Changes in flood regimes, floodwater quality, and macrophyte types may affect sediment characteristics post-flooding. However, few studies have attempted to unravel their complex influences in ...floodplain wetlands. From 2011 to 2020, the physical and chemical properties of surface layer sediment pre- and post-flooding was investigated through field surveys in the Dongting Lake wetland. Results indicated that the pre-flooding soil total phosphorus (TP) and total nitrogen (TN) exhibited an increasing trend during 2011–2020. Soil TP increased post-flooding relative to that pre-flooding. The changes in TN, sediment organic matter (SOM), sediment moisture content (SMC), and sediment bulk density (SBD) fluctuated over the years. The best-fitting multi-regression model demonstrated that the changes in sediment variables post-flooding showed a parabolic trajectory along the inundation duration (ID), except for SMC. Changes in soil properties post-flooding were negatively correlated with ID for sediment with a low IDs (<148 days). Meanwhile, changes in soil properties post flooding were positively correlated with ID for sediment with a high IDs (>193 days). Changes in SBD and SOM post-flooding were positively influenced by the TP content in the floodwater. These findings indicate that changes in the flooding regime, and water quality generated by anthropogenic disturbances such as the Three Gorges Dam significantly affect sediment properties, and subsequently influence the ecological functions of the Dongting Lake wetland.
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•Pre-flooding sediment TN and TP content exhibited an increasing trend.•Soil TP content generally increased post-flooding relative to pre-flooding.•Sediment properties changed parabolically along the inundation duration gradient.•High TN content in flood water increased sediment TN content post flooding.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Coastal Louisiana is experiencing extremely high rates of wetland loss, particularly within the Mississippi River Deltaic Plain. Although multiple stressors contribute to this loss, one major driver ...is decreased wetland elevation stemming from disconnection of recurrent sediment rich influxes of Mississippi River floodwater. The decrease in sediment delivery, in conjunction with natural subsidence processes, reduce marsh elevations and increase flooding stress on vegetation, leading to marsh collapse. River sediment diversions are large-scale restoration techniques intended to rehabilitate Louisiana's degraded coastal wetlands by mimicking historic crevasse splays, thereby stimulating land building and vegetation growth. However, such large-scale restoration techniques require an appropriate knowledge base of vegetation and soil biogeochemical responses to altered environmental conditions. In this research, monospecific sods of three foundational marsh species (Spartina patens, Spartina alterniflora, Typha latifolia) were exposed to inundation depth (20 and 40 cm), duration (8 and 16 weeks), and salinity (0 and 5 psu) treatments consistent with a range of anticipated sediment diversion scenarios in a mesocosm setting. Additionally, sods were monitored through week 20 after being removed from their experimental conditions. Both Spartina alterniflora and Typha latifolia displayed relatively consistent increases in stem densities over time across inundation depth-duration treatments, whereas Spartina patens displayed a sharp decline in stem densities at 40 cm flooding depths. Additionally, both Spartina alterniflora and Spartina patens had the least observed amount of total aboveground biomass at 40 cm flooding depths. Spartina patens sods displayed a significant loss in surface elevation with increased flooding stress through study week 20, whereas Typha latifolia demonstrated a significant gain in surface elevation. These results suggest that restoration projects increasing inundation within the limits of the depths employed herein and the anticipated duration of river diversion induced inundation are unlikely to negatively impact the aboveground growth responses of Spartina alterniflora and Typha latifolia, but could reduce stem densities and aboveground biomass of Spartina patens.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Due to the penetration capacity of synthetic aperture radar (SAR) data through clouds and hazy atmospheric circumstances like fog, smog, light rain, mist etc., it has ability to continuous ...observation of flood events for producing accurate, rapid and cost effective flood mapping. A study using time series RADARSAT SAR images in flood water detection, monitoring of spatial extent and propagation of flood inundation were described and analysed in this paper. The SAR images were first calibrated, geometrically corrected and filtered. Afterward, threshold method was applied to extract the inundated areas from the SAR images. In threshold method, density slicing technique was used to separate the open water and non-water (land) areas from the images. Later, to delineate the actual flooded area, permanent water bodies (e.g. river, lake, ponds etc.) were subtracted from the open water. Flood maps were super-imposed and analysed to find out the nature of spatial extent, duration of flood and to show how flooding spread through time. This study illustrates that the SAR data along with GIS can be used effectively for flood water mapping, monitoring and analysing the propagation of flood water in a flood prone area. Therefore, the findings of this study will help to take initiative to reduce the flood hazard impact and increase the flexibility in the process of flood management.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of unsteady currents on scour at piers was investigated. The tests were run for nine pier shapes, three installation positions along a 180° bend, four flood durations, and four ratios of ...rising limb to flood duration for the 100-minute flood durations. Overall, including seven tests performed in the bend without piers, 196 tests were performed. The flow rapidity ranged from the movement threshold to live bed situations. The results indicated that the deepest scour-hole in front of the piers with different shapes was a function of flood duration and the ratio of ascending branch to descending branch had little effect on the final maximum scour-hole depth around the pier. The scour-hole volume is affected by the nose and the cross-sectional shape of the pier. For the rectangular pier, the scour-hole volume is greater than that of the other piers. The average shape coefficient was calculated.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
•A novel framework is developed for integrated hydrologic validation of satellites.•Assessment focuses on flood characteristics in favor of bulk metrics.•The effects of IMERG resolution are seen on ...flood peak discharge.•Basin size is also found to play a role in over or underestimation of peak discharge.•IMERG simulated floods events start earlier and end later than the MRMS benchmark.
In recent years, a great amount of research has been done towards evaluating precipitation data generated by satellites, but less has focused on how these estimates and their uncertainties manifest further into the water cycle. In this study, ten years of satellite-based and ground-based radar data are used as forcings for a distributed hydrologic model across the Continental United States. They are compared using a methodology designed to assess the flood signals and characteristics generated by the model. By focusing on how well the model reproduces flood characteristics rather than fits traditional bulk statistics, this research provides robust insights into satellite precipitation deficiencies. It is found that satellite data has greater success at resolving lower magnitude flood events while tending to generate floods of longer durations. Additionally, flood managers should note that satellites tend to generate floods that characteristically both begin earlier and end later than the ground radar reference. Subsequent research is recommended into other satellite data products in order to better understand these discrepancies and mitigate or plan for them in the future.
In recent years, satellites have been increasingly used to provide valuable insights on rainfall across the globe, especially in locations where radars are unable to be installed on the ground. By nature, however, the rainfall data provided by satellites has uncertainties. Large amounts of research has gone into the difference in accuracy between satellite radar and ground references, but less has focused on how these differences impact flood simulations, respectively. In this study it was found that the rainfall data from satellites tends to predict floods that are more severe (have higher magnitudes), last longer (have longer durations), and have different timings (start earlier and end later) than the reference. It is also found that satellites struggle with predictions involving extreme rainfall values. Further research is suggested to better understand these issues, as well as compare against other forms of satellite rainfall data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Design flood values give estimates of flood magnitude within a given return period and are essential to making adaptive decisions around land use planning, infrastructure design, and disaster ...mitigation. Many hydrologic applications where flood retention is important, e.g. floodplain management and reservoir design, need design flood values for different durations. Flood–Duration–Frequency (QDF) models extend the standard statistical flood frequency analysis framework to multiple flood durations and are analogous to intensity–duration–frequency models for precipitation. Implementations of QDF models commonly assume simple scaling, where only the magnitude of the index flood is assumed to change with duration, despite empirical analyses showing a more complex dependence structure. We propose a multiscaling extension to existing QDF models where the magnitude of the index flood and the slope of the growth curve may scale independently with duration. In an application to 12 locations in Norway, we assess how three different QDF models capture relationships between floods of different duration. Incorporating duration dependency independently in both the index flood and the growth curve (extended QDF model) improves modeling of both short-duration events and events with long return periods. This model extension further expands the models’ ability to simultaneously model a wide range of durations. As measured by the integrated quadratic distance, the extended QDF model performs better than the original QDF model in 83% of the out of sample subdaily durations studied. Additionally, we find that the choice of durations used to fit QDF models is a highly influential aspect of the modeling process.
•Flood–Duration–Frequency (QDF) models produce flood statistics at multiple durations.•We extend QDF models so that different quantiles can have different slopes.•This improves estimates and allows for a wider range of durations to be modeled.•Additionally, we introduce a Bayesian framework for QDF estimation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this article, we propose an integrated direct and indirect flood risk model for small‐ and large‐scale flood events, allowing for dynamic modeling of total economic losses from a flood event to a ...full economic recovery. A novel approach is taken that translates direct losses of both capital and labor into production losses using the Cobb‐Douglas production function, aiming at improved consistency in loss accounting. The recovery of the economy is modeled using a hybrid input‐output model and applied to the port region of Rotterdam, using six different flood events (1/10 up to 1/10,000). This procedure allows gaining a better insight regarding the consequences of both high‐ and low‐probability floods. The results show that in terms of expected annual damage, direct losses remain more substantial relative to the indirect losses (approximately 50% larger), but for low‐probability events the indirect losses outweigh the direct losses. Furthermore, we explored parameter uncertainty using a global sensitivity analysis, and varied critical assumptions in the modeling framework related to, among others, flood duration and labor recovery, using a scenario approach. Our findings have two important implications for disaster modelers and practitioners. First, high‐probability events are qualitatively different from low‐probability events in terms of the scale of damages and full recovery period. Second, there are substantial differences in parameter influence between high‐probability and low‐probability flood modeling. These findings suggest that a detailed approach is required when assessing the flood risk for a specific region.
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BFBNIB, FSPLJ, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The hedonic pricing model (HPM) has been used to identify the values of residential property due to flood impact. Most of the previous studies had been conducted using flood frequency and flood depth ...to measure flood variables rather than flood duration. The hedonic pricing study presented here investigated the effect of flood duration on residential property value in Peninsular Malaysia. We measured the housing attributes involving location, structural, and neighborhood attributes. We also developed the interaction variable between flood and structural attributes to determine whether the effect of flood duration on residential property value differs across house age, size of land area, and number of bedroom. The results suggest that the sale price of residential property is significantly decreased by 0.015 percent due to flood.
•A first global modelling study of ENSO’s influence on flood duration and frequency.•We show strong influence of ENSO on simulated basin-scale flood duration and frequency.•Influence of ENSO found to ...be larger on flood duration than on flood frequency.•Flood impact assessments should attempt to include information on flood duration.
Floods are one of the most serious forms of natural hazards in terms of the damages they cause. In 2012 alone, flood damages exceeded $19 billion. A large proportion of the damages from several recent major flood disasters, such as those in South India and South Carolina (2015), England and Wales (2014), the Mississippi (2012), Thailand (2011), Queensland (Australia) (2010–2011), and Pakistan (2010), were related to the long duration of those flood events. However, most flood risk studies to date do not account for flood duration. In this paper, we provide the first global modelling exercise to assess the link between interannual climate variability and flood duration and frequency. Specifically, we examine relationships between simulated flood events and El Niño Southern Oscillation (ENSO). Our results show that the duration of flooding appears to be more sensitive to ENSO than is the case for flood frequency. At the globally aggregated scale, we found floods to be significantly longer during both El Niño and La Niña years, compared to neutral years. At the scale of individual river basins, we found strong correlations between ENSO and both flood frequency and duration for a large number of basins, with generally stronger correlations for flood duration than for flood frequency. Future research on flood impacts should attempt to incorporate more information on flood durations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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