scholarly journals Effects of glacier retreat on the outbursts of Goësvatnet, southwest Spitsbergen, Svalbard

1997 ◽  
Vol 43 (144) ◽  
pp. 276-282 ◽  
Author(s):  
W. Schöner ◽  
M. Schöner
Keyword(s):  
Regression Equation ◽  
Peak Discharge ◽  
Glacier Retreat ◽  
Original Form ◽  
Volume Data ◽  
Discharge Data ◽  
Lake Volume ◽  
Outburst Floods ◽  
Peak Discharges ◽  
Progressive Enlargement

AbstractEffects of the retreat of Gåsbreen, southwest Spitsbergen, Svalbard, on the evolution of the ice-dammed lake Goësvatnet are shown for the period 1899-1991. The retreat and lowering of the damming ice masses have changed not only the stored lake volume, the lake geometry and the elevation, slope and length of the subglacial outlet tunnel, but also the frequency and magnitude of outburst floods of Goësvatnet. For the estimation of peak discharges of outburst floods we computed an unbiased regression equation related to the progressive enlargement of subglacial tunnels using lake volume data and peak discharge data from the literature. The derived equation is very similar to the original form of the Clague-Mathews formula and answers the question why this formula has worked well in many cases. Peak discharges of Goësvatnet in various years were estimated by means of the derived equation. Effects of the changed lake geometry as well as the changed length and slope of the subglacial outlet tunnel on the discharge during outbursts will be discussed by means of the Nye-Clarke model. Observation of an outburst of Goësvatnet in summer 1991 indicates that the outbursts may have been triggered by pressure decrease in the subglacial outlet tunnel during increased discharge, whereas flotation of the ice dam can be excluded.

scholarly journals Effects of glacier retreat on the outbursts of Goësvatnet, southwest Spitsbergen, Svalbard

1997 ◽  
Vol 43 (144) ◽  
pp. 276-282 ◽  
Author(s):  
W. Schöner ◽  
M. Schöner
Keyword(s):  
Regression Equation ◽  
Peak Discharge ◽  
Glacier Retreat ◽  
Original Form ◽  
Volume Data ◽  
Discharge Data ◽  
Lake Volume ◽  
Outburst Floods ◽  
Peak Discharges ◽  
Progressive Enlargement

AbstractEffects of the retreat of Gåsbreen, southwest Spitsbergen, Svalbard, on the evolution of the ice-dammed lake Goësvatnet are shown for the period 1899-1991. The retreat and lowering of the damming ice masses have changed not only the stored lake volume, the lake geometry and the elevation, slope and length of the subglacial outlet tunnel, but also the frequency and magnitude of outburst floods of Goësvatnet. For the estimation of peak discharges of outburst floods we computed an unbiased regression equation related to the progressive enlargement of subglacial tunnels using lake volume data and peak discharge data from the literature. The derived equation is very similar to the original form of the Clague-Mathews formula and answers the question why this formula has worked well in many cases. Peak discharges of Goësvatnet in various years were estimated by means of the derived equation. Effects of the changed lake geometry as well as the changed length and slope of the subglacial outlet tunnel on the discharge during outbursts will be discussed by means of the Nye-Clarke model. Observation of an outburst of Goësvatnet in summer 1991 indicates that the outbursts may have been triggered by pressure decrease in the subglacial outlet tunnel during increased discharge, whereas flotation of the ice dam can be excluded.

Glacier Retreat and Glacial Lake Outburst Floods (GLOFs)

2017 ◽  
Author(s):  
Adam Emmer
Keyword(s):  
Climate Change ◽  
Slope Movement ◽  
Glacier Retreat ◽  
Dam Failure ◽  
Glacial Lake ◽  
Human Society ◽  
Slope Movements ◽  
Continental Scale ◽  
Outburst Floods ◽  
Peak Discharges

Glacier retreat is considered to be one of the most obvious manifestations of recent and ongoing climate change in the majority of glacierized alpine and high-latitude regions throughout the world. Glacier retreat itself is both directly and indirectly connected to the various interrelated geomorphological/hydrological processes and changes in hydrological regimes. Various types of slope movements and the formation and evolution of lakes are observed in recently deglaciated areas. These are most commonly glacial lakes (ice-dammed, bedrock-dammed, or moraine-dammed lakes). “Glacial lake outburst flood” (GLOF) is a phrase used to describe a sudden release of a significant amount of water retained in a glacial lake, irrespective of the cause. GLOFs are characterized by extreme peak discharges, often several times in excess of the maximum discharges of hydrometeorologically induced floods, with an exceptional erosion/transport potential; therefore, they can turn into flow-type movements (e.g., GLOF-induced debris flows). Some of the Late Pleistocene lake outburst floods are ranked among the largest reconstructed floods, with peak discharges of up to 107 m3/s and significant continental-scale geomorphic impacts. They are also considered capable of influencing global climate by releasing extremely high amounts of cold freshwater into the ocean. Lake outburst floods associated with recent (i.e., post-Little Ice Age) glacier retreat have become a widely studied topic from the perspective of the hazards and risks they pose to human society, and the possibility that they are driven by anthropogenic climate change. Despite apparent regional differences in triggers (causes) and subsequent mechanisms of lake outburst floods, rapid slope movement into lakes, producing displacement waves leading to dam overtopping and eventually dam failure, is documented most frequently, being directly (ice avalanche) and indirectly (slope movement in recently deglaciated areas) related to glacial activity and glacier retreat. Glacier retreat and the occurrence of GLOFs are, therefore, closely tied, because glacier retreat is connected to: (a) the formation of new, and the evolution of existing, lakes; and (b) triggers of lake outburst floods (slope movements).

scholarly journals Estimates of Peak Discharge from the Drainage of Ice-Dammed Ape Lake, British Columbia, Canada

1989 ◽  
Vol 35 (121) ◽  
pp. 349-354 ◽  
Author(s):  
Joseph R. Desloges ◽  
David P. Jones ◽  
Karl E. Ricker
Keyword(s):  
British Columbia ◽  
Flood Plain ◽  
Peak Discharge ◽  
Outburst Flood ◽  
Flood Peak ◽  
Lake Volume ◽  
Outburst Floods ◽  
Direct Measurements ◽  
Instantaneous Discharge ◽  
Method Yield

AbstractThe first known occurrence of outburst flooding at Ape Lake, British Columbia, was in October 1984 following the formation of a subglacial tunnel in an ice dam created by Fyles Glacier. Following tunnel closure, the lake refilled in 150 d and then a second outburst flood occurred in August 1986. During both events, 55% of the Apc Lake volume or 46 × 106m3was released in less than 24 h into the 50 km long, ungauged Noeick River, producing an average discharge of 540 m3s−1. Channel and flood-plain erosion, damage to access roads, bridges, a logging camp, and an airstrip were related to the peak or maximum instantaneous discharge. In the absence of direct measurements, and to facilitate planning for future flood events, several independent methods were employed to estimate peak discharge. A modified version of the Clague-Mathews formula and the slope-area method yield consistent estimates which approach 1600 m3s−1near the ice-dam outlet. Attenuation of the flood peak in Noeick River is as high as 25% in the upper 12 km due to channel and flood-plain storage. Results using Clarke’s (1982) physical-based model suggest lower discharges and may be related to the irregular morphology of Ape Lake. Since Fyles Glacier is in continuous retreat, drainage around the margin of the ice dam which began in the summer of 1987 is expected to continue and no further outburst floods are anticipated.

scholarly journals Estimates of Peak Discharge from the Drainage of Ice-Dammed Ape Lake, British Columbia, Canada

1989 ◽  
Vol 35 (121) ◽  
pp. 349-354 ◽  
Author(s):  
Joseph R. Desloges ◽  
David P. Jones ◽  
Karl E. Ricker
Keyword(s):  
British Columbia ◽  
Flood Plain ◽  
Peak Discharge ◽  
Outburst Flood ◽  
Flood Peak ◽  
Lake Volume ◽  
Outburst Floods ◽  
Direct Measurements ◽  
Instantaneous Discharge ◽  
Method Yield

AbstractThe first known occurrence of outburst flooding at Ape Lake, British Columbia, was in October 1984 following the formation of a subglacial tunnel in an ice dam created by Fyles Glacier. Following tunnel closure, the lake refilled in 150 d and then a second outburst flood occurred in August 1986. During both events, 55% of the Apc Lake volume or 46 × 106 m3 was released in less than 24 h into the 50 km long, ungauged Noeick River, producing an average discharge of 540 m3 s−1. Channel and flood-plain erosion, damage to access roads, bridges, a logging camp, and an airstrip were related to the peak or maximum instantaneous discharge. In the absence of direct measurements, and to facilitate planning for future flood events, several independent methods were employed to estimate peak discharge. A modified version of the Clague-Mathews formula and the slope-area method yield consistent estimates which approach 1600 m3 s−1 near the ice-dam outlet. Attenuation of the flood peak in Noeick River is as high as 25% in the upper 12 km due to channel and flood-plain storage. Results using Clarke’s (1982) physical-based model suggest lower discharges and may be related to the irregular morphology of Ape Lake. Since Fyles Glacier is in continuous retreat, drainage around the margin of the ice dam which began in the summer of 1987 is expected to continue and no further outburst floods are anticipated.

scholarly journals Estimation of Peak Discharge Quantiles for Selected Annual Exceedance Probabilities in Northeastern Illinois

2016 ◽  
Author(s):  
Thomas Over ◽  
◽  
Riki Saito ◽  
Andrea Veilleux ◽  
Padraic O’Shea ◽  
...  
Keyword(s):  
Spatial Analysis ◽  
Least Squares ◽  
Drainage Basin ◽  
Peak Discharge ◽  
Regression Equations ◽  
Annual Maximum ◽  
Discharge Data ◽  
Maximum Peak ◽  
Quantile Estimates ◽  
Peak Discharges

This report provides two sets of equations for estimating peak discharge quantiles at annual exceedance probabilities (AEPs) of 0.50, 0.20, 0.10, 0.04, 0.02, 0.01, 0.005, and 0.002 (recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively) for watersheds in Illinois based on annual maximum peak discharge data from 117 watersheds in and near northeastern Illinois. One set of equations was developed through a temporal analysis with a two-step least squares-quantile regression technique that measures the average effect of changes in the urbanization of the watersheds used in the study. The resulting equations can be used to adjust rural peak discharge quantiles for the effect of urbanization, and in this study the equations also were used to adjust the annual maximum peak discharges from the study watersheds to 2010 urbanization conditions. The other set of equations was developed by a spatial analysis. This analysis used generalized least-squares regression to fit the peak discharge quantiles computed from the urbanization-adjusted annual maximum peak discharges from the study watersheds to drainage-basin characteristics. The peak discharge quantiles were computed by using the Expected Moments Algorithm following the removal of potentially influential low floods defined by a multiple Grubbs-Beck test. To improve the quantile estimates, regional skew coefficients were obtained from a newly developed regional skew model in which the skew increases with the urbanized land use fraction. The skew coefficient values for each streamgage were then computed as the variance-weighted average of at-site and regional skew coefficients. The drainage-basin characteristics used as explanatory variables in the spatial analysis include drainage area, the fraction of developed land, the fraction of land with poorly drained soils or likely water, and the basin slope estimated as the ratio of the basin relief to basin perimeter. This report also provides: (1) examples to illustrate the use of the spatial and urbanization-adjustment equations for estimating peak discharge quantiles at ungaged sites and to improve flood-quantile estimates at and near a gaged site; (2) the urbanization-adjusted annual maximum peak discharges and peak discharge quantile estimates at streamgages from 181 watersheds including the 117 study watersheds and 64 additional watersheds in the study region that were originally considered for use in the study but later deemed to be redundant. The urbanization-adjustment equations, spatial regression equations, and peak discharge quantile estimates developed in this study will be made available in the web-based application StreamStats, which provides automated regression-equation solutions for user-selected stream locations. Figures and tables comparing the observed and urbanization-adjusted peak discharge records by streamgage are provided at http://dx.doi.org/10.3133/sir20165050 for download.

scholarly journals Benefits and limitations of data assimilation for discharge forecasting using an event-based rainfall–runoff model

2013 ◽  
Vol 13 (3) ◽  
pp. 583-596 ◽  
Author(s):  
M. Coustau ◽  
S. Ricci ◽  
V. Borrell-Estupina ◽  
C. Bouvier ◽  
O. Thual
Keyword(s):  
Data Assimilation ◽  
Hydrological Model ◽  
Peak Discharge ◽  
State Variables ◽  
Rainfall Runoff ◽  
Discharge Data ◽  
Southern France ◽  
Flood Peak ◽  
Event Based ◽  
The Impact

Abstract. Mediterranean catchments in southern France are threatened by potentially devastating fast floods which are difficult to anticipate. In order to improve the skill of rainfall-runoff models in predicting such flash floods, hydrologists use data assimilation techniques to provide real-time updates of the model using observational data. This approach seeks to reduce the uncertainties present in different components of the hydrological model (forcing, parameters or state variables) in order to minimize the error in simulated discharges. This article presents a data assimilation procedure, the best linear unbiased estimator (BLUE), used with the goal of improving the peak discharge predictions generated by an event-based hydrological model Soil Conservation Service lag and route (SCS-LR). For a given prediction date, selected model inputs are corrected by assimilating discharge data observed at the basin outlet. This study is conducted on the Lez Mediterranean basin in southern France. The key objectives of this article are (i) to select the parameter(s) which allow for the most efficient and reliable correction of the simulated discharges, (ii) to demonstrate the impact of the correction of the initial condition upon simulated discharges, and (iii) to identify and understand conditions in which this technique fails to improve the forecast skill. The correction of the initial moisture deficit of the soil reservoir proves to be the most efficient control parameter for adjusting the peak discharge. Using data assimilation, this correction leads to an average of 12% improvement in the flood peak magnitude forecast in 75% of cases. The investigation of the other 25% of cases points out a number of precautions for the appropriate use of this data assimilation procedure.

A global inventory of potential future glacial lakes

2021 ◽  
Author(s):  
Louis Frey ◽  
Holger Frey ◽  
Matthias Huss ◽  
Simon Allen ◽  
Daniel Farinotti ◽  
...  
Keyword(s):  
Water Resource Management ◽  
Routing Algorithm ◽  
Total Surface Area ◽  
Glacier Retreat ◽  
Glacial Lakes ◽  
Rcp Scenarios ◽  
First Order ◽  
Lake Volume ◽  
Lake Formation ◽  
Global Inventory

<p>A prominent phenomenon accompanying glacier retreat is the formation of new lakes. Such glacial lakes are the subject of numerous studies and investigations due to their potential to produce far-reaching glacial lake outburst floods (GLOFs), but also because they might provide opportunities for water resource management and energy production. Here we present a first global inventory of potential future glacial lakes, along with expected formation times under different RCP scenarios.</p><p>From published datasets of ice thickness distributions of all glaciers of the world, we identified glacier bed overdeepenings and extracted parameters of potential future lakes, such as area, depth and volume. The consideration of the ensemble of ice thicknesses allowed for a first-order quantification of uncertainties. We identified 67,000 (ranging from 55,000 to 87,000) overdeepenings with volumes larger than 1 x 10<sup>6</sup> m<sup>3</sup>, the total surface area and volume of corresponding potential lakes is 61,000 (56,000 to 64,000) km<sup>2</sup> and 4,600 (3,100 to 7,200) km<sup>3</sup>, respectively. However, these numbers are based on the assumption of fully water-filled overdeepenings and therefore represent upper bound estimates. Global results are strongly influenced by very large depressions identified beneath (flat) polar glaciers and ice caps.  We then combined potential future lake sites with estimated future glacier extents from a global glacier evolution model (GloGEM), in order to estimate formation periods of these future lakes, considering different RCPs. Strong regional differences are also found in the anticipated formation periods: While in the low latitudes most future lakes are expected to form in the current decade, irrespective of the RCP, Arctic regions have highest lake formation rates towards the end of the 21<sup>st</sup> century, with the majority of bed overdeepening not being exposed by glacier retreat until 2100. In mid latitude mountain regions, large differences between RCP2.6 and RCP8.5 exist in regard of the timing of lake formation and the amount of total uncovered overdeepenings.</p><p>In addition to geometric properties and expected formation periods, the topographic potential for impacting mass movements, such as rock or ice avalanches, is determined for each overdeepening. In combination with potential lake volume and watershed area of the lake, these characteristics can be used for a first order estimation of lake outburst susceptibility. With a basic flow routing algorithm, potential outburst trajectories are modeled for each overdeepening. In combination with information on population density, settlements and further socio-economic and environmental datasets, this information can be used for future analyses of hazards, risks and opportunities associated with these potential future glacial lakes.</p>

Evolving hazards from Himalayan glacier lake outburst floods

2020 ◽  
Author(s):  
Georg Veh ◽  
Daniel Garcia-Castellano ◽  
Oliver Korup
Keyword(s):  
Western Himalaya ◽  
Peak Discharge ◽  
Lake Area ◽  
Landsat Images ◽  
The Past ◽  
Himalayan Glacier ◽  
Outburst Floods ◽  
Multi Temporal ◽  
Extreme Value Model ◽  
Lake Size

<p>The ongoing retreat of glaciers has formed several thousands of meltwater lakes in the Himalayas. Hundreds of these lakes have grown rapidly in area and volume in past decades, raising widely publicised concerns of an increasing hazard from sudden glacier lake outburst floods (GLOFs). Some 40 catastrophic lake outbursts have claimed thousands of fatalities and high losses in the Himalayas, mostly as a consequence of moraine-dam failures. Human and public safety along densely populated river reaches may thus be prone to changes in the lake size-distribution and the frequency of outburst floods. Yet multi-temporal inventories of Himalayan glacier lakes and associated outburst floods that we need for hazard appraisals have been collated only for selected basins with few standardised rules. Objectively tracing changes in regional GLOF hazard through time has thus remained elusive.</p><p>Here we meet this urgent demand for an improved GLOF hazard assessment. We estimate changes in the 100-year GLOF peak discharge from the late 1980s towards a scenario of completely ice-free Himalayas. We use a Random Forest model to predict land cover from seasonal Landsat images, and automatically extract glacier lakes for four time intervals. We obtain credible lake depths and volumes for each interval from a linear model learned from published bathymetric surveys. We further project possible sites for future Himalayan meltwater lakes from three published models of subglacial topography. We assume that these presently ice-covered depressions could fill completely with water though sediment and debris could decrease the storage space for future lakes. We simulate distributions of peak discharge for historic, present, and future lakes, accounting for different combinations of lake area, breach depth, and dam lithology. Most barrier types are unknown and could range from intact metamorphic bedrock to unconsolidated moraine debris. These two end members help to constrain the physically possible boundaries of GLOF peak discharges, which is supported by data from 82 natural dam breaks with known values of erodibility. To estimate the return periods of outburst floods, we used an extreme-value model to couple our simulations of peak discharge with mean annual rates of outburst floods, which remained unchanged in the Himalayas in the past three decades.</p><p>Given this constant rate of outburst floods, we report how hazard—expressed as the 100-year GLOF discharge—varied with regionally changing lake-size distributions in the past decades. We show that the southern Himalayas of Nepal and Bhutan had the largest increase of lake area, feeding notions of a rising GLOF hazard in this region. Hazard in the Western Himalaya, Karakoram, and Hindu Kush increased marginally, in line with the smallest historic abundance of glacier lakes and outburst floods. Future lake abundance and volumes may increase at least six-fold, with the largest lakes appearing in regions that have large glaciers today such as the Western Himalaya and the Karakoram. All other controls held constant, we find that hazard from these future lakes will largely rest on the erodibility of the barrier type, which needs to be acknowledged better in hazard appraisals.</p>

Recent catastrophic landslide lake outburst floods in the Himalayan mountain range

2016 ◽  
Vol 41 (1) ◽  
pp. 3-28 ◽  
Author(s):  
Virginia Ruiz-Villanueva ◽  
Simon Allen ◽  
Manohar Arora ◽  
Narendra K Goel ◽  
Markus Stoffel
Keyword(s):  
Large Scale ◽  
Drainage System ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Remotely Sensed Data ◽  
Discharge Data ◽  
Outburst Floods ◽  
High Resolution Satellite Images ◽  
Hydrometeorological Conditions ◽  
Landslide Lake

Among the more complex and devastating interactions between climate and hydromorphological processes in mountain environments are landslide lake outburst floods (LLOFs), resulting from mass movements temporarily blocking a drainage system. This work reviews these processes in the Himalayas and highlights the high frequency of this type of phenomenon in the region. In addition, we analyse two recent catastrophic trans-national LLOFs occurring in the Sutlej river basin during 2000 and 2005. Based on high resolution satellite images, Tropical Rainfall Measuring Mission (TRMM), Moderate-Resolution Imaging Spectroradiometer (MODIS) derived evolution of snowline elevation and discharge data we reconstruct the timing and hydrometeorological conditions related to the formation and failure of landslide dams. Results showed that the 2005 flood, originating from the outburst of the Parchu Lake, was not related to heavy precipitation, but was likely enhanced by the rapid and late snowmelt of an unusually deep and widespread snowpack. The flood in 2000 was triggered by the outburst of an unnamed lake located on the Tibetan plateau, identified here for the first time. In this case, the outburst followed intense precipitation in the lake watershed, which raised the level of the lake and thus caused the breaching of the dam. As stream gauges were damaged during the events detailed discharge data is not available, but we estimated the peak discharges ranging between 1100 m3 s−1 and 2000 m3 s−1 in 2005, and 1024 m3 s−1 and 1800 m3 s−1 in 2000. These events caused significant geomorphic changes along the river valleys, with observed changes in channel width exceeding 200 m. Results also demonstrate that remotely-sensed data enables valuable large-scale monitoring of lake development and related hydrometeorological conditions, and may thereby inform early warning strategies, and provide a basis for flood risk reduction measures that focus on disaster preparedness and response strategies.

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