Geomorphological Analysis of Xilokastro Fault, Central Gulf of Corinth, Greece

The Gulf of Corinth is a rapidly opening area with high seismicity associated with extensive building collapses, destruction of cities, and even the deaths of inhabitants. Rapid residential development, especially in the southern part of the Gulf of Corinth, and the construction of crucial technical infrastructures necessitate understanding the activity across crustal-scale faults that host devastating earthquakes. The evolution of landforms affected by fault action is a dominant issue in geological science. In the present study, was selected the 20 km long Xilokastro pure normal fault. In this fault, we apply eight geomorphological indices in footwall catchments that drain perpendicular to its trace. In total, more than 5000 measurements were made in 102 catchments. The determination of geomorphological indices requires the construction of morphological profiles either perpendicular to the faults or perpendicular to the main tributaries of the drainage basins under consideration through the use of the geographical information systems (ArcGIS platform). Τhe application of these indices along catchments draining the Xilokastro fault scarp show high active tectonics. Its high activity is evidenced by the high values of the length-slope index near the fault trace, the low values of the width to height ratio index, the strong asymmetry of the drainage basins, especially in the overlapping zones between its segments, and the elongated shape of the drainage basins. This study supports the idea that the application of a single morphometric index is unable to reflect the distribution of active tectonics across faults, which makes inevitable the systematic comparison of a series of tectonic morphometric indices from which a new combined index emerges (Iat). The Iat classifies the Xilokastro fault in the high degree of activity at a rate of 75% of its length.

Snow Water Equivalent Change Mapping from Slope Correlated InSAR Phase Variations

Area-based measurements of snow water equivalent (SWE) are important for understanding earth system processes such as glacier mass balance, winter hydrological storage in drainage basins and ground thermal regimes. Remote sensing techniques are ideally suited for wide-scale area-based mapping with the most commonly used technique to measure SWE being passive-microwave, which is limited to coarse spatial resolutions of 25 km or greater, and to areas without significant topographic variation. Passive-microwave also has a negative bias for large SWE. Repeat-pass synthetic aperture radar interferometry (InSAR) as an alternate technique allows measurement of SWE change at much higher spatial resolution. However, it has not been widely adopted because: (1) the phase unwrapping problem has not been robustly addressed, especially for interferograms with poor coherence and; (2) SWE change maps scaled directly from repeat-pass interferograms are not an absolute measurement but contain unknown offsets for each contiguous coherent area. We develop and test a novel method for repeat-pass InSAR based dry-snow SWE estimation that exploits the sensitivity of the dry-snow refraction-induced InSAR phase to topographic variations. The method robustly estimates absolute SWE change at spatial resolutions of < 1 km, without the need for phase unwrapping. We derive a quantitative signal model for this new SWE change estimator and identify the relevant sources of bias. The method is demonstrated using both simulated SWE distributions and a 9-year RADARSAT-2 spotlight-mode dataset near Inuvik, NWT, Canada. SWE results are compared to in situ snow survey measurements and estimates from ERA5 reanalysis. Our method performs well in high-relief areas and in areas with high SWE (> 150 mm), thus providing complementary coverage to other passive- and active-microwave based SWE estimation methods. Further, our method has the advantage of requiring only a single wavelength band and thus can utilize existing spaceborne synthetic aperture radar systems. In application, a first order analysis of SWE trends within three drainage basins suggests that differences between basin-level accumulations are a function of major landcover types, and that re-vegetation following a forest-tundra fire that occurred over 50 years ago continues to affect the spatial distribution of SWE accumulation in the study area.

Quantifying the Geomorphology of the Drainage Basins Along the Greater Khingan Mountains in NE China

Drainage basins are fundamental elements of the earth’s surface, and quantifying their geomorphic features is essential to understand the interaction between tectonics, climatic, and surface processes. In this study, 40 basins of the Greater Khingan Mountains were selected for hypsometric analysis using a 90-m Shuttle Radar Topography Mission digital elevation model. The hypsometric integral values range from 0.13 to 0.44, with an average value of 0.30, and most hypsometric curves exhibit remarkable downward concave shapes. This feature indicates that most drainage basins and the landscape of the Greater Khingan Mountains are approaching the old-age development stage, consistent with the present moderately stable tectonic activity. The spatial distribution of the χ values is characterized by unambiguously higher values on the western flank than those on the eastern flank in the middle and southern segments of the Greater Khingan Mountains. We interpret this as an indicator of the disequilibrium across the main divide. The interpolation of the erosion rates and channel steepness for the catchments on both sides of the Greater Khingan Mountains revealed westward divide migration, which is consistent with the lower χ values, a higher slope, and local relief observed along the eastern flanks. Considering the long-term tectonic evolution pattern between the Greater Khingan Mountains and Songliao Basin, the landscape decay and slow westward divide migration were mostly driven by the inherited Cenozoic tectonics and precipitation gradient across East Asia.

Case Study of Urban Flood Inundation—Impact of Temporal Variability in Rainfall Events

This study aimed to calculate and analyze total overflows that accumulate in urban manholes in the target drainage basin of Samsung-dong, Seoul in heavy rainfall events with different temporal distribution characteristics, using the EPA’s Storm Water Management Model (EPA-SWMM model). Inundation behaviors were analyzed using the two-dimensional flood model (FLO-2D). The extreme rainfall events were produced using different exceedance probability Huff distributions for different durations and return periods, such as from 1 to 3 h and 10 years, 50 years, 80 years, 100 years, respectively. The inundation model was validated using the actual flood observations on 21 September 2010 in the Samsung-dong drainage basin. The total overflow amount showed considerable differences according to the different time distribution characteristics, such as the temporal location of the storm peak and the concentration level of the storm. Furthermore, the inundation behaviors were also related to the temporal characteristics of storms. The results illustrated that the consideration of the temporal distribution characteristics of extreme rainfall events is essential for an accurate understanding of the rainfall–runoff response and inundation behavior in urban drainage basins.

High-resolution modeling of glacier mass balance and surface runoff in western Norway driven by bias-corrected climate forcing

Western Norway hosts many glacierized drainage basins with complex terrain and local climate. These drainage basins face challenges related to long-term planning of hydropower production and flood risk mitigation under global warming. To enable forward vision of such efforts, bias-corrected outputs from state-of-the-art regional climate models and reanalysis provide climatic forcing for impact simulations. We utilize a distributed, process-based snow evolution model with a daily temporal and 100 m × 100 m spatial resolution to investigate the applicability of different bias-corrected climate forcing data for multidecadal reconstructions of glacier surface mass balance and surface runoff regimes in western Norway. These simulations are driven by climatic forcing from the bias-corrected NORA10 hindcast in 2000–2014, which has been produced specifically for western Norway and treated as a benchmark dataset, as well as ten bias-corrected and uncorrected CORDEX outputs under different Representative Concentration Pathway scenarios in 2000–2020. Downscaled drainage basin-wide air temperature, precipitation and glacier-wide surface mass balance are then validated against observations. The variables mentioned above produced by the benchmark simulation match available observations well. The mean annual surface mass balance of glaciers in most glacierized basins is negative in 2001–2014, and its evolution is mainly correlated with trends in annual snowfall. There is a general negative west to east gradient in seasonal and annual unit area runoff, which peaks between 2005 and 2008 in most drainage basins. Snow meltwater is the largest contributor to both seasonal and annual runoff in all drainage basins except for two of the westernmost ones. Drainage basins with denser glacier coverage turn out to have a later peak runoff discharge date. The correction applied to the CORDEX forcing reversed the cold bias in the original datasets, while the agreement between bias-corrected and observed precipitation rates varies strongly from basin to basin. As a result, simulations driven by bias-corrected CORDEX datasets produce lower annual surface mass balance in the most and least glacierized drainage basins, i.e., Basin 1 and 17, respectively. They all produce more unit area runoff in Basin 1 and less in Basin 17 both seasonally and annually, with only a few exceptions. We conclude that the identified errors will likely be inherited by the results of the future projections, casting doubts on the applicability of bias-corrected CORDEX forcing to directly drive local scale projections and the modeled outputs in developing climate change adaptation strategies.

Evaluation of Satellite-Derived Products for the Daily Average and Extreme Rainfall in the Mearim River Drainage Basin (Maranhão, Brazil)

Satellite precipitation estimates are used as an alternative or as a supplement to the records of the in situ stations. Although some satellite precipitation products have reasonably consistent time series, they are often limited to specific geographic areas. The main objective of this study was to evaluate CHIRPS version 2, MSWEP version 2, and PERSIANN-CDR, compared to gridBR, as daily mean and extreme inputs represented on a monthly scale and their respective seasonal trends of rainfall in the Mearim River Drainage Basin (MDB), Maranhão state, Brazil. Estimates of errors were calculated (relative error, pbias; root mean square error, RMSE, and Willmott concordance index, d), and the chances of precipitation were estimated by remote sensing (RES). In addition, trends in precipitation were estimated by the two-sample Mann–Kendall test. Given the overall performance, the best products for estimating monthly mean daily rainfall in the MDB are CHIRPS and PERSIANN-CDR, especially for rainy months (December to May). For daily extremes on the monthly scale, the best RES is PERSIANN-CDR. There is no general agreement between gridBR and RES methods for the trend signal, even a nonsignificant one, much less a significant one. The use of MSWEP for the MDB region is discouraged by this study because it overestimates monthly averages and extremes. Finally, studies of this kind in drainage basins are essential to improve the information generated for managing territories and developing regionalized climate and hydrological models.

Study on the driven mechanism of hydrologic drought based on the lithology-combined structure of the Karst drainage basin in South China

Hydrologic drought, considered as a typical natural phenomenon in the background of global climate changes, is the continuation and development of meteorological and agricultural droughts, and is the ultimate and most thoroughly drought. The research area controlled by the 55 hydrological sections in South China is selected in this paper, and the intensity and frequency of hydrologic droughts are analyzed by the Standardized Runoff Index (SRI), and the driven mechanism of watershed lithologies to hydrologic droughts is discussed. The results show that (i) the hydrological drought of Karst drainage basins is shown the gradual aggravation from the west to east parts in South China, with the significant north–south stripe distributions at the SRI_3 and SRI_6; (ii) the occurring probability of hydrological droughts is the Limestone-type Karst Basin (II and III, 0.17) &lt; Dolomite-type Karst Basin (I and IV, 0.22) &lt; Non-Karst Basin (V, 0.25) in terms of combination types of basin lithologies, and (iii) the Karst Basin (I and III, 0.18) &lt; Semi-Karst Basin (II and IV, 0.2) &lt; Non-Karst Basin (V, 0.25) in terms of basin lithologies. Therefore, this proves that the most water-stored spaces are found in Karst Basins under the differential dissolution or erosion effects of soluble water, followed by in the Semi-Karst Basin, the least water-stored spaces in the Non-Karst Basin.

GIS-based Assessment of Morphological and Hydrological Parameters of Ribeira dos Socorridos and Ribeira do Vigario Basins, Madeira Island, Portugal

The main objective is to identify hydraulic and hydrologic features of drainage basins of Ribeira dos Socorridos, and Ribeira do Vigário located in Madeira Island, (Câmara de Lobos).So, the research analyzed, theoretically, the sediment transport in the above-mentioned cases, and consequently, possible measures for torrential correction were studied. Thereby, hydrographic, geological, and hydrological features of this Archipelago were analyzed in the first phase. Thus, a geographic framing of drainage basins was made - using digital terrain models and deep characterization of the understudy drainage basins. In this regard, it was possible to obtain data regarding the geometric, relief, and drainage system components, using the Geographic Information Systems (GIS).In fact, the use of GIS makes it possible to characterize all descriptive indices/parameters of a hydrographic basin. These indices/parameters linked to the region's climate explain the need for human intervention to construct river hydraulic infrastructure and implement mitigation measures.Moreover, torrential correction techniques were presented to anticipate and mitigate this typology of events. Contextually, this study provides us several goals to consider in the future, including the most relevant actions and guidelines to enhance the characterization of drainage basins and clarify the characterization and accounting of sediment transport.