A global analysis of the interplay between flood severity ad human dynamics in floodplains

<p>This study aims at exploring whether changes in the spatial distribution of the human population and the built-up areas within floodplains can be associated with extreme flood events generating severe economic losses and fatalities. We relate economic losses and fatalities caused by floods during 1990&#8208;2000, with changes in human population and built&#8208;up areas in floodplains during 2000&#8208;2015 by exploiting global archives as the Global Human Settlement, GFPLAIN250m, and the EM-DAT datasets. Despite the frequent flood losses in the previous period 1990&#8208;2000, we found that population and built&#8208;up areas in floodplains increased in the period 2000&#8208;2015 for the majority of the analyzed countries. On the other hand, we observed a reduction in floodplains population after more severe flood losses that occurred in the period 1975&#8208;2000. Finally, floodplains population increased after a period of high flood fatalities in low&#8208;income countries, while built&#8208;up areas increased after a period of frequent economic losses in upper&#8208;middle and high&#8208;income countries. This study can be used as a general framework for advancing knowledge of human&#8208;flood interactions and support the development of sustainable policies and measures for flood risk management and disaster risk reduction.</p>

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Analysis of the Most Severe Flood Events in Turkey (1960–2014): Which Triggering Mechanisms and Aggravating Pathways Can be Identified?

Water ◽

10.3390/w12061562 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1562

Author(s):

Gamze Koç ◽

Theresia Petrow ◽

Annegret Thieken

Keyword(s):

Influencing Factor ◽

Extreme Rainfall ◽

Hierarchical Cluster ◽

Dominant Factor ◽

Economic Losses ◽

Soil Conditions ◽

Flood Events ◽

Severe Flood ◽

Catchment Size ◽

Triggering Mechanisms

The most severe flood events in Turkey were determined for the period 1960–2014 by considering the number of fatalities, the number of affected people, and the total economic losses as indicators. The potential triggering mechanisms (i.e., atmospheric circulations and precipitation amounts) and aggravating pathways (i.e., topographic features, catchment size, land use types, and soil properties) of these 25 events were analyzed. On this basis, a new approach was developed to identify the main influencing factor per event and to provide additional information for determining the dominant flood occurrence pathways for severe floods. The events were then classified through hierarchical cluster analysis. As a result, six different clusters were found and characterized. Cluster 1 comprised flood events that were mainly influenced by drainage characteristics (e.g., catchment size and shape); Cluster 2 comprised events aggravated predominantly by urbanization; steep topography was identified to be the dominant factor for Cluster 3; extreme rainfall was determined as the main triggering factor for Cluster 4; saturated soil conditions were found to be the dominant factor for Cluster 5; and orographic effects of mountain ranges characterized Cluster 6. This study determined pathway patterns of the severe floods in Turkey with regard to their main causal or aggravating mechanisms. Accordingly, geomorphological properties are of major importance in large catchments in eastern and northeastern Anatolia. In addition, in small catchments, the share of urbanized area seems to be an important factor for the extent of flood impacts. This paper presents an outcome that could be used for future urban planning and flood risk prevention studies to understand the flood mechanisms in different regions of Turkey.

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Extreme flood events and their frequency variations during the middle to late-Holocene recorded in the sediment of Lake Suigetsu, central Japan

The Holocene ◽

10.1177/0959683620961497 ◽

2020 ◽

Vol 31 (1) ◽

pp. 121-133

Author(s):

Yoshiaki Suzuki ◽

Ryuji Tada ◽

Kana Nagashima ◽

Takeshi Nakagawa ◽

Katsuya Gotanda ◽

...

Keyword(s):

Late Holocene ◽

Temporal Variations ◽

Continental Margins ◽

Flood Events ◽

Central Japan ◽

Westerly Jet ◽

Extreme Flood ◽

Western Japan ◽

High Flood ◽

Event Layers

Many studies are reconstructing flood records in the continental margins during the middle to late-Holocene. However, distinguishing the frequency and magnitude of flood events was difficult. Light gray event layers (GELs) in the sediment of Lake Suigetsu in Central Japan can solve this problem because they are recording the occurrence and magnitude of flood events during the last 80 years. Using these GELs, we aimed to reconstruct the frequency and magnitude of flood events during the last 8000 years. First, we verified whether GELs maintained the recording of flood events. We found that thin GELs (less than 40 mg/cm2 in mass) were rare, probably because of bioturbation, whereas thick GELs (larger than 40 mg/cm2 in mass) were rarely erased. We also found that GELs formed by the same amount of rainfall could have been thinner before 100 years ago. We revealed that the occurrence of extreme flood-origin event layers (EFELs: GELs thicker than 40 mg/cm2) during the last 8000 years may indicate the occurrence of extreme flood events (EFEs). Mass accumulation of EFELs may indicate the minimum estimation of rainfall on EFEs. There are several periods with higher frequency and magnitude of EFEs than those of the present level, agreeing with the periods of high flood activity in western Japan and East China. The frequency and magnitude of EFEs show different temporal variations. Northward and southward shifts in the westerly jet and monsoon fronts can partially explain such patterns.

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Repeated flood disturbance enhances rotifer dominance and diversity in a zooplankton community of a small dammed mountain pond

Journal of Limnology ◽

10.4081/jlimnol.2016.1544 ◽

2016 ◽

Cited By ~ 2

Author(s):

Carmen Gabaldón ◽

Miloslav Devetter ◽

Josef Hejzlar ◽

Karel Šimek ◽

Petr Znachor ◽

...

Keyword(s):

Biotic Interactions ◽

Zooplankton Community ◽

High Ratio ◽

Flood Events ◽

Physical Conditions ◽

Short Period ◽

Extreme Flood ◽

Zero Values ◽

Colonization Ability ◽

High Flood

<p>The zooplankton community in a relatively small and mountain pond was studied during the spring growing season. To investigate which factors operate in the community structure, we explored several physical conditions, such as high inflows, and the biotic dynamics of the main zooplankton groups (i.e., rotifers, cladocerans and copepods). Two extreme flood events occurred during the investigated period and caused dramatic changes in physical conditions and reduction of the planktonic community abundances. The short period between both high-flow events was enough for the recovery of microplankton, but not for the metazoan zooplankton. Our results are in agreement with the common situation in which high flood events commonly favour rotifers over crustaceans, likely due to rotifer species have great colonization ability and grow faster. However, we found that the dominance of rotifers over crustaceans in our system is evidenced by an extremely, unusual high ratio between their abundances. We observed that, at the time of the great floods, crustacean abundances as well as rotifer populations notably decreased until near zero values. Although rotifer abundance began declining before high floods, the decrease was particularly notable when the great flood happened. Our results evidenced that i) dilution rate and temperature were the main drivers which are operating in the structure of the zooplankton community; and ii) no negative biotic interactions were detected between large and small cladocerans and rotifers. Additionally, we found surprisingly that a repeated disturbance caused by high flood events does increase the species diversity of rotifers. Finally, our study also detected some cues which may indicate that diapausing egg bank is also playing an important role in the zooplankton community, favouring the dominance of rotifers; however, this phenomenon deserves further studies. </p>

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Developing an Automated Medium-Range Flood Awareness System for Switzerland Based on Probabilistic Forecasts of Integrated Water Vapor Fluxes

Weather and Forecasting ◽

10.1175/waf-d-18-0189.1 ◽

2019 ◽

Vol 34 (6) ◽

pp. 1759-1776

Author(s):

Irina Mahlstein ◽

Jonas Bhend ◽

Christoph Spirig ◽

Olivia Martius

Keyword(s):

Warning System ◽

Flood Damage ◽

Economic Losses ◽

Flood Events ◽

Weather Forecasts ◽

Flood Warning ◽

Probabilistic Forecasts ◽

Extreme Flood ◽

Medium Range ◽

Flood Warning System

Abstract Floods in the Alpine region can be destructive and cause large economic losses. Many rivers and lakes in Switzerland are regulated and flood damage can be mitigated through an optimal management of lake levels and runoff. This requires high-quality forecasts of atmospheric flood precursors extending beyond short-range (forecast days 1–5) predictions. In several places around the world atmospheric rivers or extreme integrated vapor transport (IVT) are causally related to flood events. Also in Switzerland, extreme IVT oriented perpendicular to the main orography heralds extreme flood events. This relationship is exploited in an operational flood warning system on the medium-range (here forecast days 6–10) time scale based on probabilistic medium-range forecasts of IVT and precipitation over Switzerland provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS). This entails first a comprehensive probabilistic verification of the direction and magnitude of (extreme) IVT and second the development of compact visualizations for the operational use by hydrologists. Based on 20 years of probabilistic reforecasts, we show that both regular and extreme IVT has a better predictability than precipitation and IVT is predictable out to day 8. As the direction of IVT is of central importance for flood risk in Switzerland, we develop a visualization that summarizes probabilistic information on both the direction and magnitude of the IVT together with users of the product. The result is an operational flood warning system based solely on atmospheric flood precursors to extend flood warning information beyond the range of high-resolution deterministic weather forecasts.

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Ectomycorrhiza resilience and recovery to extreme flood events in Tuber aestivum and Quercus robur

Mycorrhiza ◽

10.1007/s00572-021-01035-4 ◽

2021 ◽

Author(s):

P. W. Thomas

Keyword(s):

Climate Change ◽

Seedling Growth ◽

Quercus Robur ◽

Root Systems ◽

Fruiting Bodies ◽

Flood Events ◽

Tuber Aestivum ◽

Soil Zone ◽

Extreme Flood ◽

The Impact

AbstractVery little is known about the impact of flooding and ground saturation on ectomycorrhizal fungi (EcM) and increasing flood events are expected with predicted climate change. To explore this, seedlings inoculated with the EcM species Tuber aestivum were exposed to a range of flood durations. Oak seedlings inoculated with T. aestivum were submerged for between 7 and 65 days. After a minimum of 114-day recovery, seedling growth measurements were recorded, and root systems were destructively sampled to measure the number of existing mycorrhizae in different zones. Number of mycorrhizae did not display correlation with seedling growth measurements. Seven days of submersion resulted in a significant reduction in mycorrhizae numbers and numbers reduced most drastically in the upper zones. Increases in duration of submersion further impacted mycorrhizae numbers in the lowest soil zone only. T. aestivum mycorrhizae can survive flood durations of at least 65 days. After flooding, mycorrhizae occur in higher numbers in the lowest soil zone, suggesting a mix of resilience and recovery. The results will aid in furthering our understanding of EcM but also may aid in conservation initiatives as well as providing insight for those whose livelihoods revolve around the collection of EcM fruiting bodies or cropping of the plant partners.

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