, which challenges existing narratives of how effectively Federal disaster programs mitigate the financial burden of natural disasters.

The impact of the 2016 flood event in Anhui Province, China on infectious diarrhea disease: An interrupted time-series study

Climate change may bring more frequent and severe floods which will heighten public health problems, including an increased risk of infectious diarrhea in susceptible populations. Affected by heavy rainfall and an El Niño event, a destructive flood occurred in Anhui province, China on 18th June 2016. This study investigates the impact of this severe flood on infectious diarrhea at both city-level and provincial level, and further to identify modifying factor. We obtained information on infectious diarrheal cases during 2013–2017 from the National Disease Surveillance System. An interrupted time-series design was used to estimate effects of the flood event on diarrhea in 16 cities. Then we applied a meta-analysis to estimate the area-level pooled effects of the flood in both flooded areas and non-flooded areas. Finally, a meta-regression was applied to determine whether proximity to flood was a predictor of city-level risks. Stratified analyses by gender and age group were also conducted for flooded areas. A significant increase in infectious diarrhea risk (RR = 1.11, 95% CI: 1.01, 1.23) after the flood event was found in flooded area with variation in risks across cities, while there was no increase in non-flooded areas. Diarrheal risks post-flood was progressively higher in cities with greater proximity to the Yangtze River. Children aged 5–14 were at highest risk of diarrhea post-flood in the flooded areas. Our study provides strong evidence that the 2016 severe flood significantly increased infectious diarrheal risk in exposed populations. Local public health agencies are advised to develop intervention programs to prevent and control infectious diarrhea risk when a major flood occurs, especially in areas close to water bodies and among vulnerable populations.

Passive Microwave Remote Sensing of Flood in Tropical Regions

Space based flood monitoring can provide a systematic and timely solution to the problem of flood mapping. This paper presents a way to detect as well as monitor flood by using passive microwave remote sensing (MRS). The method is based on the use of brightness temperature taken from Passive MRS Satellite. A case study from October 2012 to September 2013 on Dhemaji district of Assam, India shows that the brightness temperature (T b ) ratios of measured and calibrated places for the same days can be used for discriminating the flooded and non-flooded areas efficiently. In comparison to conventional methods used in the same field, the proposed method is more accurate, which uses a threshold value of the T b ratio for detection of flooding and non-flooding conditions. Keywords: Microwave Remote Sensing, Flood detection, Brightness Temperature, SSM/I

Agroecosystem resilience in response to extreme winter flooding

Evidence suggests that climate change is increasing the frequency of extreme weather events (e.g. excessive rainfall, heat, wind). The winter of 2013-14 saw exceptional levels of rainfall across the UK leading to extreme and prolonged flooding (up to 3 months with floodwater depths up to 3 m) in several low-lying agricultural areas (e.g. Somerset Levels, Thames Valley). The impact of extreme flooding and the speed of ecosystem recovery at the field-scale, however, remain poorly understood. The main objectives of this study were therefore to: (1) assess the effect of this extreme winter flooding event on a range of soil physical, chemical and biological quality indicators at 15 flood-affected sites (arable and grassland), (2) determine if these changes in soil health were reversible in the short term (< 1 year), and (3) to evaluate the effectiveness of different mechanical interventions (sward-lifting, subsoiling, slot-seeding and aerating) to accelerate the amelioration of the damage caused by winter flooding at 2 of the 15 sites. Once the floodwater had receded (April 2014), we found that several of the measured soil quality indicators were negatively affected in the flooded areas in comparison with non-flooded areas. This included a decrease in soil bulk density (by 19%), soil pH (by 0.4 units), and available P (by up to 42%). Flooding increased soil microbial biomass (60%), induced a shift in soil microbial community structure and reduced earthworm numbers. After 8 months of recovery, only soil pH remained significantly reduced (by 0.3 units) in the flooded areas in comparison to the unflooded areas. Flooding had a negative impact on the overlying vegetation at the arable sites (biomass production was reduced by between 19 and 34%) but had no major impact at the grassland sites in the long-term. In the flood amelioration experiment, the subsoiled plots produced grass with a higher nutrient content (e.g. N - up to 35%, Ca - up to 19% and Mg - up to 58%). However, the four different interventions appeared to have little positive impact on most of the soil quality indicators measured. In conclusion, extreme winter flooding was found to induce short-term alterations in key soil quality indicators and to destroy winter crops, although these effects did not persist in the longer term. Our results therefore indicate that the temperate agroecosystems evaluated here were highly resilient to winter flood stress and that recovery to a pre-flood state could be achieved within 1 year. Improved management strategies are still needed to speed up the rate of recovery after flood events to facilitate a faster return to agricultural production.

Chilopoda and Diplopoda of semi natural flooded meadows in Matsalu, Estonia

In Matsalu National Park a flood is a natural disturbance which shapes ecosystems and communities. The impact of human activities (e.g. extensive mowing once a year or low stress grazing) on the habitat in this area is low. The disturbances are caused by natural conditions such as melting snow, precipitation and brackish sea water and the presence of flood is supported by flat relief. The aim of the current study was to describe the Chilopoda and Diplopoda assemblages of semi natural meadows and to find out the effect of habitat conditions on these invertebrates. On the 12 studied meadows we sampled and analysed soil invertebrates by using pitfall traps in the non-flooded and flooded areas of meadows. The individuals of 10 Chilopoda species and 15 Diplopoda species, which assemblages were more abundant and diverse in the non-flooded areas of meadows with trees and bushes nearby, were collected on semi natural meadows in Matsalu. Only a few species were represented in abundance on studied meadows including Leptoiulus proximus, L. cibdellus, Julus terrestris, J. scanicus. The species Pachymerium ferrugineum, Schendyla nemorensis, Julus terrestris, J. scanicus, Leptoiulus cibdellus, Xestoiulus laeticollis were also found in the areas flooded with brackish water. The activity density and species richness of Chilopoda and Diplopoda were significantly lower in the flooded areas of the meadow after flood water withdrawal compared to the non-flooded areas of the same meadows.