scholarly journals On the magnitude and frequency of Karakoram Glacier surges

2013 ◽  
Vol 7 (5) ◽  
pp. 5177-5187
Author(s):  
D. J. Quincey ◽  
A. Luckman
Keyword(s):  
Mass Balance ◽  
Return Period ◽  
Accurate Mass ◽  
Return Periods ◽  
Present Evidence ◽  
Surface Displacements ◽  
Hindu Kush ◽  
Glacier Surges

Abstract. The return periods of Karakoram glacier surges are almost entirely unknown. Here, we present evidence of an historic surge of the Khurdopin Glacier that began in the mid-1970s and peaked in 1979. Measured surface displacements reached > 5 km yr–1, two orders of magnitude faster than during quiescence and twice as large as any previously recorded velocity in the region. The Khurdopin Glacier next surged in the late-1990s, equating to a return period of 20 yr. Surge activity in the region needs to be better understood if accurate mass balance assessments of Hindu-Kush–Karakoram–Himalaya glaciers are to be made.

scholarly journals Brief Communication: On the magnitude and frequency of Khurdopin glacier surge events

2014 ◽  
Vol 8 (2) ◽  
pp. 571-574 ◽  
Author(s):  
D. J. Quincey ◽  
A. Luckman
Keyword(s):  
Mass Balance ◽  
Return Period ◽  
Accurate Mass ◽  
Return Periods ◽  
Present Evidence ◽  
Remarkable Similarity ◽  
Surface Displacements ◽  
Hindu Kush ◽  
Glacier Surges

Abstract. The return periods of Karakoram glacier surges are poorly quantified. Here, we present evidence of an historic surge of the Khurdopin Glacier that began in the mid-1970s and peaked in 1979. Measured surface displacements reached >5 km a−1, two orders of magnitude faster than during quiescence. The Khurdopin Glacier next surged in the late 1990s, equating to a return period of 20 years. Surge evolution in the two events shows remarkable similarity suggesting a common trigger. Surge activity in the Karakoram needs to be better understood if accurate mass balance assessments of Hindu-Kush–Karakoram–Himalaya glaciers are to be made.

scholarly journals Joint return periods in hydrology: a critical and practical review focusing on synthetic design hydrograph estimation

2012 ◽  
Vol 9 (5) ◽  
pp. 6781-6828 ◽  
Author(s):  
S. Vandenberghe ◽  
M. J. van den Berg ◽  
B. Gräler ◽  
A. Petroselli ◽  
S. Grimaldi ◽  
...  
Keyword(s):  
Frequency Analysis ◽  
Return Period ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Return Periods ◽  
Design Variables ◽  
Joint Return ◽  
Design Values ◽  
Multivariate Frequency Analysis ◽  
Joint Return Period

Abstract. Most of the hydrological and hydraulic studies refer to the notion of a return period to quantify design variables. When dealing with multiple design variables, the well-known univariate statistical analysis is no longer satisfactory and several issues challenge the practitioner. How should one incorporate the dependence between variables? How should the joint return period be defined and applied? In this study, an overview of the state-of-the-art for defining joint return periods is given. The construction of multivariate distribution functions is done through the use of copulas, given their practicality in multivariate frequency analysis and their ability to model numerous types of dependence structures in a flexible way. A case study focusing on the selection of design hydrograph characteristics is presented and the design values of a three-dimensional phenomenon composed of peak discharge, volume and duration are derived. Joint return period methods based on regression analysis, bivariate conditional distributions, bivariate joint distributions, and Kendal distribution functions are investigated and compared highlighting theoretical and practical issues of multivariate frequency analysis. Also an ensemble-based method is introduced. For a given design return period, the method chosen clearly affects the calculated design event. Eventually, light is shed on the practical implications of a chosen method.

scholarly journals Global flood hazard map and exposed GDP comparison: a China case study

2020 ◽  
Author(s):  
Jerom P. M. Aerts ◽  
Steffi Uhlemann-Elmer ◽  
Dirk Eilander ◽  
Philip J. Ward
Keyword(s):  
Return Period ◽  
Flood Hazard ◽  
Regional Scale ◽  
Flood Protection ◽  
Economic Losses ◽  
Return Periods ◽  
Hazard Maps ◽  
High Exposure ◽  
Pluvial Flooding

Abstract. Floods are among the most frequent and damaging natural hazard events in the world. In 2016, economic losses from flooding amounted to $56 bn globally, of which $20 bn occurred in China (Munich Re, 2017). National or regional scale mapping of flood hazard is at present providing an inconsistent and incomplete picture of floods. Over the past decade global flood hazard models have been developed and continuously improved. There is now a significant demand for testing of the global hazard maps generated by these models in order to understand their applicability for international risk reduction strategies and for reinsurance portfolio risk assessments using catastrophe models. We expand on existing methods for comparing global hazard maps and analyse 8 global flood models (GFMs) that represent the current state of the global flood modelling community. We apply our comparison to China as a case study and, for the first time, we include industry models, pluvial flooding, and flood protection standards in the analysis. We find substantial variability between the flood hazard maps in modelled inundated area and exposed GDP across multiple return periods (ranging from 5 to 1500 years) and in expected annual exposed GDP. For example, for the 100 year return period undefended (assuming no flood protection) hazard maps the percentage of total affected GDP of China ranges between 4.4 % and 10.5 % for fluvial floods. For the majority of the GFMs we see only a small increase in inundated area or exposed GDP for high return period undefended hazard maps compared to low return periods, highlighting major limitations in the models’ resolution and their output. The inclusion of industry models which currently model flooding at higher spatial resolution, and which additionally include pluvial flooding, strongly improves the comparison and provides important new benchmarks. Pluvial flooding can increase the expected annual exposed GDP by as much as 1.3 % points. Our study strongly highlights the importance of flood defenses for a realistic risk assessment in countries like China that are characterized by high concentrations of exposure. Even an incomplete (1.74 % of area of China) but locally detailed layer of structural defenses in high exposure areas reduces the expected annual exposed GDP to fluvial and pluvial flooding from 4.1 % to 2.8 %.

scholarly journals Extremeness of recent drought events in Switzerland: dependence on variable and return period choice

2019 ◽  
Vol 19 (10) ◽  
pp. 2311-2323 ◽  
Author(s):  
Manuela I. Brunner ◽  
Katharina Liechti ◽  
Massimiliano Zappa
Keyword(s):  
Soil Moisture ◽  
Frequency Analysis ◽  
Return Period ◽  
Threshold Level ◽  
Low Flow ◽  
Drought Event ◽  
Return Periods ◽  
Event Identification ◽  
Groundwater Drought ◽  
Drought Frequency Analysis

Abstract. The 2018 drought event had severe ecological, economic, and social impacts. How extreme was it in Switzerland? We addressed this question by looking at different types of drought, including meteorological, hydrological, agricultural, and groundwater drought, and at the two characteristics deficit and deficit duration. The analysis consisted of three main steps: (1) event identification using a threshold-level approach, (2) drought frequency analysis, and (3) comparison of the 2018 event to the severe 2003 and 2015 events. In Step 2 the variables precipitation, discharge, soil moisture, and low-flow storage were first considered separately in a univariate frequency analysis; pairs of variables were then investigated jointly in a bivariate frequency analysis using a copula model for expressing the dependence between the two variables under consideration. Our results show that the 2018 event was especially severe in north-eastern Switzerland in terms of soil moisture, with return periods locally exceeding 100 years. Slightly longer return periods were estimated when discharge and soil moisture deficits were considered together. The return period estimates depended on the region, variable, and return period considered. A single answer to the question of how extreme the 2018 drought event was in Switzerland is therefore not possible – rather, it depends on the processes one is interested in.

scholarly journals On the role of the runoff coefficient in the mapping of rainfall to flood return periods

2009 ◽  
Vol 13 (5) ◽  
pp. 577-593 ◽  
Author(s):  
A. Viglione ◽  
R. Merz ◽  
G. Blöschl
Keyword(s):  
Monte Carlo ◽  
Return Period ◽  
Threshold Effect ◽  
Flood Frequency ◽  
Runoff Coefficient ◽  
Return Periods ◽  
Runoff Generation ◽  
Design Storm ◽  
Shed Light

Abstract. While the correspondence of rainfall return period TP and flood return period TQ is at the heart of the design storm procedure, their relationship is still poorly understood. The purpose of this paper is to shed light on the controls on this relationship examining in particular the effect of the variability of event runoff coefficients. A simplified world with block rainfall and linear catchment response is assumed and a derived flood frequency approach, both in analytical and Monte-Carlo modes, is used. The results indicate that TQ can be much higher than TP of the associated storm. The ratio TQ /TP depends on the average wetness of the system. In a dry system, TQ can be of the order of hundreds of times of TP. In contrast, in a wet system, the maximum flood return period is never more than a few times that of the corresponding storm. This is because a wet system cannot be much worse than it normally is. The presence of a threshold effect in runoff generation related to storm volume reduces the maximum ratio of TQ /TP since it decreases the randomness of the runoff coefficients and increases the probability to be in a wet situation. We also examine the relation between the return periods of the input and the output of the design storm procedure when using a pre-selected runoff coefficient and the question which runoff coefficients produce a flood return period equal to the rainfall return period. For the systems analysed here, this runoff coefficient is always larger than the median of the runoff coefficients that cause the maximum annual floods. It depends on the average wetness of the system and on the return period considered, and its variability is particularly high when a threshold effect in runoff generation is present.

Mass balance change as a control on the frequency and occurrence of glacier surges in Svalbard, Norwegian High Arctic

1995 ◽  
Vol 22 (21) ◽  
pp. 2909-2912 ◽  
Author(s):  
J. A. Dowdeswell ◽  
R. Hodgkins ◽  
A.-M. Nuttall ◽  
J. O. Hagen ◽  
G. S. Hamilton
Keyword(s):  
Mass Balance ◽  
High Arctic ◽  
Glacier Surges

scholarly journals Hazard from Himalayan glacier lake outburst floods

2019 ◽  
Vol 117 (2) ◽  
pp. 907-912 ◽  
Author(s):  
Georg Veh ◽  
Oliver Korup ◽  
Ariane Walz
Keyword(s):  
Western Himalayas ◽  
Return Periods ◽  
Outburst Flood ◽  
Average Volume ◽  
Eastern Himalayas ◽  
Outburst Floods ◽  
Hindu Kush ◽  
Order Of Magnitude ◽  
Highest Density Interval ◽  
Increasing Trends

Sustained glacier melt in the Himalayas has gradually spawned more than 5,000 glacier lakes that are dammed by potentially unstable moraines. When such dams break, glacier lake outburst floods (GLOFs) can cause catastrophic societal and geomorphic impacts. We present a robust probabilistic estimate of average GLOFs return periods in the Himalayan region, drawing on 5.4 billion simulations. We find that the 100-y outburst flood has an average volume of 33.5+3.7/−3.7 × 106 m3 (posterior mean and 95% highest density interval [HDI]) with a peak discharge of 15,600+2,000/−1,800 m3⋅s−1. Our estimated GLOF hazard is tied to the rate of historic lake outbursts and the number of present lakes, which both are highest in the Eastern Himalayas. There, the estimated 100-y GLOF discharge (∼14,500 m3⋅s−1) is more than 3 times that of the adjacent Nyainqentanglha Mountains, and at least an order of magnitude higher than in the Hindu Kush, Karakoram, and Western Himalayas. The GLOF hazard may increase in these regions that currently have large glaciers, but few lakes, if future projected ice loss generates more unstable moraine-dammed lakes than we recognize today. Flood peaks from GLOFs mostly attenuate within Himalayan headwaters, but can rival monsoon-fed discharges in major rivers hundreds to thousands of kilometers downstream. Projections of future hazard from meteorological floods need to account for the extreme runoffs during lake outbursts, given the increasing trends in population, infrastructure, and hydropower projects in Himalayan headwaters.

Spatial analysis of return periods of hydrological drought of Nile River Basin

2020 ◽  
Author(s):  
Gizaw Mengistu Tsidu
Keyword(s):  
River Basin ◽  
Water Resource ◽  
Return Period ◽  
Arrival Time ◽  
Population Increase ◽  
Drought Severity ◽  
Nile River ◽  
Return Periods ◽  
The Mean ◽  
Nile River Basin

<p>The Nile River Basin has been vital source of water to Riparian countries in both upper and lower catchments of the Basin. However, the states in the lower catchment namely Sudan and Egypt have exploited this resource without significant competition from countries in the upper catchments in the past. Recently, due to population increase in the basin and climate change, there are some initiatives by Riparian States such as Ethiopia to use this vital water resource (e.g., for energy generation). Therefore, it is important to understand recurrent drought characteristics and its potential impacts on the water resource in the basin. Drought events in the Nile Basin have been extracted using run theory based on the Standardized Precipitation Evapotranspiration Index (SPEI) accumulated on the time scale of 12 months using CRU rainfall and evapotranspiration data, which covers the period 1901–2018. The drought events are characterized by four variables: duration, severity. Intensity and Inter-arrival time. The mean duration and severity of drought during the last 118 years over the Basin are generally short and moderate over upper catchments. Conversely, the mean duration various from 4 to 8 months and up to 14 months over the middle and lower catchments of the Basin respectively while the mean drought severity increases from -2 at upper catchment to -7 at lower catchment. Gamma, Weibull, Gamma and Exponential functions are then selected to describe the marginal distribution of severity, duration, intensity and inter-arrival time, respectively. The Gumbel–Hougaard Copula was used to construct the joint distribution of duration, severity, intensity and/or inter-arrival time. The results indicate that the return period is dependent on the location within the basin, variable type and the combination of variables. For extreme droughts with severity index of -10 and duration of 14 months, return periods are longer than 40 years over south parts of the Basin and it barely exceeds 25 years over northern parts of the Basin. Generally, the short return period is mainly distributed in lower catchments of the Basin. This study on the identification of spatial distributions of drought return periods across the Basin is therefore important for drought mitigation and strategic planning on the water resource.</p>

scholarly journals Modelling and assessment of urban flood hazards based on rainfall intensity-duration-frequency curves reformation

2016 ◽  
Author(s):  
Reza Ghazavi ◽  
Ali Moafi Rabori ◽  
Mohsen Ahadnejad Reveshty
Keyword(s):  
Return Period ◽  
Urban Areas ◽  
Rainfall Intensity ◽  
Flood Hazards ◽  
Return Periods ◽  
Urban Flood ◽  
Design Storm ◽  
Hourly Rainfall ◽  
Idf Curves ◽  
Intensity Duration Frequency

Abstract. Estimate design storm based on rainfall intensity–duration–frequency (IDF) curves is an important parameter for hydrologic planning of urban areas. The main aim of this study was to estimate rainfall intensities of Zanjan city watershed based on overall relationship of rainfall IDF curves and appropriate model of hourly rainfall estimation (Sherman method, Ghahreman and Abkhezr method). Hydrologic and hydraulic impacts of rainfall IDF curves change in flood properties was evaluated via Stormwater Management Model (SWMM). The accuracy of model simulations was confirmed based on the results of calibration. Design hyetographs in different return periods show that estimated rainfall depth via Sherman method are greater than other method except for 2-year return period. According to Ghahreman and Abkhezr method, decrease of runoff peak was 30, 39, 41 and 42 percent for 5-10-20 and 50-year return periods respectively, while runoff peak for 2-year return period was increased by 20 percent.

scholarly journals Tributary glacier surges: an exceptional concentration at Panmah Glacier, Karakoram Himalaya

2007 ◽  
Vol 53 (181) ◽  
pp. 181-188 ◽  
Author(s):  
Kenneth Hewitt
Keyword(s):  
High Altitude ◽  
Mass Balance ◽  
Regional Climate ◽  
High Altitudes ◽  
Short Term ◽  
Thermal Regimes ◽  
Glacier Surges ◽  
Comparable Period

AbstractFour tributaries of Panmah Glacier have surged in less than a decade, three in quick succession between 2001 and 2005. Since 1985, 13 surges have been recorded in the Karakoram Himalaya, more than in any comparable period since the 1850s. Ten were tributary surges. In these ten a full run-out of surge ice is prevented, but extended post-surge episodes affect the tributary and main glacier. The sudden concentration of events at Panmah Glacier is without precedent and at odds with known surge intervals for the glaciers. Interpretations must consider the response of thermally complex glaciers, at exceptionally high altitudes and of high relief, to changes in a distinctive regional climate. It is suggested that high-altitude warming affecting snow and glacier thermal regimes, or bringing intense, short-term melting episodes, may be more significant than mass-balance change.

Sign in / Sign up

Export Citation Format

Share Document