•The abundance of springtails is low on meadows with long-term flood.•In habitats with shorter flood the effect of floods on springtails is rather positive.•Brackish flood water negatively influences ...springtail communities in meadow soil.•Only species tolerant to unstable habitat conditions are abundant in flooded areas.
The brackish conditions of the Baltic Sea create special habitats in coastal meadow soils surrounding Matsalu Bay. The floodplains of the Kasari River are periodically flooded by fresh water. In the eastern part of Matsalu Bay and in the delta of the river, brackish and fresh water can be mixed due to strong winds from the west or due to exceptionally large amounts of fresh water flowing from the river in the spring. The aim of this study was to find out how flood and habitat soil salinity influence the abundance and diversity of springtail communities on flooded meadows. The studied meadows were grouped to four types by distance of study sites from the open sea and by soil electroconductivity: fresh floodplain, wet floodplain, transitional and coastal grasslands. Springtail communities on temporarily flooded meadows along Matsalu Bay and the Kasari River consist of 20 − 30 species per meadow type, species Metaphorura affinis, Willemia anophthalma, Brachystomella parvula, Folsomia quadrioculata were abundant in soil of all types of meadows. Our results confirmed that flooding is an important factor in shaping soil communities. Long-term flood had strong negative effect on springtail communities’ abundance and diversity. However, there was no such negative effect of flood on meadows with shorter flooding period, for several species the flood was positive factor increasing the abundance. Flooding brackish sea water is the reason for higher electroconductivity of meadow soils negatively influencing the diversity of springtail communities. The abundance of several species was the highest in soil of coastal grasslands (Agrenia bidenticulata, Folsomia sexoculata, Podura aquatica, Sminthurides schoetti) despite the higher salinity of soil. The impact of flood duration on the composition of communities by life forms seemed to be less important than the impact of soil salinity, saline soil was not a suitable habitat for euedaphic springtails.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Duration is a key characteristic of floods influencing the design of protection infrastructures for prevention, deployment of rescue resources during the emergency, and repartition of damage costs in ...the aftermath. The latter financial aspect mainly relies on the insurance industry and allows the transfer of damage costs from the public sector to the private capital market. In this context, the cost of catastrophes affecting a large amount of insured properties is partly or totally transferred from insurance companies to reinsurance companies by contracts that define the portion of transferred costs according to the temporal extent of the flood events synthesized in the so-called hours clause. However, hours clauses imply standard flood event durations, such as 168 h (1 week), regardless of the hydrological properties characterizing different areas. In this study, we firstly perform a synoptic-scale exploratory analysis to investigate the duration and magnitude of large flood events that occurred around the world and in Europe between 1985 and 2016, and then we present a data-driven procedure devised to compute flood duration by tracking flood peaks along a river network. The exploratory analysis highlights the link of flood duration and magnitude with flood generation mechanism, thus allowing the identification of regions that are more or less prone to long-lasting events exceeding the standard hours clauses. The flood tracking procedure is applied to seven of the largest river basins in Central and Eastern Europe (Danube, Rhine, Elbe, Weser, Rhone, Loire, and Garonne). It correctly identifies major flood events and enables the definition of the probability distribution of the flood propagation time and its sampling uncertainty. Overall, we provide information and analysis tools readily applicable to improve reinsurance practices with respect to spatiotemporal extent of flooding hazard.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The occurrence and distribution of aquatic macrophytes within a wetland depends on the hydrological requirements of each species and the hydrological conditions. The aims of this study were to: (1) ...determine relationships between germination of
Eleocharis acuta
and
Eleocharis sphacelata
and hydrological regime, (2) determine the buoyancy of the seeds of
E. acuta
and
E. sphacelata
and hence their ability to disperse by hydrochory and (3) determine whether
E. acuta
and
E. sphacelata
exhibit dormancy. The seeds of
E. acuta
and
E. sphacelata
both germinated best on soil-soaked and when inundated for 80 days (to a depth of 5 cm). No seeds of either species germinated under rainfall conditions. Viability testing following the experiment showed that some seeds of both species remained ungerminated and viable following soaking, inundation and rainfall conditions for 90 days, demonstrating that
E. acuta
and
E. sphacelata
exhibit dormancy. At least 50% of
E. acuta
seeds floated for 32 days, while 50% of
E. sphacelata
seeds remained floating for at least 39 days. These germination and dispersal characteristics define where and when these
Eleocharis
species establish related to temporal and spatial hydrological variability.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
24.
Stochastic analysis of flood series Vukmirovic, Vojislav; Vukmirovic, Nenad
Hydrological sciences journal,
08/2017, Volume:
62, Issue:
11
Journal Article
Peer reviewed
A stochastic model based on the renewal process was developed and used to analyse the characteristics of floods: the volume exceedence, the duration of the flood and the maximum annual flow. The ...model contains a method for determination of total annual volume exceedence and total annual duration of floods, as well as a method for calculation of maximum annual exceedence, maximum flood duration and maximum flow. The subset of the flood occurrence number in a given time interval is common for all analysed phenomena (volume exceedence, flood duration, maximum flow). The subset of given exceedences is common for total annual volume exceedence, as well as for maximum annual volume exceedence. The same holds for durations of individual floods. The model was then applied to analyse the floods on the Drina River at the Paunci hydrological station and on the Danube River at the Bezdan station.
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Gated storm surge barriers are being studied by the United States Army Corps of Engineers (USACE) for coastal storm risk management for the New York City metropolitan area. Surge barrier gates are ...only closed when storm tides exceeding a specific “trigger” water level might occur in a storm. Gate closure frequency and duration both strongly influence the physical and environmental effects on enclosed estuaries. In this paper, we use historical observations to represent future storm tide hazard, and we superimpose local relative sea-level rise (SLR) to study the potential future changes to closure frequency and duration. We account for the effects of forecast uncertainty on closures, using a relationship between past storm surge and forecast uncertainty from an operational ensemble forecast system. A concern during a storm surge is that closed gates will trap river streamflow and could cause a new problem with trapped river water flooding. Similarly, we evaluate this possibility using historical data to represent river flood hazard, complemented by hydrodynamic model simulations to capture how waters rise when a hypothetical barrier is closed. The results show that SLR causes an exponential increase of the gate closure frequency, a lengthening of the closure duration, and a rising probability of trapped river water flooding. The USACE has proposed to prevent these SLR-driven increases by periodically raising the trigger water level (e.g., to match a prescribed storm return period). However, this alternative management approach for dealing with SLR requires waterfront seawalls to be raised at a high, and ongoing, additional future expense. For seawalls, costs and benefits will likely need to be weighed on a neighborhood-by-neighborhood basis, and in some cases retreat or other non-structural options may be preferable.
Recently, spatial organization in salt marshes was shown to contain vital information on system resilience. However, in salt marshes, it remains poorly understood what shaping processes regulate ...spatial patterns in soil or vegetation properties that can be detected in the surface reflectance signal. In this case study we compared the effect on surface reflectance of four major shaping processes: Flooding duration, wave forcing, competition, and creek formation. We applied the ProSail model to a pioneering salt marsh species (Spartina anglica) to identify through which vegetation and soil properties these processes affected reflectance, and used in situ reflectance data at the leaf and canopy scale and satellite data on the canopy scale to identify the spatial patterns in the biophysical characteristics of this salt marsh pioneer in spring. Our results suggest that the spatial patterns in the pioneer zone of the studied salt marsh are mainly caused by the effect of flood duration. Flood duration explained over three times as much of the variation in canopy properties as wave forcing, competition, or creek influence. It particularly affects spatial patterns through canopy properties, especially the leaf area index, while leaf characteristics appear to have a relatively minor effect on reflectance.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Hydrodynamic flow modeling is carried out using a coupled 1D and 2D hydrodynamic flow model in northern India where an industrial plant is proposed. Two flooding scenarios, one considering the ...flooding source at regional/catchment level and another considering all flooding sources at local level have been simulated. For simulating flooding scenario due to flooding of the upstream catchment, the probable maximum flood (PMF) in the main river is routed and its flooding impact at the plant site is studied, while at the local level flooding, in addition to PMF in the main river, the probable maximum precipitation at the plant site and breaches in the canals near the plant site have been considered. The flood extent, depth, level, duration and maximum flow velocity have been computed. Three parameters namely the flood depth, cross product of flood depth and velocity and flood duration have been used for assessing the flood hazard, and a flood hazard classification scheme has been proposed. Flood hazard assessment for flooding due to upstream catchment and study on local scale facilitates determination of plinth level for the plant site and helps in identifying the flood protection measures.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Wetland hydroperiod consists of different components, including frequency, duration and depth. A significant proportion of the seasonally flood-pulsed Okavango Delta is inundated for part of each ...year. Variation in hydroperiod, driven by the interaction of climate and ecological factors, results in a mosaic of vegetation communities. These communities are highly dynamic over temporal and spatial scales. This study aimed to identify quantitative relationships between hydroperiod components and floodplain vegetation, to better understand the potential effects of hydrological change. A stratified random sample of 30 floodplains was surveyed for species composition and abundance. Hydroperiod components for sample quadrats were estimated from remote sensing and field measurement. Ordination demonstrated strong correlations between species composition and flood frequency, duration, years-since-last-flood and depth. Eight statistically discrete vegetation communities were derived from cluster analysis. Generalized linear models of species distributions along hydrological gradients were used to derive frequency and duration optima. Means of these parameters differed significantly between communities. Increasing hydroperiod corresponded with a progression from grasslands through sedge-dominated to aquatic communities. Species in infrequently flooded areas indicated disturbance and a succession trend towards open woodland. In the sedgelands, average depth was the strongest correlate, while in grasslands and aquatic communities, this was duration.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•We developed a framework to assess and map flood-regulation capacity (FRC).•Natural landscape features and technological features both contribute to FRC.•We used long-term hydrologic data to ...characterize floods and landscape processes.•Analysis of watershed-scale FRC may inform flood-control strategies.
Flood regulation is a widely valued and studied service provided by watersheds. Flood regulation benefits people directly by decreasing the socio-economic costs of flooding and indirectly by its positive impacts on cultural (e.g., fishing) and provisioning (e.g., water supply) ecosystem services. Like other regulating ecosystem services (e.g., pollination, water purification), flood regulation is often enhanced or replaced by technology, but the relative efficacy of natural versus technological features in controlling floods has scarcely been examined. In an effort to assess flood regulation capacity for selected urban watersheds in the southeastern United States, we: (1) used long-term flood records to assess relative influence of technological and biophysical indicators on flood magnitude and duration, (2) compared the widely used runoff curve number (RCN) approach for assessing the biophysical capacity to regulate floods to an alternative approach that acknowledges land cover and soil properties separately, and (3) mapped technological and biophysical flood regulation capacities based on indicator importance-values derived for flood magnitude and duration. We found that watersheds with high biophysical (via the alternative approach) and technological capacities lengthened the duration and lowered the peak of floods. We found the RCN approach yielded results opposite that expected, possibly because it confounds soil and land cover processes, particularly in urban landscapes, while our alternative approach coherently separates these processes. Mapping biophysical (via the alternative approach) and technological capacities revealed great differences among watersheds. Our study improves on previous mapping of flood regulation by (1) incorporating technological capacity, (2) providing high spatial resolution (i.e., 10-m pixel) maps of watershed capacities, and (3) deriving importance-values for selected landscape indicators. By accounting for technology that enhances or replaces natural flood regulation, our approach enables watershed managers to make more informed choices in their flood-control investments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
AbstractMost flood risk studies quantify flood likelihood and damage as functions of depth. The length of time that a flood remains above a stage (duration) is also necessary to quantify ...infrastructure vulnerability. The proposed approach adds a second dimension, time, into flood risk studies by developing a joint distribution of flood stage and event duration. Bivariate flood frequency model metrics are developed; the metrics are illustrated using data from four gauged sites, two riverine and two tidal. It is concluded that a general joint distribution model is applicable to both riverine and tidal sites. A minimum time between events (interevent time) determines the assignment of sequential periods to a single event or multiple events; this measure is shown to affect the statistics of the tidal sites, but not the riverine sites. The flood stage-duration-frequency curves developed in this study demonstrate a new approach that allows stakeholders to consider the coupling between depth and duration, and thereby develop preparedness and response plans that address temporal aspects such as time out of service in addition to depth-dependent damages.
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