Using hydraulic modeling techniques (e.g., one-dimensional/two-dimensional (1D/2D) hydraulic modeling, dam break scenarios) for extracting the flood settings is an important aspect of any action plan for dam failure (APDF) and flood mitigation strategy. For example, the flood hydraulic models and dam break scenario generated based on light detection and ranging (LiDAR)-derived digital elevation models (DEMs) and processed in the dedicated geographic information systems (GIS) and hydraulic modeling software (e.g., HEC-RAS—Hydrologic Engineering Center River Analysis System, developed by USACE HEC, Davis, CA, USA) can improve the flood hazard maps in case of potentially embankment dam failure. In this study, we develop a small-scale conceptual approach using 2D HEC-RAS software according to the three embankment dam break scenarios, LiDAR data (0.5 m spatial resolution), and 2D hydraulic modeling for the Başeu multi-reservoir system which belongs to the Başeu River (NE Romania) including R1—Cal Alb reservoir, R2—Movileni reservoirs, R3—Tătărăşeni reservoirs, R4—Negreni reservoirs, and R5—Hăneşti reservoirs. In order to test the flood control capacity of the Bașeu multi-reservoir system, the Cal Alb (R1) dam break scenario (piping failure) was taken into account. Three 2D stream flow modeling configurations based on R1 inflow rate with a 1% (100 year), 0.5% (500 year), and 0.1% (1000 year) recurrence interval and the water volume which can be accumulated with that specific inflow rate (1% = 10.19 × 106 m3; 0.5% = 12.39 × 106 m3; 0.1% = 17.35 × 106 m3) were computed. The potential flood wave impact was achieved on the basis of different flood severity maps (e.g., flood extent, flood depth, flood velocity, flood hazard) generated for each recurrence interval scenario and highlighted within the built-up area of 27 settlements (S1–S27) located downstream of R1. The results showed that the multi-reservoir system of Bașeu River has an important role in flood mitigation and contributes to the APDF in the context of climate change and the intensification of hydrological hazard manifestation in northeastern Romania.
The ability to extract flood hazard settings in highly vulnerable areas like populated floodplains by using new computer algorithms and hydraulic modeling software is an important aspect of any flood mitigation efforts. In this framework, the 1D/2D hydraulic models, which were generated based on a Light Detection and Ranging (LiDAR) derivate Digital Elevation Model (DEM) and processed within Geographical Information Systems (GIS), can improve large-scale flood hazard maps accuracy. In this study, we developed the first flood vulnerability assessment for 1% (100-year) and 0.1% (1000-year) recurrence intervals within the Jijia floodplain (north-eastern Romania), based on 1D HEC-RAS hydraulic modeling and LiDAR derivate DEM with 0.5 m spatial resolution. The results were compared with official flood hazards maps developed for the same recurrence intervals by the hydrologists of National Administration “Romanian Waters” (NARW) based on MIKE SHE modeling software and a DEM with 2 m spatial resolutions. It was revealed that the 1D HEC-RAS provides a more realistic perspective about the possible flood threats within Jijia floodplain and improves the accuracy of the official flood hazard maps obtained according to Flood Directive 2007/60/EC.
This research aimed to identify flooded areas following the July 2010 floods, using Landsat 7-ETM + satellite imagery and a more efficient way to extract water bodies. By computing several indices, such as MNDWI, NDWI, NDVI, AWI, WRI and NDMI, it was concluded that, in the present case, the NDWI index was most effective, the data obtained having a very good accuracy. The studied area was the Jijia River Slobozia-Dângeni sector, the Landsat 7-ETM + images were taken on July 3, 2010. The flow rate at this time at the Dângeni station was 473 cm, decreasing compared to July 1, 2010 when the share reached 579 cm. The flooded area obtained is 15.80 km2, the maximum extension of the flood area on July 3, 2010 being approx. 1 km on the localities of Durneşti and Sapoveni. The study found 143 houses in 19 localities flooded. Of the total flooded areas, the largest share is held by arable land (44.58%), with a surface area of 7.04 km2.
The Baseu catchment basin is situated in the northeast of Romanian and it is a right-side tributary of the Prut River. At the end of spring the most significant floods occur on the Romanian territory. They are due to the maximum amounts of rainfall and to snow melting. The phenomenon is also specific to the Baseu catchment basin. The last 20 years have witnessed a change in temporal manifestation, with maximum intensities during the summer (the months of July and August) when heavy rainfall is recorded. In the last 40 years, several critical episodes occurred, which endangered the lives of 79,000 inhabitants. In order to assess the hazard associated with maximum runoff, a floodable stripe with an assurance of 1% (once every 100 years) was modelled. Flood modelling involved the manipulation in GIS setting of the parameters of digital elevation model (DEM) and of their relations with the hydrological system. The main objective of the study is the modelling of an exceptional flood with a probability of 1%, similar to the one of 1969, when the Stefanesti gauging station recorded a flow of 330 m 3 /s. Based in the analysis of the hydrological data spanning over 50 years, recorded at three gauging stations, a maximum flow of 248.1 m 3 /s was determined (the Stefanesti gauging station), using the Pearson III probability curve. The findings have highlighted the significant vulnerability of the human settlements situated in the flood plain of the Baseu River. A surface of 17,000 ha would be flooded, accounting for around 17.5% of the total basin surface.
Storage lakes represent an important source of water for the areas with a high deficit of hydrologic balance (ex: Moldavian Plain from NE of Romania). This region holds an important number of lakes that allow the storage of water during periods with rainfall shortage. At the same time, they play an important role in the protection of localities against floods. In addition to the benefits that these lakes have, they can also represent a risk factor for the localities situated in the downstream region, in case of dam collapse. In Romania it is widely known the catastrophic event from 1991 when Belci Dam situated on Tazlău River was breached, causing an entire neighborhood from Onesti City to be flooded. The present study focuses on Catamarasti Lake which has a maximum water volume of 12 million cubic meters, the dam being located 3 km upstream of the first locality and the periphery of Botosani City. The proximity of the inhabited areas makes the dam break scenario to be a probable event, therefore the identification of the propagation time of a possible flood wave is essential towards the creation of a system for the protection of the population. The dam break simulation and the quantification of the propagation time of the entire water volume on Sitna river valley is made using HEC-RAS, based on a LiDAR digital elevation model, using the 2D simulation method. In this case, having a likely floodable surface as well as the time in which the flood can reach the nearby localities, there were identified the risk exposed households located in the floodplain, in the vicinity of the river.
Storage lakes represent an important source of water for the areas with a high deficit of hydrologic balance (ex: Moldavian Plain from NE of Romania). This region holds an important number of lakes that allow the storage of water during periods with rainfall shortage. At the same time, they play an important role in the protection of localities against floods. In addition to the benefits that these lakes have, they can also represent a risk factor for the localities situated in the downstream region, in case of dam collapse. In Romania it is widely known the catastrophic event from 1991 when Belci Dam situated on Tazlău River was breached, causing an entire neighborhood from Onesti City to be flooded. The present study focuses on Catamarasti Lake which has a maximum water volume of 12 million cubic meters, the dam being located 3 km upstream of the first locality and the periphery of Botosani City. The proximity of the inhabited areas makes the dam break scenario to be a probable event, therefore the identification of the propagation time of a possible flood wave is essential towards the creation of a system for the protection of the population. The dam break simulation and the quantification of the propagation time of the entire water volume on Sitna river valley is made using HEC-RAS, based on a LiDAR digital elevation model, using the 2D simulation method. In this case, having a likely floodable surface as well as the time in which the flood can reach the nearby localities, there were identified the risk exposed households located in the floodplain, in the vicinity of the river.
The European Network of Experimental and Representative Basins (ENERB) is the results of several experimental projects concerning the hydrological forecasting and flood mitigation effort which have been implemented within states member of European Union. In Romania, the hydrometric activity for ENERB it is currently composed of 14 representative basins (RB) of which the Trebeş-Negel (184 km2) was selected as RB for Eastern Carpathian and Subcarpathian transition zone. Located in one of the most affected territories by hydrological hazards, the Trebeş-Negel RB reacted as a small-scale flood sensor for the entire region. Using the well-documented discharge and pluviometric database collected at five gauge stations within the study area, we develop the first comparative analysis of historical flood events that occurred in the Trebeş-Negel RB post-1990. Five exceptional floods were selected: flood events from July 2 to July 8, 1991; flood events from June 16 to June 22, 1992; flood events from July 11 to July 14, 2005; flood events from July 26 to July 31, 2010; and flood events from June 28 to July 1, 2018. All flood events envisaged were caused by heavy rains, when significant amounts of precipitations were recorded which sometimes exceeded 100 mm/day.
One of the climatic hazards experienced in recent times is the drought that affects the society and the ecosystems. This study is intended to identify the statistically significant trends in the minimum flow characteristics and hydrological drought episodes, during five years, of the Trebes-Negel representative river basin, located in the Moldavian Sub Carpathians, in Romania. It is an important hydrological objective used for research purposes, considered as a reference point for all small basins with an identical natural environment. Data analysis revealed that drought is recorded at two of the 6 hydrometric stations analyzed (Podis and Magura) in 2015, starting in August and ending with October.
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