scholarly journals A sub-centennial-scale optically stimulated luminescence chronostratigraphy and late Holocene flood history from a temperate river confluence

Geology ◽  
2020 ◽  
Vol 48 (8) ◽  
pp. 819-825 ◽  
Author(s):  
Ben Pears ◽  
Antony G. Brown ◽  
Phillip S. Toms ◽  
Jamie Wood ◽  
David Sanderson ◽  
...  
Keyword(s):  
Land Use ◽  
Accumulation Rate ◽  
Optically Stimulated Luminescence ◽  
Ice Age ◽  
Flood Events ◽  
14C Dating ◽  
Flood Duration ◽  
Flood Magnitude ◽  
High Flood ◽  
Flood Intensity

Abstract River confluences can be metastable and contain valuable geological records of catchment response to decadal- to millennial-scale environmental change. However, in alluvial reaches, flood stratigraphies are particularly hard to date using 14C. In this paper, we use a novel combination of optically stimulated luminescence and multiproxy sedimentological analyses to provide a flood record for the confluence of the Rivers Severn and Teme (United Kingdom) over the past two millennia, which we compare with independent European climate records. The results show that by ca. 2000 yr B.P., the Severn-Teme confluence had stabilized and overbank alluviation had commenced. Initially, this occurred from moderately high flood magnitudes between ca. 2000 and 1800 yr B.P. (50 BCE–150 CE), but was followed from 1800 to 1600 yr B.P. (150–350 CE) by fine alluvial deposition and decreased flood intensity. From 1600 to 1400 yr B.P. (350–550 CE), the accumulation rate increased, with evidence of large flood events associated with the climatic deterioration of the Dark Age Cold Period. Following a period of reduced flood activity after ca. 1400 yr B.P. (ca. 550 CE), larger flood events and increase in accumulation rate once again became more prevalent from ca. 850 yr B.P. (ca. 1100 CE), coincident with the start of the Medieval Climate Anomaly, a period associated with warmer, wetter conditions and increased land-use intensity. This state persisted until ca. 450 yr B.P. (ca. 1500 CE), after which increased flood magnitudes can be associated with climatic variations during the Little Ice Age. We demonstrate that from the combination of high-resolution dating techniques and multiple analytical parameters, distinctive phases of relative flood magnitude versus flood duration can be determined to a detailed chronological precision beyond that possible from 14C dating. This permits the identification of the regional factors behind floodplain sedimentation, which we correlate with the intensification of land-use and climatic drivers over the last two millennia.

scholarly journals Quantifying the contribution of flood intensity indicators with the projection pursuit model

2017 ◽  
Vol 49 (1) ◽  
pp. 60-71 ◽  
Author(s):  
Lina Wang ◽  
Yanqing Lian ◽  
Xiaohong Chen
Keyword(s):  
Southern China ◽  
Projection Pursuit ◽  
Flood Events ◽  
Flood Duration ◽  
Flood Discharge ◽  
Wujiang River ◽  
Flood Volume ◽  
Projection Pursuit Model ◽  
Flood Intensity ◽  
Peak Flood

Abstract Identifying the various factors that affect the intensity of a flood event, such as its duration and volume, is essential for strategic planning and flood management. Further, quantifying the impacts of these major factors on flood intensity using the contribution rate is essential, but technically challenging. In this study, the authors have adopted the projection pursuit model to quantify the contribution rates of peak flood stage and peak flood discharge, flood duration, and total flood volume (the maximum 12-, 24-, and 72-hour flood volumes) in the Wujiang River in Southern China. This study showed that peak flood discharge and total flood volume were the two dominant factors impacting flood intensity. Although flood duration can be a major factor for some flood events, it contributed the least to flood intensity for most of the historic flood events studied. Likewise, the maximum 24-hour and 72-hour flood volumes contributed little to flood intensity. Findings from this study not only demonstrated the successful adoption of the projection pursuit model for contribution rates, but also provided critical information for planning and managing the regional hydraulic resources in the Wujiang River.

scholarly journals Frequency and intensity of palaeofloods at the interface of Atlantic and Mediterranean climate domains

2016 ◽  
Vol 12 (2) ◽  
pp. 299-316 ◽  
Author(s):  
B. Wilhelm ◽  
H. Vogel ◽  
C. Crouzet ◽  
D. Etienne ◽  
F. S. Anselmetti
Keyword(s):  
20Th Century ◽  
High Intensity ◽  
Volcanic Eruptions ◽  
Warming Trend ◽  
Flood Frequency ◽  
Ice Age ◽  
European Alps ◽  
Flood Events ◽  
Future Evolution ◽  
Flood Intensity

Abstract. Mediterranean climatic influences was explored by studying a lake sequence (Lake Foréant) of the Western European Alps. High-resolution sedimentological and geochemical analysis revealed 171 event layers, 168 of which result from past flood events over the last millennium. The layer thickness was used as a proxy of intensity of past floods. Because the Foréant palaeoflood record is in agreement with the documented variability of historical floods resulting from local and mesoscale, summer-to-autumn convective events, it is assumed to highlight changes in flood frequency and intensity related to such events typical of both Atlantic (local events) and Mediterranean (mesoscale events) climatic influences. Comparing the Foréant record with other Atlantic-influenced and Mediterranean-influenced regional flood records highlights a common feature in all flood patterns that is a higher flood frequency during the cold period of the Little Ice Age (LIA, AD 1300–1900). In contrast, high-intensity flood events are apparent during both the cold LIA and the warm Medieval Climate Anomaly (MCA, AD 950–1250). However, there is a tendency towards higher frequencies of high-intensity flood events during the warm MCA. The MCA extremes could mean that under the global warming scenario, we might see an increase in intensity (not in frequency). However, the flood frequency and intensity in the course of the 20th century warming trend did not change significantly. Uncertainties in future evolution of flood intensity lie in the interpretation of the lack of 20th century extremes (transition or stable?) and the different climate forcing factors between the two periods (greenhouse gases vs. solar and/or volcanic eruptions).

Statistical Analysis of Major Flood Events During 1980-2015 in Middle Ganga Plain, Ganga River Basin, India

2020 ◽  
pp. 225-241
Author(s):  
Aman Arora ◽  
Masood Ahsan Siddiqui ◽  
Manish Pandey
Keyword(s):  
Statistical Analysis ◽  
River Basin ◽  
Graphical Representation ◽  
Ganga River ◽  
Ganga Plain ◽  
Flood Events ◽  
Flood Duration ◽  
Middle Ganga Plain ◽  
Flood Magnitude ◽  
Severity Class

To understand the vicious nature of extreme flood events for the most flood prone region of Ganga River Basin, this study uses 36 years (1980-2015) of flood records from Dartmouth Flood Observatory (DFO) and the Centre for Research on the Epidemiology of Disasters (CRED) Emergency Events Database (EM-DAT). Further, the Water Level (WL) data collected from Central Water Commission (CWC) for same period are utilized to compare with the data of DFO and EM-DAT to identify the major flood events recorded in the Middle Ganga Plain (MGP). The final dataset comprises of 15 attributes (parameters) and is prepared of identified 99 flood instances for statistical analysis. The descriptive statistical analysis is performed for the following parameters: severity class, flood duration in days, affected flood area, flood magnitude, total number of deaths, and total count of displaced people. The graphical representation of all selected parameters provides an insight of common flood events, which lie between ±95% confidence level and exclude the major events as outliers.

scholarly journals The history of settlement and agrarian land use in a boreal forest in Värmland, Sweden, new evidence from pollen analysis

2021 ◽  
Author(s):  
Sigrún Dögg Eddudóttir ◽  
Eva Svensson ◽  
Stefan Nilsson ◽  
Anneli Ekblom ◽  
Karl-Johan Lindholm ◽  
...  
Keyword(s):  
Land Use ◽  
Pollen Analysis ◽  
Large Scale ◽  
Pollen Grains ◽  
Ice Age ◽  
Valuable Insight ◽  
Archaeological Survey ◽  
History Of ◽  
New Evidence ◽  
Insight Into

AbstractShielings are the historically known form of transhumance in Scandinavia, where livestock were moved from the farmstead to sites in the outlands for summer grazing. Pollen analysis has provided a valuable insight into the history of shielings. This paper presents a vegetation reconstruction and archaeological survey from the shieling Kårebolssätern in northern Värmland, western Sweden, a renovated shieling that is still operating today. The first evidence of human activities in the area near Kårebolssätern are Hordeum- and Cannabis-type pollen grains occurring from ca. 100 bc. Further signs of human impact are charcoal and sporadic occurrences of apophyte pollen from ca. ad 250 and pollen indicating opening of the canopy ca. ad 570, probably a result of modification of the forest for grazing. A decrease in land use is seen between ad 1000 and 1250, possibly in response to a shift in emphasis towards large scale commodity production in the outlands. Emphasis on bloomery iron production and pitfall hunting may have caused a shift from agrarian shieling activity. The clearest changes in the pollen assemblage indicating grazing and cultivation occur from the mid-thirteenth century, coinciding with wetter climate at the beginning of the Little Ice Age. The earliest occurrences of anthropochores in the record predate those of other shieling sites in Sweden. The pollen analysis reveals evidence of land use that predates the results of the archaeological survey. The study highlights how pollen analysis can reveal vegetation changes where early archaeological remains are obscure.

Contextualized sedimentation rates for large floods along the lower Mississippi River: the importance of flood duration

2021 ◽  
Author(s):  
Paul Hudson ◽  
Franklin Heitmuller ◽  
Samuel Muñoz ◽  
Jansen Costello
Keyword(s):  
Suspended Sediment ◽  
Sedimentation Rate ◽  
Field Data ◽  
Flood Events ◽  
Sediment Thickness ◽  
Flood Duration ◽  
Sedimentary Deposits ◽  
Sand Sheet ◽  
Overbank Sedimentation ◽  
Sampling Procedures

<p>Flood sedimentary deposits vary due to upper basin and lower basin controls. In this study we focus on overbank sediment thickness, which over longer periods drives changes to riparian aquatic habitat and floodplain construction. The study setting is a ~25 km long segment of the lower Mississippi alluvial valley, between Natchez, MS and Red River Landing, LA. We report new field data for overbank sedimentation generated by compound flooding over 2018 and 2019 hydrologic years, and compare with sedimentation data from prior large flood events. Overbank conditions in 2018 and 2019 persisted for 286 days (at Natchez, MS). During the 2019 hydrologic year the Mississippi was overbank for a record duration of 216 days, resulting in a much greater duration of overbank sedimentation than the 2011 (53 days) and 1973 (90 days) flood events.</p><p>The thickness of overbank deposits are reported for 48 field sites across a range of depositional environments typical of large lowland meandering river floodplains. Flood deposits were sampled in October 2019 using conventional field sampling procedures, including sedimentation traps (artificial grass mats installed in October 2017) and recognition of recent sediment deposited atop buried organic layers. The thickness of each reported sample is an average of three measurements obtained at each field site.</p><p>The average thickness of flood deposit samples over 2018-2019 hydrologic years is 71 mm, with variability according to distance from channel and floodplain depositional environment. Maximum sedimentation was associated with crevasse (750 mm) and sand sheet (1,430 mm) deposition along the crest of natural levees. Sedimentation thickness decreases within ~250 m of the channel, but remains high at a distance of ~3.5 km (30 mm). Beyond the range of sand sheet deposition, overbank deposition is likely influenced by variability in floodplain hydrology and geomorphology across natural levee (181 mm), meander scroll (30 mm), old channel (77 mm), and backswamp (108 mm) environments. High backswamp sedimentation at the study site is likely influenced by historic hydraulic engineering for flood control, which has altered local sedimentation patterns.</p><p>The 2018-2019 sedimentation data are contextualized by comparison with field data from the record 2011 magnitude flood (peak Q of 65,978 m<sup>3</sup>/s at Vicksburg, MS, USGS 0728900) and the historic 1973 flood (55,558 m<sup>3</sup>/s).  Average sediment thickness for the 2011 and 1973 overbank deposits was 42 mm (n=49) and 230 mm (n=31), respectively. The 2018-2019 daily sedimentation rate (0.25 mm/day) is much less than 2011 (0.75 mm/day). Thus, the much thicker sedimentary deposits for the 2018-2019 events suggests the greater importance of flood duration – rather than flood magnitude – to overall floodplain processes and alluvial fill chronologies along lowland rivers. The much lower flood sedimentation rate for 2018-2019 in comparison with 1973 (2.49 mm/day) may reveal the persistent decline in Mississippi suspended sediment loads since the early 1950s. Study results are further contextualized by considering corresponding event-based discharge – suspended sediment dynamics, sediment province, as well as flood hydroclimatology.</p>

scholarly journals Late Holocene environmental reconstructions and their implications on flood events, typhoon, and agricultural activities in NE Taiwan

2014 ◽  
Vol 10 (5) ◽  
pp. 1857-1869 ◽  
Author(s):  
L.-C. Wang ◽  
H. Behling ◽  
T.-Q. Lee ◽  
H.-C. Li ◽  
C.-A. Huh ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Southern Oscillation ◽  
Phase 1 ◽  
Warm Pool ◽  
Ice Age ◽  
Agricultural Activities ◽  
Flood Events ◽  
Climate Conditions ◽  
Hydrological Conditions ◽  
Enso Events

Abstract. We reconstructed paleoenvironmental changes from a sediment archive of a lake in the floodplain of the Ilan Plain of NE Taiwan on multi-decadal resolution for the last ca. 1900 years. On the basis of pollen and diatom records, we evaluated past floods, typhoons, and agricultural activities in this area which are sensitive to the hydrological conditions in the western Pacific. Considering the high sedimentation rates with low microfossil preservations in our sedimentary record, multiple flood events were. identified during the period AD 100–1400. During the Little Ice Age phase 1 (LIA 1 – AD 1400–1620), the abundant occurrences of wetland plant (Cyperaceae) and diatom frustules imply less flood events under stable climate conditions in this period. Between AD 500 and 700 and the Little Ice Age phase 2 (LIA 2 – AD 1630–1850), the frequent typhoons were inferred by coarse sediments and planktonic diatoms, which represented more dynamical climate conditions than in the LIA 1. By comparing our results with the reconstructed changes in tropical hydrological conditions, we suggested that the local hydrology in NE Taiwan is strongly influenced by typhoon-triggered heavy rainfalls, which could be influenced by the variation of global temperature, the expansion of the Pacific warm pool, and the intensification of El Niño–Southern Oscillation (ENSO) events.

Methodology for risk assessment of flash flood events due to climate and land use changes

2012 ◽  
Author(s):  
M Velasco ◽  
A Cabello ◽  
I Escaler ◽  
J Barredo ◽  
A Barrera-Escoda
Keyword(s):  
Risk Assessment ◽  
Land Use ◽  
Flash Flood ◽  
Land Use Changes ◽  
Flood Events

scholarly journals SEAMUS (v1.0): a Δ<sup>14</sup>C-enabled, single-specimen sediment accumulation simulator

2019 ◽  
Author(s):  
Bryan C. Lougheed
Keyword(s):  
Sediment Core ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Species Abundance ◽  
Depth Interval ◽  
Single Specimen ◽  
14C Dating ◽  
Deep Sea Sediment ◽  
Wide Range ◽  
History Of

Abstract. The systematic bioturbation of single particles (such as foraminifera) within deep-sea sediment archives leads to the apparent smoothing of any temporal signal as record by the downcore, discrete-depth mean signal. This smoothing is the result of the systematic mixing of particles from a wide range of depositional ages into the same discrete depth interval. Previous sediment models that simulate bioturbation have specifically produced an output in the form of a downcore, discrete-depth mean signal. Palaeoceanographers analysing the distribution of single foraminifera specimens from sediment core intervals would be assisted by a model that specifically evaluates the effect of bioturbation upon single specimen populations. Taking advantage of recent increases in computer memory, the single-specimen SEdiment AccuMUlation Simulator (SEAMUS) was created in Matlab, whereby large arrays of single specimens are simulated. This simulation allows researchers to analyse the post-bioturbation age heterogeneity of single specimens contained within discrete-depth sediment core intervals, and how this heterogeneity is influenced by changes in sediment accumulation rate (SAR), bioturbation depth (BD) and species abundance. The simulation also assigns a realistic 14C activity to each specimen, by considering the dynamic Δ14C history of the Earth and temporal changes in reservoir age. This approach allows for the quantification of possible significant artefacts arising when 14C dating multi-specimen samples with heterogeneous 14C activity. Users may also assign additional desired carrier signals to specimens (e.g., stable isotopes, trace elements, temperature, etc.) and consider a second species with an independent abundance. Finally, the model can simulate a virtual palaeoceanographer by randomly picking whole specimens (whereby the user can set the percentage of older, broken specimens) of a prescribed sample size from discrete depths, after which virtual laboratory 14C dating and 14C calibration is carried out within the model.

scholarly journals Analysis of Flood Vulnerability as a Support to Water Sensitive Urban Design Planning in Klaten Regency

2021 ◽  
Vol 26 (2) ◽  
pp. 183-193
Author(s):  
Desyta Ulfiana ◽  
Yudi Eko Windarto ◽  
Nurhadi Bashit ◽  
Novia Sari Ristianti
Keyword(s):  
Land Use ◽  
Urban Design ◽  
Flood Hazard ◽  
Flood Management ◽  
Flood Vulnerability ◽  
Geological Conditions ◽  
Order Preference ◽  
Water Sensitive Urban Design ◽  
High Flood ◽  
High Level

Klaten Regency is one of the regions that has a high level of flood vulnerability. The area of Klaten Regency which is huge and has diverse characteristics makes it difficult to determine an appropriate flood management model. Water Sensitive Urban Design (WSUD) is a model that focuses on handling water management problems with environmentally friendly infrastructure. Therefore, an analysis is carried out to determine the level of flood vulnerability and factors causing flooding to plan a WSUD design that is suitable for each sub-districts of Klaten Regency. The Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods are used to help the analysis. Aspects used as criteria are rainfall, slope, soil type, geological conditions, and land use. Based on the analysis, it could be concluded that Klaten Regency has two sub-districts with high flood hazard category, 21 sub-districts with medium category, and three sub-districts with low category. Bayat and Cawas are sub-districts that have a high level of flood vulnerability category. Meanwhile, Kemalang, Karangnongko and Polanharjo are districts with a low level of flood vulnerability category. The main factors causing flooding in Klaten Regency are slope and land use.

scholarly journals Enhanced Moisture Delivery into Victoria Land, East Antarctica During the Early Last Interglacial: Implications for West Antarctic Ice Sheet Stability

2021 ◽  
Author(s):  
Yuzhen Yan ◽  
Nicole E. Spaulding ◽  
Michael L. Bender ◽  
Edward J. Brook ◽  
John A. Higgins ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Cores ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Ice Age ◽  
Accumulation Rates ◽  
Last Interglacial ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Victoria Land

Abstract. The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in Southern Victoria Land ~80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate of S27 covering the Last Interglacial (LIG) period between 129 and 116 thousand years before present (ka) to infer moisture transport into the region. The accumulation rate is based on the ice age-gas age differences calculated from the ice chronology, which is constrained by the stable water isotopes of the ice, and an improved gas chronology based on measurements of oxygen isotopes of O2 in the trapped gases. The peak accumulation rate in S27 occurred at 128.2 ka, near the peak LIG warming in Antarctica. Even the most conservative estimate yields a six-fold increase in the accumulation rate in the LIG, whereas other Antarctic ice cores are typically characterized by a glacial-interglacial difference of a factor of two to three. While part of the increase in S27 accumulation rates must originate from changes in the large-scale atmospheric circulation, additional mechanisms are needed to explain the large changes. We hypothesize that the exceptionally high snow accumulation recorded in S27 reflects open-ocean conditions in the Ross Sea, created by reduced sea ice extent and increased polynya size, and perhaps by a southward retreat of the Ross Ice Shelf relative to its present-day position near the onset of LIG. The proposed ice shelf retreat would also be compatible with a sea-level high stand around 129 ka significantly sourced from West Antarctica. The peak in S27 accumulation rates is transient, suggesting that if the Ross Ice Shelf had indeed retreated during the early LIG, it would have re-advanced by 125 ka.

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