scholarly journals Hydrogeomorphic Impacts of Floods in a First-Order Catchment: Integrated Approach Based on Dendrogeomorphic Palaeostage Indicators, 2D Hydraulic Modelling and Sedimentological Parameters

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 212 ◽  
Author(s):  
Radek Tichavský ◽  
Stanislav Ruman ◽  
Tomáš Galia
Keyword(s):  
Peak Flow ◽  
Flash Flood ◽  
Integrated Approach ◽  
Hydraulic Modelling ◽  
Channel Stability ◽  
Stream Channels ◽  
Stream Power ◽  
First Order ◽  
Fine Sediments ◽  
Critical Unit

Floods represent frequent hazards in both low- and first-order catchments; however, to date, the investigation of peak flow discharges in the latter catchments has been omitted due to the absence of gauging stations. The quantification of flood parameters in a first-order catchment (1.8 km2) was realised in the moderate relief of NE Czechia, where the last flash flood event in 2014 caused considerable damage to the infrastructure. We used an integrated approach that included the dendrogeomorphic reconstruction of past flood activity, hydraulic modelling of the 2014 flash flood parameters using a two-dimensional IBER model, and evaluation of the channel stability using sedimentological parameters. Based on 115 flood scars, we identified 13 flood events during the period of 1955 to 2018, with the strongest signals recorded in 2014, 2009 and 1977. The modelled peak flow discharge of the last 2014 flood was equal to 4.5 m3·s−1 (RMSE = 0.32 m) using 26 scars as palaeostage indicators. The excess critical unit stream power was observed at only 24.2% of the reaches, representing predominantly bedrock and fine sediments. Despite local damage during the last flood, our results suggest relatively stable geomorphic conditions and gradual development of stream channels under discharges similar to that in 2014.

An integrated approach of ground and aerial observations in flash flood disaster investigations. The case of the 2017 Mandra flash flood in Greece

2019 ◽  
Vol 33 ◽  
pp. 290-309 ◽  
Author(s):  
M. Diakakis ◽  
E. Andreadakis ◽  
E.I. Nikolopoulos ◽  
N.I. Spyrou ◽  
M.E. Gogou ◽  
...  
Keyword(s):  
Flash Flood ◽  
Integrated Approach ◽  
Flood Disaster

scholarly journals Impacts of Triple Factors on Flash Flood Vulnerability in Egypt: Urban Growth, Extreme Climate, and Mismanagement

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 24 ◽  
Author(s):  
Mohamed Saber ◽  
Karim I. Abdrabo ◽  
Omar M. Habiba ◽  
Sameh A. Kantosh ◽  
Tetsuya Sumi
Keyword(s):  
Urban Growth ◽  
Flash Flood ◽  
Integrated Approach ◽  
Annual Rainfall ◽  
Flood Hazards ◽  
Hazard Maps ◽  
Flood Vulnerability ◽  
Rainfall Analysis ◽  
Climatic Regions ◽  
Extreme Climate

Urban growth, extreme climate, and mismanagement are crucial controlling factors that affect flood vulnerability at wadi catchments. Therefore, this study attempts to understand the impacts of these three factors on the flash flood vulnerability in different climatic regions in Egypt. An integrated approach is presented to evaluate the urban growth from 1984 to 2019 by using Google Images and SENTINEL-2 data, and to develop hazard maps by using a rainfall-runoff-inundation model (RRI). Annual rainfall trend analysis was performed to evaluate the temporal variability trend. The hazard maps that were created were classified into three categories (low, medium, and high) and integrated with the urban growth maps to evaluate the impacts on the flood-vulnerable areas. The results show a significant increase in urban growth resulting in an increase of prone areas for flood hazards over time. However, the degree of this hazard is mainly related to growth directions. Mismanagement affects urban growth directions in both planned and unplanned growth, whether by loss of control over unplanned growth or by deficiencies in approved plans. The rainfall analysis showed that there is no explicit relationship to increases or decreases in the flood vulnerable areas. An urban planning approach is recommended for risk reduction management based on a comprehensive study considering such factors.

scholarly journals Estimation of flash flood hazard in the Pidima-Arfara area (Messinia, SW Greece), based on the study of instantaneous unitary hydrographs, longitudinal profilesand stream power

2007 ◽  
Vol 40 (4) ◽  
pp. 1621
Author(s):  
E. Sambaziotis ◽  
I. Fountoulis
Keyword(s):  
Flash Flood ◽  
Flood Hazard ◽  
Flash Floods ◽  
Topographic Map ◽  
Stream Power ◽  
Longitudinal Gradient ◽  
Hydrological Simulation ◽  
Small Catchment ◽  
Map Scale ◽  
Good Agreement

In this paper it is an effort to combine different methodologies in order to locate the sensitive sites in flash flood phenomena in a relatively small catchment located north of Kalamata (Messinia SW Péloponnèse, Greece). Based on digitised topographic map (scale 1/5.000) the longitudinal, gradient and stream power profiles of the watercourses were constructed and the results (possibly sensitive to flash floods sites) were compared to ones that came from applying hydrological simulation, hydrographs as well as Instantaneous Unitary Hydrographs. The comparison showed that the results were in good agreement.

scholarly journals Towards an increase of flash flood geomorphic effects due to gravel mining and ground subsidence in Nogalte stream (Murcia, SE Spain)

2016 ◽  
Vol 16 (10) ◽  
pp. 2273-2286 ◽  
Author(s):  
Jose Antonio Ortega-Becerril ◽  
Guillermina Garzón ◽  
Marta Béjar-Pizarro ◽  
Jose Jesús Martínez-Díaz
Keyword(s):  
Flash Flood ◽  
Time Lag ◽  
Alluvial Fan ◽  
Ground Subsidence ◽  
Flood Event ◽  
Stream Power ◽  
Base Level ◽  
Gravel Mining ◽  
Collateral Effects ◽  
Aquifer Overexploitation

Abstract. Transition from endorheic alluvial fan environments to well-channelized fluvial systems in natural conditions may occur in response to base-level fluctuations. However, human-induced changes in semi-arid regions can also be responsible for similar unforeseen modifications. Our results confirm that in-channel gravel mining and aquifer overexploitation over the last 50 years in the case study area have changed the natural stability of the Nogalte stream and, as a result, its geomorphic parameters including channel depth and longitudinal profile have begun to adapt to the new situation. Using interferometric synthetic aperture radar (InSAR) data we obtain maximum values for ground subsidence in the Upper Guadalentín Basin of  ∼ 10 cm yr−1 for the period 2003–2010. In this context of a lowered base level, the river is changing its natural flood model to a more powerful one. A comparison of the 1973 flood event, the most dramatic flood event ever recorded in the area, with the 2012 event, where there was a similar discharge but a sediment load deficit, reveals greater changes and a new flooding pattern and extension. In-channel gravel mining may be responsible for significant local changes in channel incision and profile. This, together with the collateral effects of aquifer overexploitation, can favour increased river velocity and stream power, which intensify the consequences of the flooding. The results obtained here clearly demonstrate an existing transition from the former alluvial pattern to a confined fluvial trend, which may become more pronounced in the future due to the time lag between the drop in aquifer level and ground subsidence, and introduce a new scenario to be taken into consideration in future natural hazard planning in this area.

scholarly journals Changes in Stream Peak Flow and Regulation in Naoli River Watershed as a Result of Wetland Loss

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Yunlong Yao ◽  
Lei Wang ◽  
Xianguo Lv ◽  
Hongxian Yu ◽  
Guofu Li
Keyword(s):  
Peak Flow ◽  
Daily Rainfall ◽  
Wetland Loss ◽  
Wetland Area ◽  
First Order ◽  
Rate Of Increase ◽  
Increasing Trend ◽  
Exponential Decay Model ◽  
Streamflow Data ◽  
Peak Streamflow

Hydrology helps determine the character of wetlands; wetlands, in turn, regulate water flow, which influences regional hydrology. To understand these dynamics, we studied the Naoli basin where, from 1954 to 2005, intensive marshland cultivation took place, and the watershed’s wetland area declined from94.4×104 ha to17.8×104 ha. More than 80% of the wetland area loss was due to conversion to farmland, especially from 1976 to 1986. The processes of transforming wetlands to cultivated land in the whole Naoli basin and subbasins can be described using a first order exponential decay model. To quantify the effects of wetlands cultivation, we analyzed daily rainfall and streamflow data measured from 1955 to 2005 at two stations (Baoqing Station and Caizuizi Station). We defined a streamflow regulation index (SRI) and applied a Mann-Kendall-Sneyers test to further analyze the data. As the wetland area decreased, the peak streamflow at the Caizuizi station increased, and less precipitation generated heavier peak flows, as the runoff was faster than before. The SRI from 1959 to 2005 showed an increasing trend; the SRI rate of increase was 0.05/10a, demonstrating that the watershed’s regulation of streamflow regulation was declined as the wetlands disappeared.

scholarly journals Towards an increase of flash-flood geomorphic effects due to gravel mining and ground subsidence in Nogalte stream (SE Spain, Murcia)

2016 ◽  
Author(s):  
Jose A. Ortega-Becerril ◽  
Guillermina Garzón ◽  
Marta Béjar-Pizarro ◽  
Jose Jesús Martínez-Díaz
Keyword(s):  
Flash Flood ◽  
Time Lag ◽  
Alluvial Fan ◽  
Ground Subsidence ◽  
Stream Power ◽  
Fluvial Systems ◽  
Base Level ◽  
Gravel Mining ◽  
Collateral Effects ◽  
Aquifer Overexploitation

Abstract. Transition from endorheic alluvial fan environments to well-channelized fluvial systems in natural conditions may occur in response to base-level fluctuations. However, human-induced changes in semi-arid regions can also be responsible for similar unforeseen modifications. Our results confirm that in-channel gravel mining and aquifer overexploitation over the last 50 years in the case study area have changed the natural stability of the Nogalte stream and, as a result, its geomorphic parameters including channel depth and longitudinal profile have begun to adapt to the new situation. Using interferometric synthetic aperture radar (InSAR) data we obtain maximum values for ground subsidence in the Upper Guadalentín basin of ~ 10 cm yr−1 for the period 2003–2010. In this context of a lowered base level, the river is changing its natural flood model to a more energetic one. A comparison of the 1973 flood event, the most dramatic ever recorded in the area, with the 2012 event, where there was a similar discharge but a sediment load deficit, reveals greater changes and a new flooding pattern and extension. In-channel gravel mining may be responsible for significant local changes in channel incision and profile. This, together with the collateral effects of aquifer overexploitation, can favor increased river velocity and stream power, which intensify the consequences of the flooding. The results obtained here clearly demonstrate an existing transition from the former alluvial pattern to a confined fluvial trend, which may become more pronounced in the future due to the time-lag between the drop in aquifer level and ground subsidence, and introduce a new scenario to be taken into consideration in future natural hazard planning in this area.

Upper limits of flash flood stream power in Europe

Geomorphology ◽  
2016 ◽  
Vol 272 ◽  
pp. 68-77 ◽  
Author(s):  
Lorenzo Marchi ◽  
Marco Cavalli ◽  
William Amponsah ◽  
Marco Borga ◽  
Stefano Crema
Keyword(s):  
Flash Flood ◽  
Stream Power ◽  
Upper Limits

HUMAN DETECTION IN SURVEILLANCE VIDEO

2014 ◽  
Vol 28 (02) ◽  
pp. 1455003 ◽  
Author(s):  
LIANG-HUA CHEN ◽  
LI-YUN WANG ◽  
CHIH-WEN SU
Keyword(s):  
Posterior Probability ◽  
Integrated Approach ◽  
Human Detection ◽  
Moving Object ◽  
Support Vector ◽  
Fourier Descriptor ◽  
Binary Classifier ◽  
Surveillance Video ◽  
Histogram Of Oriented Gradient ◽  
First Order

In this paper, we propose an integrated approach for human detection in surveillance video. In our approach, the moving object is extracted by background subtraction; and the background model is updated by the first-order recurrence filter. Then, two complementary features are extracted for moving object classification. They are contour-based description: Fourier descriptor and region-based description: histogram of oriented gradient. As the binary classifier (support vector machine) is able to provide the posterior probability, we effectively integrate two types of features to achieve better performance. Experimental results show that the proposed approach is effective and outperforms some existing technique.

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