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GeoHazards, Volume 1, Issue 1 (September 2020) – 3 articles

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Open AccessFeature PaperArticle
A Remote Sensing-Based Method to Assess Water Level Fluctuations in Wetlands in Southern Brazil
GeoHazards 2020, 1(1), 20-30; https://doi.org/10.3390/geohazards1010003 - 12 May 2020
Viewed by 218
Abstract
The characterization of water level fluctuations is crucial to explain the hydrological processes that contribute to the maintenance of the structure and function of wetlands. The aim of this study was to develop a method based on remote sensing to characterize and map [...] Read more.
The characterization of water level fluctuations is crucial to explain the hydrological processes that contribute to the maintenance of the structure and function of wetlands. The aim of this study was to develop a method based on remote sensing to characterize and map the water level variation patterns, evapotranspiration, discharge, and rainfall over wetlands in the Gravataí River basin, Rio Grande do Sul (RS), Brazil. For this purpose, ground-based measurements of rainfall, water discharge, and evapotranspiration together with satellite data were used to identify the apparent water level based on the normalized difference water index (NDWI). Our results showed that the variation of the water level followed the rainfall, water discharge, and evapotranspiration seasonal patterns in the region. The NDWI showed similar values to the ground-based data collected 10 days prior to satellite image acquisition. The proposed technique allows for quantifying the pattern of flood pulses, which play an important role for establishing the connectivity between different compartments of wetlands in the study area. We conclude that our methodology based on the use of satellite data and ground measurements was a useful proposition to analyze the water level variation patterns in an area of great importance in terms of environmental degradation and use of agriculture. The information obtained may be used as inputs in hydrologic models, allowing researchers to evaluate the impact, at both local and regional scales, caused by advance of agriculture into natural environments such as wetlands. Full article
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Open AccessArticle
Soil–Water Retention Curves Derived as a Function of Soil Dry Density
GeoHazards 2020, 1(1), 3-19; https://doi.org/10.3390/geohazards1010002 - 27 Aug 2018
Cited by 3 | Viewed by 990
Abstract
The soil–water retention curves (SWRC) of soil plays a key role in unsaturated soil mechanics, which is a relatively new field of study having wide applications particularly in geotechnical and geo-environmental engineering. SWRCs were used to evaluate the ability of unsaturated soils to [...] Read more.
The soil–water retention curves (SWRC) of soil plays a key role in unsaturated soil mechanics, which is a relatively new field of study having wide applications particularly in geotechnical and geo-environmental engineering. SWRCs were used to evaluate the ability of unsaturated soils to attract water with various water contents and matric suctions. Drying and wetting SWRCs for a sandy soil with different dry densities were studied in a laboratory. Proton nuclear magnetic resonance, image processing technology, and mercury intrusion porosimetry were used to characterize the microscopic mechanisms of pore size distribution in the soil. Soil–water retention in the soil samples was strongly dependent on the dry density. With zero matric suction, soil samples with a higher dry density had a lower initial volumetric water content. Volumetric water content changed at a slower rate when values of matric suction increased in soils with a higher dry density. Soil samples had residual matric suction and a larger air-entry value with a smaller slope of the SWRC when they had a higher density. Dry density change is mainly responsible for the large pores. The number of large pores decreased as dry density increased. As the dry density increased, the area of macropores occupying the largest portion decreased, while the area of mesopores and micropores increased. Minipores accounted for the smallest proportion of total area and they were nearly constant. The proportion of large diameter pores decreased relative to pores with small diameters in the tested soils. The total pore volume was lower for soil specimens that had larger dry densities, as compared to relatively loose specimens. There was hysteresis between the drying and wetting curves for all soil samples. Hysteresis decreased as the dry density of the soil increased. The different liquid–solid contact angle was the main factor causing hysteresis of SWRC. Full article
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Open AccessEditorial
GeoHazards: A New Interdisciplinary Journal Devoted to the Study of Geomorphological Hazards
GeoHazards 2020, 1(1), 1-2; https://doi.org/10.3390/geohazards1010001 - 02 Jun 2018
Viewed by 960
Abstract
The name GeoHazards comes from the word “geomorphological”, which refers to the study of the physical features of the surface of the earth and their relation to its geological structures, and the word “hazard”, meaning an agent which has the potential to cause [...] Read more.
The name GeoHazards comes from the word “geomorphological”, which refers to the study of the physical features of the surface of the earth and their relation to its geological structures, and the word “hazard”, meaning an agent which has the potential to cause harm to a vulnerable target[...] Full article
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