Khan, N.S., B.P. Horton, K.L. McKee, D. Jerolmack, F. Falcini, M.D. Enache, and C.H. Vane, 2013: “Tracking sedimentation from the historic A.D. 2011 Mississippi River flood in the deltaic wetlands of Louisiana, USA.” Geology, doi: 10.1130/G33805.1.
Management and restoration of the Mississippi River deltaic plain (southern United States) and associated wetlands require a quantitative understanding of sediment delivery during large flood events, past and present. Here, we investigate the sedimentary fingerprint of the 2011 Mississippi River flood across the Louisiana coast (Atchafalaya Delta, Terrebonne, Barataria, and Mississippi River Delta basins) to assess spatial patterns of sedimentation and to identify key indicators of sediment provenance. The sediment deposited in wetlands during the 2011 flood was distinguished from earlier deposits based on biological characteristics, primarily absence of plant roots and increased presence of centric (planktonic) diatoms indicative of riverine origin. By comparison, the lithological (bulk density, organic matter content, and grain size) and chemical (stable carbon isotopes of bulk organic matter) properties of flood sediments were nearly identical to the underlying deposit. Flood sediment deposition was greatest in wetlands near the Atchafalaya and Mississippi Rivers and accounted for a substantial portion (37% to 85%) of the annual accretion measured at nearby monitoring stations. The amount of sediment delivered to those basins (1.1–1.6 g cm–2) was comparable to that reported previously for hurricane sedimentation along the Louisiana coast (0.8–2.1 g cm–2). Our findings not only provide insight into how large-scale river floods influence wetland sedimentation, they lay the groundwork for identifying previous flood events in the stratigraphic record.
Falcini, F., N.S. Khan, L. Macelloni, B.P. Horton, C.B. Lutken, K.L. McKee, R. Santoleri, S. Colella, C. Li, G. Volpe, M. D’Emidio, A. Salusti, and D.J. Jerolmack, 2012: “Linking the historic 2011 Mississippi River flood to coastal wetland sedimentation.” Nature Geoscience, v. 5, pp. 803-807, doi: 10.1038/ngeo1615.
Wetlands in the Mississippi River deltaic plain are deteriorating in part because levees and control structures starve them of sediment. In spring 2011 a record-breaking flood brought discharge on the lower Mississippi River to dangerous levels, forcing managers to divert up to 3,500 m3 s−1 of water to the Atchafalaya River Basin. Here we use field-calibrated satellite data to quantify differences in inundation and sediment-plume patterns between the Mississippi and Atchafalaya River. We assess the impact of these extreme outflows on wetland sedimentation, and use in situ data collected during the historic flood to characterize the Mississippi plume’s hydrodynamics and suspended sediment. We show that a focused, high-momentum jet emerged from the leveed Mississippi, and delivered sediment far offshore. In contrast, the plume from the Atchafalaya was more diffuse; diverted water inundated a large area, and sediment was trapped within the coastal current. The largest sedimentation, of up to several centimetres, occurred in the Atchafalaya Basin despite the larger sediment load carried by the Mississippi. Sediment accumulation was lowest along the shoreline between the two river sources. We conclude that river-mouth hydrodynamics and wetland sedimentation patterns are mechanistically linked, providing results that are relevant for plans to restore deltaic wetlands using artificial diversions.
Andersen, T.K., and J.M. Shepherd, 2013: “Floods in a changing climate.” Geography Compass, v. 7, pp. 95-115, doi: 10.1111/gec3.12025.
Atmospheric warming and associated hydrological changes have implications for regional flood intensity and frequency. Climate models and hydrological models have the ability to integrate various contributing factors and assess potential changes to hydrology at global to local scales through the century. This survey of floods in a changing climate reviews flood projections based on sources of precipitation, ice and snow melt, and coastal inundation. Topographic and anthropogenic influences that exacerbate or reduce flood risks by altering surface runoff, infiltration, storage, and precipitation development are also considered. Flood mitigation and adaptation strategies for infrastructure, agriculture, public health, and local communities are explored along with uncertainties and challenges in flood research. Recent and upcoming datasets to help with future flood monitoring and prediction include satellite missions, advanced radar, and in-situ networks.
Aerts, J.C.J.H., N. Lin, W.J.W. Botzen, K. Emanuel, and H. de Moel, 2013: “Low-probability flood risk modeling for New York City.” Risk Analysis, doi: 10.1111/risa.12008.
The devastating impact by Hurricane Sandy (2012) again showed New York City (NYC) is one of the most vulnerable cities to coastal flooding around the globe. The low-lying areas in NYC can be flooded by nor’easter storms and North Atlantic hurricanes. The few studies that have estimated potential flood damage for NYC base their damage estimates on only a single, or a few, possible flood events. The objective of this study is to assess the full distribution of hurricane flood risk in NYC. This is done by calculating potential flood damage with a flood damage model that uses many possible storms and surge heights as input. These storms are representative for the low-probability/high-impact flood hazard faced by the city. Exceedance probability-loss curves are constructed under different assumptions about the severity of flood damage. The estimated flood damage to buildings for NYC is between US$59 and 129 millions/year. The damage caused by a 1/100-year storm surge is within a range of US$2 bn–5 bn, while this is between US$5 bn and 11 bn for a 1/500-year storm surge. An analysis of flood risk in each of the five boroughs of NYC finds that Brooklyn and Queens are the most vulnerable to flooding. This study examines several uncertainties in the various steps of the risk analysis, which resulted in variations in flood damage estimations. These uncertainties include: the interpolation of flood depths; the use of different flood damage curves; and the influence of the spectra of characteristics of the simulated hurricanes.
Lavers, D.A., G. Villarini, R.P. Allan, E.F. Wood, and A.J. Wade, 2012: “The detection of atmospheric rivers in atmospheric reanalyses and their links to British winter floods and the large-scale climatic circulation.” Journal of Geophysical Research, v. 117, paper no. D20106, doi: 10.1029/2012JD018027.
Atmospheric Rivers (ARs), narrow plumes of enhanced moisture transport in the lower troposphere, are a key synoptic feature behind winter flooding in midlatitude regions. This article develops an algorithm which uses the spatial and temporal extent of the vertically integrated horizontal water vapor transport for the detection of persistent ARs (lasting 18 h or longer) in five atmospheric reanalysis products. Applying the algorithm to the different reanalyses in the vicinity of Great Britain during the winter half-years of 1980–2010 (31 years) demonstrates generally good agreement of AR occurrence between the products. The relationship between persistent AR occurrences and winter floods is demonstrated using winter peaks-over-threshold (POT) floods (with on average one flood peak per winter). In the nine study basins, the number of winter POT-1 floods associated with persistent ARs ranged from approximately 40 to 80%. A Poisson regression model was used to describe the relationship between the number of ARs in the winter half-years and the large-scale climate variability. A significant negative dependence was found between AR totals and the Scandinavian Pattern (SCP), with a greater frequency of ARs associated with lower SCP values.
Villarini, G., J.A. Smith, R. Vitolo, and D.B. Stephenson, 2013: “On the temporal clustering of US floods and its relationship to climate teleconnection patterns.” International Journal of Climatology, v. 33, pp. 629–640, doi: 10.1002/joc.3458.
This article examines whether the temporal clustering of flood events can be explained in terms of climate variability or time-varying land-surface state variables. The point process modelling framework for flood occurrence is based on Cox processes, which can be represented as Poisson processes with randomly varying rate of occurrence. In the special case that the rate of occurrence is deterministic, the Cox process simplifies to a Poisson process. Poisson processes represent flood occurrences which are not clustered. The Cox regression model is used to examine the dependence of the rate of occurrence on covariate processes. We focus on 41 stream gauge stations in Iowa, with discharge records covering the period 1950–2009. The climate covariates used in this study are the North Atlantic Oscillation (NAO) and the Pacific/North American Teleconnection (PNA). To examine the influence of land-surface forcing on flood occurrence, the antecedent 30 d rainfall accumulation is considered. In 27 out of 41 stations, either PNA or NAO, or both are selected as significant predictors, suggesting that flood occurrence in Iowa is influenced by large-scale climate indices. Antecedent rainfall, used as a proxy for soil moisture, plays an important role in driving the occurrence of flooding in Iowa. These results point to clustering as an important element of the flood occurrence process.
Lund, J.R., 2012: “Flood management in California.” Water, v. 4, pp. 157-169, doi: 10.3390/w4010157.
California’s development and success have been shaped by its ability to manage floods. This management has varied over the history of California’s economic and political development and continues in various forms today. California will always have flood problems. A range of options are available to aid in flood management problems and have been used over time. These options can be contrasted with flood management elsewhere and the types of options used to manage other types of hazards in California, such as earthquakes, wildfires, and droughts. In the future, flood management in California will require greater reliance on local funding and leadership, reflecting diminished federal and state funding, with more effective state and federal guidance. Effective flood management will also tend to integrate flood management with actions to achieve environmental and other water supply objectives, both to gain revenues from a broader range of beneficiaries as well as to make more efficient use of land and water in a state where both are often scarce.
Frappart, F., G. Ramillien, and J. Ronchail, 2013: “Changes in terrestrial water storage versus rainfall and discharges in the Amazon basin.” International Journal of Climatology, doi: 10.1002/joc.3647.
This study examines how the interannual variability of rainfall impacts the land water storage in the Amazon basin during the 2003–2010 time span at monthly time-scale using respectively, Tropical Rainfall Measuring Mission (TRMM) and Gravity Recovery And Climate Experiment (GRACE) satellite observations. Monthly estimates of GRACE-based terrestrial water storage (TWS) are compared to (1) TRMM rainfall, (2) in situ discharges at the outlet of the major sub-basins of the Amazon over 2003–2010 to characterize the redistribution of precipitation on land water. The time-variations of land water storage derived from GRACE are consistent with those of rainfall and discharges at basin and sub-basin scales even at interannual time-scales (correlation generally greater than 0.7). The study of the relationship between these two quantities reveals large differences in terms of rainfall amount, water storage, time delays, resulting of the water transport among the sub-basins of the Amazon. The analysis of GRACE data has enabled identification of the signature of the recent extreme climatic events (droughts of 2005 and 2010, flood of 2009) on the land water storage, in terms of spatial patterns and intensity. These results are in good agreement with what was observed on independent datasets (water levels and discharges, vegetation activity, forest fires, and drought index), highlighting the interest of gravimetry from space missions for the characterization of the interannual variability of the TWS. GRACE data offer the unique opportunity to monitor the hydrological cycle in ungauged basins where reliable observations of rainfall and discharges are missing.
Apisarnthanarak, A., L.M. Mundy, T. Khawcharoenporn, and C.G. Mayhall, 2013: “Hospital infection prevention and control issues relevant to extensive floods.” Infection Control and Hospital Epidemiology, v. 34, pp. 200-206, doi: 10.1086/669094.
The devastating clinical and economic implications of floods exemplify the need for effective global infection prevention and control (IPC) strategies for natural disasters. Reopening of hospitals after excessive flooding requires a balance between meeting the medical needs of the surrounding communities and restoration of a safe hospital environment. Postflood hospital preparedness plans are a key issue for infection control epidemiologists, healthcare providers, patients, and hospital administrators. We provide recent IPC experiences related to reopening of a hospital after extensive black-water floods necessitated hospital closures in Thailand and the United States. These experiences provide a foundation for the future design, execution, and analysis of black-water flood preparedness plans by IPC stakeholders.
Martius, O., H. Sodemann, H. Joos, S. Pfahl, A. Winschall, M. Croci-Maspoli, M. Graf, E. Madonna, B. Mueller, S. Schemm, J. Sedláček, M. Sprenger, and H. Wernli, 2012: “The role of upper-level dynamics and surface processes for the Pakistan flood of July 2010.” Quarterly Journal of the Royal Meteorological Society, doi: 10.1002/qj.2082.
In July and August 2010 floods of unprecedented impact afflicted Pakistan. The floods resulted from a series of intense multi-day precipitation events in July and early August. At the same time a series of blocking anticyclones dominated the upper-level flow over western Russia and breaking waves i.e. equatorward extrusions of stratospheric high potential vorticity (PV) air formed along the downstream flank of the blocks. Previous studies suggested that these extratropical upper-level breaking waves were crucial for instigating the precipitation events in Pakistan. Here a detailed analysis is provided of the extratropical forcing of the precipitation. Piecewise PV inversion is used to quantify the extratropical upper-level forcing associated with the wave breaking and trajectories are calculated to study the pathways and source regions of the moisture that precipitated over Pakistan. Limited-area model simulations are carried out to complement the Lagrangian analysis.
The precipitation events over Pakistan resulted from a combination of favourable boundary conditions with strong extratropical and monsoonal forcing factors. Above-normal sea-surface temperatures in the Indian Ocean led to an elevated lower-tropospheric moisture content. Surface monsoonal depressions ensured the transport of moist air from the ocean towards northeastern Pakistan. Along this pathway the air parcel humidity increased substantially (60–90% of precipitated moisture) via evapotranspiration from the land surface. Extratropical breaking waves influenced the surface wind field substantially by enhancing the wind component directed towards the mountains which reinforced the precipitation.