Inundation Events Research Articles

Factors Affecting Nest Success of Colonial Nesting Waterbirds in Southwest Louisiana

Subsidence and accelerated sea level rise impact nesting area availability and flood probabilities of breeding islands for colonial nesting waterbirds. In 2017 and 2018, we monitored 855 nests of four species of colonial nesting waterbirds on Rabbit Island, LA, to determine factors affecting nest and chick success. Based on logistic exposure models of nests, tricolored herons had the greatest likelihood of survival to hatch (mean (95% confidence interval)) (77% (65.9–83.1%)), followed by brown pelicans (70% (59.9–98.5%)), roseate spoonbills (70% (38.9–83.8%)), and Forster’s terns (12% (10.7–12.2%)). Likelihood of survival to fledge was highest for tricolored herons (32% (12.8–40.7%)), followed by brown pelicans (28% (19.5–28.6%)), roseate spoonbills (47% (43.7–53.3%)), and Forster’s terns (0% (0.005–0.01%)). Nesting strategy and nest timing impacted survival rate; however, the effect depended on timing of inundation events as the timing of inundation events varied across years. Flooding was the primary cause of nest failure for most species. In 2003–2012, rapid expansion in brown pelican colony numbers and significant chick production occurred at Rabbit Island, but hydrologic records indicate no island inundation occurred during the breeding season from the beginning of the hydrologic record (2006) through 2011. Thus, our results contrast with those of previous studies conducted under different hydrologic conditions and demonstrate the challenges of short-term studies informing coastal restoration in a system that is influenced by multi-year to multi-decadal climatic cycles.

Machine learning methods applied to sea level predictions in the upper part of a tidal estuary

Sea levels variations in the upper part of estuary are traditionally approached by relying on refined numerical simulations with high computational cost. As an alternative efficient and rapid solution, we assessed here the performances of two types of machine learning algorithms: (i) multiple regression methods based on linear and polynomial regression functions, and (ii) an artificial neural network, the multilayer perceptron. These algorithms were applied to three-year observations of sea levels maxima during high tides in the city of Landerneau, in the upper part of the Elorn estuary (western Brittany, France). Four input variables were considered in relation to tidal and coastal surge effects on sea level: the French tidal coefficient, the atmospheric pressure, the wind velocity and the river discharge. Whereas a part of these input variables derived from large-scale models with coarse spatial resolutions, the different algorithms showed good performances in this local environment, thus being able to capture sea level temporal variations at semi-diurnal and spring-neap time scales. Predictions improved furthermore the assessment of inundation events based so far on the exploitation of observations or numerical simulations in the downstream part of the estuary. Results obtained exhibited finally the weak influences of wind and river discharges on inundation events.

Pedocomplex buried under the Cabin of Peter the Great in St. Petersburg (1703): Genesis, properties and paleoenvironmental inferences

A study was conducted on the buried soils identified at the base of the foundation of the Cabin of Peter the Great in Saint Petersburg, Russia, to help trace the Late Holocene landscape evolution in the lower reaches of the Neva River. The Cabin is a small wooden house, which was the first residence of Peter the Great in a newly emerged Saint-Petersburg. The house was built of pine logs on the Neva River's right bank. The time of its construction is now regarded as the city's founding date (1703). The pedocomplex with two buried soils has not been truncated and retains a record of the depositional environment, pedogenesis, vegetation history, and human activity before the construction of the city of Saint Petersburg. This pedocomplex was studied using various field and laboratory methods including soil morphology at macro-, meso-, and microlevels, and a full set of microbiomorphic analyses (diatoms, pollen, spores, phytoliths, plant detritus, and amorphous organic matter) supported by radiocarbon dating. The sediment sequence was formed in a contrasting depositional environment. The microbiomorphic studies indicated that the initial substrate was formed in aquatic environments. The analysis of diatoms suggested that these sediments were accumulated as a result of the River Neva breakthrough from Lake Ladoga to the Gulf of Finland ca 3500 yrs BP, which provided additional evidence for the River Neva formation. Soil analyses revealed two inundation events, with the earlier flood related to the termination of the Lake Ladoga transgression (LT) and the breakthrough of the Neva River, whereas the latter flood was likely to be connected with an increase of the fluvial activity. Those two inundation events were followed by two stages of pedogenesis. Both soils indicated the hiatus in sedimentation and were represented by Subquatic Umbric Gleysols that were the most widespread indigenous soils in the XVII century. The pollen data suggest that human impact started at ca 800 yrs BP and eventually resulted in the deforestation and the initial agricultural exploration of the study area. Saint Petersburg is the only large city in Russia that could be at risk from flooding if the sea level rises due to continuing global warming. Our research shows that the city's historical center was twice subjected to flooding in the Late Holocene, even without rises in the sea level. Therefore, the detailed analysis of the environmental dynamics within the Lower Neva area and the assessment of its possible consequences for the city are of great importance.

Analyzing Inundation Impacts on Transportation Network - The Case Study of Vadodara City

Inundation and related problems have become more uncontrollable all over the world leading to unexpected deaths, severe damage to infrastructure, and epidemics like conditions every year. A great number of cities in India have reported a series of heavy hazardous precipitation events during past few years. The immediate effects observed of floods specifically in urban areas are on the transportation network leading to its disruption. Most of the studies on transportation susceptibility including immediate and shortly after inundation events consider topographic properties along with supply and demand side of transportation system to access the disruption caused. In response to such events, this study aims to provide framework to access the susceptibility to urban road network due to inundation events. An integrated framework between meteorological information, land use functions, and hydrodynamic model simulated in HEC-RAS with rainfall event with 1-in-100 year is used for the analysis of the impacts being generated on the transportation infrastructure by such event. A critical map and index is developed to identify affected road length susceptible to flood. It has been observed that more than 40 percent of road length across the network has been affected by such unpredictable events. Also, there is a significant decrease in average speed of movement as compared to average normal speed observed on the normal days.

Simple modelling for a large-scale assessment of total phosphorus retention in the floodplains of large rivers

Floodplains provide a multitude of ecosystem functions and services with water purification being one of them. For this study we modelled the retention of total phosphorous (TP) in the floodplains of the river Rhine and the river Elbe, looking at sediment deposition as the main process responsible for removing TP from rivers during inundation events. We applied two different approaches: a proxy-based approach (PBA) and a one-dimensional model based approach (MBA). We used both to calculate the yearly TP retention and compared it with the annual TP load in the rivers. Compared to the transported river load the Elbe floodplains investigated retained approx. 4.9% TP resp. 1.4% (PBA vs. MBA) while in the floodplains of the river Rhine about 1.8% vs. 0.3% TP was retained. We found that the greatest difficulty in quantifying TP retention in floodplains is due to the lack of spatial detail on the hydrological connectivity between rivers and their adjacent floodplains and that a sound validation of the results is absolutely necessary. Long-term monitoring data for floodplains, especially on hydrological connectivity, are of crucial importance in this respect.

Impact of flood inundation and water management on water and salt balance of the polders and islands in the Ganges delta

Inundation by sea water in coastal areas can devastate cropping; recovery from the impacts can be slow. We used a water and salt balance model of polders to investigate the impacts of and recovery from flood inundation by sea water. We applied the model to three polders in the Ganges delta: Amtali, with high rainfall and low salinity; Dacope with intermediate rainfall and salinity; and Gosaba, with lower rainfall and higher salinity. Dacope and Gosaba were inundated a few years prior to our study, and the model calibration is pertinent to the recovery period. The calculated evapotranspiration from the polder (indicating crop growth) was dramatically reduced following inundation, and the calculated salt concentration in the soil water and shallow groundwater greatly increased. The model simulations showed that recovery depends on several factors, in particular how well the soil in the polder is drained and therefore how well salt is flushed out. Our simulations suggest that with sound maintenance of infrastructure and sound management, particularly of soil drainage, the polders and islands of the Ganges delta could recover fairly quickly from inundation events.

A High-Resolution Flood Inundation Archive (2016–the Present) from Sentinel-1 SAR Imagery over CONUS

AbstractMost existing inundation inventories are based on surveys, news, or passive remote sensing imagery. Affected by spatiotemporal resolution or weather conditions, these inventories are limited in spatial details or coverage. Satellite synthetic aperture radar (SAR) data have recently enabled flood mapping at unprecedented spatiotemporal resolution. However, the bottleneck in producing SAR-based flood maps is the requirement of expert manual processing to maintain acceptable accuracy by most SAR-driven mapping techniques. To fill the vacancy, we generate a high-resolution (10 m) flood inundation dataset over the contiguous United States (CONUS) from nearly the entire Sentinel-1 SAR archive (from January 2016 to the present), using a recently developed automated Radar Produced Inundation Diary (RAPID) system. RAPID uses U.S. Geological Survey (USGS) water watch system and accumulated precipitation to identify SAR images that potentially overlap a flood event. The dataset include inundation events with the temporal scale from several days to months. Concluded from all 559 overlapping images in the period from 2016 to the first half of 2019, the comparison of the proposed dataset against the USGS Dynamic Surface Water Extent (DSWE) product yields an overall, user, producer agreements, and critical success index of 99.06%, 87.63%, 91.76%, and 81.23%, respectively, demonstrating the high accuracy of the proposed dataset and the robustness of the automated system. We anticipate this archive to facilitate many applications, including large-scale flood loss and risk assessment, and inundation model calibration and validation.

Flood modeling of a large transboundary river using WRF-Hydro and microwave remote sensing

The Brahmaputra River, a trans-boundary river between India and Bangladesh experiences large scale floods with frequent inundation events affecting millions of people annually. An integrated approach for quantitative understanding of flood wave characteristics and real time flood modeling framework can be helpful for effective decision making and planning of flood risk management strategies. In this study, we have characterized the flood wave propagation in the Brahmaputra River using gauge observations and model simulations. The spatio-temporal variation of flood lift is estimated using stage hydrograph of different gauge stations along the river. The temporal variation in flood hydrograph is characterized by different flood wave parameters for a gauge station which govern the flood condition in the Brahmaputra River. These flood wave characteristics are used in the categorization of different intensity of flood events. To estimate the river discharge, the WRF-Hydro model was set-up over the Brahmaputra river basin for hourly discharge estimation. The satellite observations form altimeter and Synthetic Aperture Radar (SAR) are used to estimate river flood-plain elevation and inundation. Altimetry data from Jason-3 satellite was used for water level retrieval and compared with gauge and simulated discharge time-series for further validation of model capabilities. Sentinel-1 satellite SAR images are used to assess the flood inundation extent and probability based on flood wave characteristics in the downstream flood-plain region of Guwahati. Finally, we have integrated these data-sets for a flood modeling and forecasting framework for a braided transboundary river system. This integrated system is studied in detail for an extreme event that occurred during July 2019 in the Brahmaputra River. An hourly estimate of each event for the flood period proved the capability of this system for operational deployment in near real-time flood assessment and forecasting purposes for the flood-prone region of South Asia.

Development of a novel hybrid multi-boosting neural network model for spatial prediction of urban flood

In this study, a new hybridized machine learning algorithm for urban flood susceptibility mapping, named MultiB-MLPNN, was developed using a multi-boosting technique and MLPNN. The model was tested in Amol City, Iran, a data-scarce city in an ungauged area which is prone to severe flood inundation events and currently lacks flood prevention infrastructure. Performance of the hybridized model was compared with that of a standalone MLPNN model, random forest and boosted regression trees. Area under the curve, efficiency, true skill statistic, Matthews correlation coefficient, misclassification rate, sensitivity and specificity were used to evaluate model performance. In validation, the MultiB-MLPNN model showed the best predictive performance. The hybridized MultiB-MLPNN model is thus useful for generating realistic flood susceptibility maps for data-scarce urban areas. The maps can be used to develop risk-reduction measures to protect urban areas from devastating floods, particularly where available data are insufficient to support physically based hydrological or hydraulic models.

Terrestrial Morphotypes of Aquatic Plants Display Improved Seed Germination to Deal with Dry or Low-Rainfall Periods.

In temporary ponds, seed germination largely determines how well aquatic plant assemblages recover after dry periods. Some aquatic plants have terrestrial morphotypes that can produce seeds even in dry years. Here, we performed an experiment to compare germination patterns for seeds produced by aquatic and terrestrial morphotypes of Ranunculus peltatus subsp. saniculifolius over the course of five inundation events. During the first inundation event, percent germination was higher for terrestrial morphotype seeds (36.1%) than for aquatic morphotype seeds (6.1%). Seed germination peaked for both groups during the second inundation event (terrestrial morphotype: 47%; aquatic morphotype: 34%). Even after all five events, some viable seeds had not yet germinated (terrestrial morphotype: 0.6%; aquatic morphotype: 5%). We also compared germination patterns for the two morphotypes in Callitriche brutia: the percent germination was higher for terrestrial morphotype seeds (79.5%) than for aquatic morphotype seeds (41.9%). Both aquatic plant species use two complementary strategies to ensure population persistence despite the unpredictable conditions of temporary ponds. First, plants can produce seeds with different dormancy periods that germinate during different inundation periods. Second, plants can produce terrestrial morphotypes, which generate more seeds during dry periods, allowing for re-establishment when conditions are once again favorable.

A New Relative Risk Index for Hospitals Exposed to Tsunami

The failure of hospitals in recent tsunami have caused extensive social and economic losses. A simple but quantitative approach is required to assess the resilience of healthcare systems to tsunami, which relates not only to hospital building integrity, but also to maintaining hospital functionality. This paper proposes a new tsunami relative risk index (TRRI) that quantifies the impact of tsunami on critical units, (e.g. Intensive Care Unit, Maternity Ward, etc) in individual hospitals, as well as the impact on service provision across a network of hospitals. A survey form is specifically developed for collecting of field data on hospitals for the TRRI evaluation. In its current form TRRI is designed for hospital buildings of reinforced concrete construction, as these are the building types most commonly used worldwide for housing critical units. The TRRI is demonstrated through an application to three hospitals located along the southern coast of Sri Lanka. The TRRI is evaluated for three potential tsunami inundation events and is shown to be able to identify issues with both the building and functional aspects of hospital critical units. Three “what-if” intervention scenarios are presented and their effect on the TRRI is assessed. Through this exercise, it is shown that the TRRI can be used by decision makers to simply explore the effectiveness of individual and combined interventions in improving the tsunami resilience of healthcare provision across the hospital system.

An integrated model to predict and prevent hypoxia in floodplain-river systems

Hypoxia can occur following rewetting of floodplains and cause severe impacts on aquatic biota and biogeochemical processes. The likelihood of such events is influenced by a number of factors including temperature, the mass of plant litter on the floodplain (which is influenced by the duration between inundation events), the volume of water available for dilution of oxygen-demanding dissolved organic matter, and the exchange of water to dilute and disperse that material. Using constructed infrastructure to generate managed inundations on floodplains increases the likelihood of hypoxic “blackwater” events relative to unregulated floods, as larger areas of floodplain are inundated at lower flow rates. A model (the “DODOC plugin”) was developed for the Source hydrological modelling software to inform risk mitigation strategies for these managed inundation events. This development enables the interaction between complex hydrology and floodplain inundation on the resulting release of dissolved organic carbon (DOC), and subsequent consumption of dissolved oxygen (DO), to be represented. Key functionality of the plugin includes the ability to represent (i) spatial variability in organic litter build up and degradation, (ii) DOC leaching from litter when inundated, (iii) DO consumption arising from microbial decomposition of the DOC, and (iv) reaeration processes from autotrophic productivity and turbulence as water passes over water level regulating structures. The model is configurable on both river channels (links) and floodplains (storages) to represent changes in DO from both natural and managed inundation events at the scale of an individual floodplain up to multiple floodplains and river reaches. The plugin was parameterised to successfully simulate DOC (R2 = 0.84–0.93) and DO (R2 = 0.74–0.92) along an approx. 100 km study reach of the River Murray in South Australia, once the different behaviour of the labile and refractory components of the DOC was represented in the model. A number of hypothetical operational scenarios were tested using the model to demonstrate parameter sensitivity and to inform planning of managed inundations. The development of the DODOC plugin demonstrates that complex water quality processes can be integrated into the Source (or other) hydrological software, to represent cumulative implications of floodplain inundation events and to minimise the risk of hypoxia.

The ecohydrological impact of water resource developments through inundation regime analysis of a large semi-arid floodplain

The ephemeral inundation of floodplains in semi-arid and arid zone climates is an essential driver of biological productivity. Natural biota depend on floodplain inundation to support critical reproductive life phases. In historical times, grazing industries have developed taking advantage of phases of high productivity associated with the overbank flow. However, the modelling of inundation in lowland floodplains is challenged by the complexity of topographic and hydrodynamic constraints. Here we apply a spatially explicit fine-scale inundation model to compare floodplain inundation regimes associated with current hydrological development on the Darling River floodplain, Australia, and pre-development, conceptualised as the removal of hydrological control structures. Our results suggest that hydrological developments in the Darling River catchment have substantially increased inter-flood period, an effect particularly pronounced during dry climatic phases. The result explains the decline in waterbird utilisation in this section of the Darling River, the low resilience of outer floodplain vegetation to the recent drought, and the reduction in grazing capacity. Water resource development had less impact on large inundation events.

Responses and Recovery of Salt Marsh Vegetation and Birds in Southeastern Massachusetts to Two Hydrologic Events: a Tidal Restoration and an Inundation Event

Allens Pond, a coastal lagoon in southeastern Massachusetts, was subjected to two major hydrological events in the 2000s. The first was a culvert widening to increase tidal flushing in an attempt to stop the spread of the invasive plant, Phragmites australis. The second, four years later, was a complete inundation of the surrounding salt marsh due to the closure of a tidal inlet. The effect of these events on salt marsh vegetation was monitored using transects and on the marsh avian community using point counts. The inundation event, although limited to one growing season, had a more pronounced negative effect on marsh organisms than the restoration. Saltmarsh cordgrass, Spartina alterniflora, took approximately three years to recover to pre-inundation abundance. Salt marsh hay, Spartina patens, had still not recovered five years after the inundation. This supports the idea that this high marsh plant is particularly sensitive to prolonged inundation. There was no measurable effect of either the hydrological restoration or the inundation event on P. australis. Saltmarsh sparrows declined 79% in the years immediately following the inundation, then recovered to their pre-inundation level in about eight years. Seaside sparrows declined 49% immediately following the inundation event and recovered after eight years, although there was a great deal of variation. Willets were only affected in the year immediately after the inundation. Our results from this flooding incident at Allens Pond provide insight into the potential impact of rising sea levels on estuarine plant and avian communities.

Tide-only inundation: a metric to quantify the contribution of tides to coastal inundation under sea-level rise

Sea-level rise is causing coastal inundation events in estuaries, harbours, bays, and tidal rivers to happen more often as predictable daily high and low tides reach higher levels. This can lead to coastal inundation happening under benign weather conditions, as flood thresholds are exceeded due to tides alone without the influence of storm surges or other phenomena. As such, changes in frequency of this 'tide-only' inundation may be a useful metric to quantify the role that sea-level rise plays in modulating the risk of coastal inundation from high still water levels. Here we present a conceptual model for 'tide-only' inundation and propose a practical methodology to formulate tide-only inundation statistics: estimates, historical trends, and future projections. This enables this emerging natural hazard to be fully incorporated into new and existing coastal risk assessment frameworks and considered in coastal management and planning strategies at local and national levels. Further, it leads to a framework that can quantify the role that tides play in coastal flooding as sea levels rise.

An Operational High-Performance Forecasting System for City-Scale Pluvial Flash Floods in the Southwestern Plain Areas of Taiwan

A pluvial flash flood is rapid flooding induced by intense rainfall associated with a severe weather system, such as thunderstorms or typhoons. Additionally, topography, ground cover, and soil conditions also account for the occurrence of pluvial flash floods. Pluvial flash floods are among the most devastating natural disasters that occur in Taiwan, and these floods always /occur within a few minutes or hours of excessive rainfall. Pluvial flash floods usually threaten large plain areas with high population densities; therefore, there is a great need to implement an operational high-performance forecasting system for pluvial flash flood mitigation and evacuation decisions. This study developed a high-performance two-dimensional hydrodynamic model based on the finite-element method and unstructured grids. The operational high-performance forecasting system is composed of the Weather Research and Forecasting (WRF) model, the Storm Water Management Model (SWMM), a two-dimensional hydrodynamic model, and a map-oriented visualization tool. The forecasting system employs digital elevation data with a 1-m resolution to simulate city-scale pluvial flash floods. The extent of flooding during historical inundation events derived from the forecasting system agrees well with the surveyed data for plain areas in southwestern Taiwan. The entire process of the operational high-performance forecasting system prediction of pluvial flash floods in the subsequent 24 h is accomplished within 8–10 min, and forecasts are updated every six hours.

Seasonal climate summary for Australia and the southern hemisphere (summer 2018–19): extreme heat and flooding prominent

This is a summary of the southern hemisphere atmospheric circulation patterns and meteorological indices for summer 2018–19; an account of seasonal rainfall and temperature for the Australian region is also provided. January 2019 was Australia’s hottest month on record, nearly 1°C warmer than any previous month. Impacts of heavy rain and floods were reported in Australia, New Zealand and South American nations. Extreme terrestrial and maritime heatwaves occurred in and around Australia and New Zealand. Case studies of the Australian heatwave, Queensland floods in January and February, and a tide-driven coastal inundation event are considered.

EXPERIMENTAL DATA AND NUMERICAL SIMULATION OF WAVE LOADING AND ITS REDUCTION ON SHELTERED BUILDINGS

Wave loading from inundation events like storms and tsunamis can cause severe structural damage to buildings (Xian et al., 2015); therefore, it is important to predict wave loading as accurately as possible. One uncertainty in estimating wave loads during inundation events is the possible reduction of loads by sheltering from other buildings. Understanding and quantifying this effect could reduce overestimated loads in sheltered buildings and avoid over-conservative structural design. This work aims to quantify the reduction of wave loads in sheltered buildings through the analysis of experimental data and numerical simulations.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/89QblLjDBnI

Dissipation Effects of Coastal Vegetation on Nearshore Structures under Wave Runup Loading

Inundation events caused by hurricanes or tsunamis pose a substantial risk to the integrity of coastal infrastructure; however, their impact on the built environment can be greatly altered by natural and anthropogenic obstacles or disturbances to the flow, such as vegetation or neighboring structures. This paper investigates the impact of coastal vegetation on shoreline structural vulnerability due to wave runup loading. Using numerical simulation data, the load (base shear) and momentum flux are computed as a function of vegetation characteristics (length and density) for different excitation intensities (wave heights) at the location of a shoreline structure. This information is then used to estimate structural fragility. Motivated by recent reconnaissance data from Hurricane Matthew in 2016, emphasis is placed on the out-of-plane failure of infill masonry walls. Extension to a different structural typology, that of a reinforced concrete frame, is also discussed. Comparisons between different vegetation characteristics and the bare-earth case demonstrate the wave dissipation and reduction of structural fragility (and therefore ultimately vulnerability) achieved when vegetation is present for the investigated case-study structures.

Coral boulder transport and gravel bar formation by storms in Lumaniag village, Batangas, northwestern Philippines

The contribution of tropical storms to a carbonate gravel bar formation is presented for Lumaniag village, northwestern Philippines, based on field measurements, high-precision UTh dating of Porites sp. coral boulders (longest axis > 1 m), historical records of tsunamigenic earthquakes and typhoons, and anecdotal accounts. Results of UTh dating suggest that the events which transported the sampled fully exposed boulders found on the gravel bar occurred during the 1960s to early 1970s; the underlying rubble are presumed to have been deposited by older inundation events. The UTh ages are consistent with anecdotal accounts and records of typhoon tracks and damage reports from typhoons Dading (international name Winnie; 1964), Welming (international name: Emma; 1967), and several other strong typhoons in early 1970s. Hydrodynamic calculations estimate a minimum flow velocity of 3.2 m/s to initiate translocation of the largest coral boulders in the area. Potential shift in storm frequency and intensity over the next few decades suggests that the gravel bar will further accumulate carbonate sediments. With the mangroves contributing to its stability, the storm-deposited island-like feature contributes to the dissipation of approaching storm waves and provides natural protection for the nearby coastal community. The ridge will likely provide an effective buffer for extreme waves in the term unless destroyed by anthropogenic activities or an oversized extreme event.