The rapid glacial-proglacial landscape modification at Pasterze Glacier in a one-year period as revealed by multiple aerial flight and field campaigns

2020 ◽  
Author(s):  
Gernot Seier ◽  
Andreas Kellerer-Pirklbauer ◽  
Wolfgang Sulzer ◽  
Christian Ziesler ◽  
Philipp Krisch ◽  
...  
Keyword(s):  
Water Level ◽  
Transition Zone ◽  
Diurnal Cycle ◽  
Horizontal Displacement ◽  
Aerial Imagery ◽  
Visual Interpretation ◽  
Landscape Modification ◽  
Glacier Tongue ◽  
Ground Truthing ◽  
Mean Square Errors

<p>The Pasterze Glacier is an approx. 16 km² large and rapidly receding glacier in the Austrian Alps. The aim of this study was to detect and quantify the rapid landscape modification of its glacial-proglacial transition zone between September 2018 and September 2019. The study is primarily based on the analysis of aerial imagery of five different acquisition dates, two in 2018 (11 September and 15 November) and three in 2019 (17 June, 13 and 21 September). The platforms used for data acquisition comprised unmanned and manned aircrafts that led to ground sampling distances (GSDs) of the aerial imagery of approx. 10 cm. These data were photogrammetrically processed to orthophotos and digital elevation models (DEMs), which are the main input for the subsequent analysis. The flight campaigns were complemented mainly with geodetic measurements for ground-truthing purposes, water level measurements and field observations in order to facilitate a better geomorphological and glaciological interpretation.</p><p>Thickness changes and horizontal displacement of the Pasterze Glacier tongue and its adjacent proglacial transition zone were detected applying DEM differencing and normalized cross-calculation (orthophotos). These analyses also included a quality assessment, which allowed to discriminate changes from unchanged subareas. By visual interpretation of the orthophotos and our in-situ measurements, we detected substantial geomorphic changes, the further evolution of the proglacial lake’s extent and water level changes.</p><p>Results show that the thickness of the investigated subarea at the glacier tongue (0.2 km²) decreased up to approx. 18 m from June 2019 to September 2019 with a mean ice thickness decrease of approx. 4.2 m. In contrast, a subarea of the studied proglacial area (0.14 km²) remained rather unchanged (mean thickness decrease of only 0.7 m). Taking into account the comparison of DEM elevation values with geodetically and thus independent elevation measurements, the vertical quality of the DEMs is described by a standard deviation of 0.14-0.16 m and a mean of 0.07 m. The Root Mean Square Errors of the GCPs are 0.08-0.13 m in planimetry and 0.10-0.16 m in heights.</p><p>Comparing the orthophotos of June 2019 and September 2019 shows a distinct expansion of the glacier lake towards the eastern part of the debris-covered glacier tongue by several meters in one summer only. The lake level shows a clear diurnal cycle of typically around 20 cm during sunny days (high irradiation) and changes in the order of half a meter over the entire summer season. Water temperatures of the lake follow a clear diurnal cycle, too with typical values between 1°C and 3°C.</p><p>We conclude that the Pasterze Glacier tongue and its adjacent proglacial area changed rapidly in terms of glacier surfaces modification and in terms of proglacial changes on an annual (September 2018 to September 2019) and sub-annual (June to September 2019) time-scale.</p>

Water-level regulation and coastal wetland vegetation in the upper St. Lawrence River: inferences from historical aerial imagery, seed banks, and Typha dynamics

Hydrobiologia ◽  
2009 ◽  
Vol 647 (1) ◽  
pp. 127-144 ◽  
Author(s):  
John M. Farrell ◽  
Brent A. Murry ◽  
Donald J. Leopold ◽  
Alison Halpern ◽  
Molly Beland Rippke ◽  
...  
Keyword(s):  
Water Level ◽  
Coastal Wetland ◽  
Seed Banks ◽  
Wetland Vegetation ◽  
Aerial Imagery ◽  
St Lawrence River ◽  
Water Level Regulation

Stability Evaluation for Cut-Off Wall of Daning Reservoir during Operation Period

2012 ◽  
Vol 212-213 ◽  
pp. 835-840
Author(s):  
Miao Liu ◽  
Zhi Yin Wang ◽  
Qi Wei Zhang ◽  
Jing Chun Li
Keyword(s):  
Water Level ◽  
Horizontal Displacement ◽  
Good Effect ◽  
Concrete Wall ◽  
The Maximum Principle ◽  
Vehicle Load ◽  
Fluid Load ◽  
Guide Wall ◽  
Reinforced Concrete Wall ◽  
Stress And Deformation

The stress and deformation of cut-off wall will be changed as the water level cyclical varying during reservoir's operation. Therefore, the prediction is important to the safety and stability of reservoir. In this paper, the seepage characteristics of the highest and the lowest water level condition have been predicted, and the variation of horizontal displacement is discussed under the vehicle load of road and cyclical fluid load. Meanwhile, the displacement distribution and stress state in junction area of the upper wall and the lower wall are obtained. The results show that the Cut-off wall is less affected by the vehicle load of road, and its stress and deformation will gradually stabilize after the second water store-discharge cycle. The upper reinforced concrete wall will tilt towards outside of reservoir, but the deformation is very small at lower plastic concrete wall. The guide wall has a good effect on preventing the upper wall's inclining and improving the lower wall's stress environment. Besides, the maximum principle stress of cut-off wall is too small to course plastic failure.

Analysis of Wetland Ecosystem Response of Poyang Lake with Water Level Evolution Base on TM Images

2013 ◽  
Vol 295-298 ◽  
pp. 1935-1940 ◽  
Author(s):  
Yu Ru Lin ◽  
Ya Ping Du ◽  
Hua Mei Yang
Keyword(s):  
Spatial Distribution ◽  
Water Level ◽  
Transition Zone ◽  
Poyang Lake ◽  
Ecological System ◽  
Hydrological Process ◽  
Wetland Ecosystem ◽  
Ecosystem Response ◽  
Hydrologic Data ◽  
Optimum Water

The response of wetland ecosystem of Poyang Lake influenced by hydrological process changes was addressed. The spatial distribution and area of water, water-land transition zone and exposed grass continent were obtained by classification and extraction of wetland based on Landsat-TM images and analysis of observed hydrologic data. The results indicated that wetland ecological system of Poyang Lake was characteristic of complexity,sensitivity,mutability and fragility, and the optimum water level of wetland in Poyang Lake was 10-14m.

scholarly journals Factors affecting the distribution of fish during receding flood in lower Irtysh: effects of water level and diurnal cycle

2015 ◽  
Vol 51 (2) ◽  
pp. 89-100
Author(s):  
A. D. Mochek ◽  
E. S. Borisenko ◽  
D. S. Pavlov ◽  
A. A. Chemagin ◽  
S. V. Budaev
Keyword(s):  
Water Level ◽  
Diurnal Cycle ◽  
Factors Affecting ◽  
Distribution Of Fish

scholarly journals The use of B-splines to represent the topography of river networks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Eva Boergens ◽  
Michael Schmidt ◽  
Florian Seitz
Keyword(s):  
Standard Deviation ◽  
Water Level ◽  
River Networks ◽  
Distributed Data ◽  
Outlier Removal ◽  
Directed Tree ◽  
B Splines ◽  
Tree Graphs ◽  
Main Challenge ◽  
Mean Square Errors

AbstractThis work presents a new extension to B-Splines that enables them to model functions on directed tree graphs such as non-braided river networks. The main challenge of the application of B-splines to graphs is their definition in the neighbourhood of nodes with more than two incident edges. Achieving that the B-splines are continuous at these points is non-trivial. For both, simplification reasons and in view of our application, we limit the graphs to directed tree graphs. To fulfil the requirement of continuity, the knots defining the B-Splines need to be located symmetrically along the edges with the same direction. With such defined B-Splines, we approximate the topography of the Mekong River system from scattered height data along the river. To this end, we first test and validate successfully the method with synthetic water level data, with and without added annual signal. The quality of the resulting heights is assessed besides others by means of root mean square errors (RMSE) and mean absolute differences (MAD). The RMSE values are 0.26 m and 1.05 m without and with added annual variation respectively and the MAD values are even lower with 0.11 m and 0.60 m. For the second test, we use real water level observations measured by satellite altimetry. Again, we successfully estimate the river topography, but also discuss the short comings and problems with unevenly distributed data. The unevenly distributed data leads to some very large outliers close to the upstream ends of the rivers tributaries and in regions with rapidly changing topography such as the Mekong Falls. Without the outlier removal the standard deviation of the resulting heights can be as large as 50 m with a mean value of 15.73 m. After the outlier removal the mean standard deviation drops to 8.34 m.

scholarly journals Seepage, Deformation, and Stability Analysis of Sandy and Clay Slopes with Different Permeability Anisotropy Characteristics Affected by Reservoir Water Level Fluctuations

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 201 ◽  
Author(s):  
Shuyang Yu ◽  
Xuhua Ren ◽  
Jixun Zhang ◽  
Haijun Wang ◽  
Junlei Wang ◽  
...  
Keyword(s):  
Water Level ◽  
Horizontal Displacement ◽  
Water Level Fluctuations ◽  
Anisotropy Ratio ◽  
Soil Slope ◽  
Infiltration Capacity ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Pressure Stress ◽  
Anisotropy Direction

Evaluation of slope stability under water level fluctuations is an important topic in the Three Gorges Reservoir (TGR) in China. However, most of the previous studies regarded slope soil as isotropic material, or only considered the influence of anisotropy ratio (kr = kx/ky) but ignored the anisotropy direction (α). Meanwhile, the pore pressure–stress coupling was rarely considered in the previous numerical simulations. In the present study, the SIGMA/W and SLOPE/W modules in Geo-studio are utilized to carry out the numerical simulation of Caipo slope under the drawdown of the reservoir water level, and the anisotropy ratio (kr) as well as the anisotropy direction (α) of two kinds of soils (clay and sand) are included. Results show that the anisotropy ratio kr and anisotropy direction α decrease the infiltration capacity of the soil, which increases the infiltration line hysteretic elevation (ILHE) as well as maximum horizontal displacement (MHD), and reduces the minimum safety factor (MSF). The slope toe firstly fails with the drawdown of water level. The influence of reservoir water level drop on seepage, deformation, and stability of the sand slope is less than that of the clay slope. For the sandy soil slope, it is not only necessary to consider the influence of kr, but also the influence of α. For the soil slope, we can only consider α in order to simplify calculation.

scholarly journals Extracting Impervious Surface from Aerial Imagery Using Semi-Automatic Sampling and Spectral Stability

2020 ◽  
Vol 12 (3) ◽  
pp. 506
Author(s):  
Hua Zhang ◽  
Steven M. Gorelick ◽  
Paul V. Zimba
Keyword(s):  
Remote Sensing ◽  
Land Cover ◽  
Land Development ◽  
Impervious Surface ◽  
Data Availability ◽  
Aerial Imagery ◽  
Visual Interpretation ◽  
Medium Resolution ◽  
Two Factors ◽  
Wetland Inventory

The quantification of impervious surface through remote sensing provides critical information for urban planning and environmental management. The acquisition of quality reference data and the selection of effective predictor variables are two factors that contribute to the low accuracies of impervious surface in urban remote sensing. A hybrid method was developed to improve the extraction of impervious surface from high-resolution aerial imagery. This method integrates ancillary datasets from OpenStreetMap, National Wetland Inventory, and National Cropland Data to generate training and validation samples in a semi-automatic manner, significantly reducing the effort of visual interpretation and manual labeling. Satellite-derived surface reflectance stability is incorporated to improve the separation of impervious surface from other land cover classes. This method was applied to 1-m National Agriculture Imagery Program (NAIP) imagery of three sites with different levels of land development and data availability. Results indicate improved extractions of impervious surface with user’s accuracies ranging from 69% to 90% and producer’s accuracies from 88% to 95%. The results were compared to the 30-m percent impervious surface data of the National Land Cover Database, demonstrating the potential of this method to validate and complement satellite-derived medium-resolution datasets of urban land cover and land use.

scholarly journals Observed and Modeled Growing-Season Diurnal Precipitable Water Vapor in South-Central Canada

2010 ◽  
Vol 49 (11) ◽  
pp. 2301-2314 ◽  
Author(s):  
John Hanesiak ◽  
Mark Melsness ◽  
Richard Raddatz
Keyword(s):  
Water Vapor ◽  
Diurnal Cycle ◽  
Deep Convection ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
High Temporal Resolution ◽  
Forecast Period ◽  
Growing Seasons ◽  
South Central ◽  
Mean Square Errors

Abstract High-temporal-resolution total-column precipitable water vapor (PWV) was measured using a Radiometrics Corporation WVR-1100 Atmospheric Microwave Radiometer (AMR). The AMR was deployed at the University of Manitoba in Winnipeg, Canada, during the 2003 and 2006 growing seasons (mid-May–end of August). PWV data were examined 1) to document the diurnal cycle of PWV and to provide insight into the various processes controlling this cycle and 2) to assess the accuracy of the Canadian regional Global Environmental Multiscale (GEM) model analysis and forecasts (out to 36 h) of PWV. The mean daily PWV was 22.6 mm in 2003 and 23.8 mm in 2006, with distinct diurnal amplitudes of 1.5 and 1.8 mm, respectively. It was determined that the diurnal cycle of PWV about the daily mean value was controlled by evapotranspiration (ET) and the occurrence/timing of deep convection. The PWV in both years reached its hourly maximum later in the afternoon as opposed to at solar noon. This suggested that the surface and atmosphere were well coupled, with ET primarily being controlled by the vapor pressure deficit between the vegetation/surface and atmosphere. The decrease in PWV during the evening and overnight periods of both years was likely the result of deep convection, with or without precipitation, which drew water vapor out of the atmosphere, as well as the nocturnal decline in ET. The results did not change for days on which low-level winds were light (i.e., maximum winds from the surface to 850 hPa were below 20 km h−1), which supports the notion that the diurnal PWV pattern was associated with the daily cycles of local ET and convection/precipitation and was not due to advection. Comparison of AMR PWV with the Canadian GEM model for the growing seasons of 2003 and 2006 indicated that the model error was 3 mm (13%) or more even in the first 12 h, with mean absolute errors ranging from 2 to 3.5 mm and root-mean-square errors from 3 to 4.5 mm over the full 36-h forecast period. It was also found that the 3–9-h forecast period of GEM had better error scores in 2006 than in 2003.

scholarly journals On-site sanitation density and groundwater quality: evidence from remote sensing and in situ observations in the Thiaroye aquifer, Senegal

2020 ◽  
Vol 10 (4) ◽  
pp. 927-939
Author(s):  
Mor Talla Diaw ◽  
Seynabou Cissé-Faye ◽  
Cheikh Becaye Gaye ◽  
Seydou Niang ◽  
Abdoulaye Pouye ◽  
...  
Keyword(s):  
Groundwater Quality ◽  
Low Income ◽  
Urban Areas ◽  
Low Cost ◽  
Scientific Evidence ◽  
Shallow Groundwater ◽  
Visual Interpretation ◽  
Guideline Value ◽  
Ground Truthing ◽  
Optical Satellite Images

Abstract In rapidly urbanising low-income towns and cities, there remains an absence of scientific evidence and regulatory structures to sustain the quality and quantity of groundwater used for low-cost water supplies and to reconcile this with continued use of the subsurface for low-cost sanitation. Here, we analyse the relationship between the density of on-site sanitation and shallow groundwater quality in the Thiaroye aquifer of Quaternary sands in Dakar, Senegal. On-site sanitation was mapped using object-oriented classification and visual interpretation of high-resolution, optical satellite images and ground-truthing surveys. Groundwater quality was assessed over a three-year period (2017–2019) from a network of 61 sources comprising boreholes, dug-wells, hand tubewells and piezometers. More than 253,000 on-site sanitation facilities are identified over an area of 520 km2 with densities ranging from 1 to 70 per hectare. A moderate, statistically significant linear relationship (r2 = 0.55, p « 0.01) is found between the density of on-site sanitation facilities and nitrate concentrations in sampled groundwater sources. Groundwater contamination beyond the WHO drinking-water guideline value (50 mg/L) occurs where densities of on-site sanitation facilities exceed 4 (±4) per hectare, a threshold commonly surpassed in peri-urban areas underlain by the Thiaroye aquifer of Dakar.

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