Floods are the most destructive natural phenomenon, by the total number of casualties, and value of property damage, compared to any other type of natural disaster. However, some of the most destructive flash floods are related to dam breaches or complete collapses, that release the large amounts of water, affecting inhabited areas. Worldwide, numerous dams have almost reached or surpassed the estimated construction life span, and pose an increasing risk to structure stability. Considering their continuous degrading state, increasing rainfall aggressiveness, due to climatic changes, technical error, or even human error, there are numerous, potential causes, for which dams could develop breaches and completely fail. This study aims to portray a comparative perspective of flood impact, with real-life consequences, measured by quantifiable parameters, generated from computer simulations of different breach sizes. These parameters include the total flooded surface, water velocity, maximum water depth, number of affected buildings, etc. The analysis was undergone by means of HEC-RAS based 2D hydraulic modeling and GIS, depending on high-accuracy Lidar terrain data and historical hydrological data. As a case study, Drăcșani Lake with the associated Sulița earthfill embankment dam was chosen, being one of the largest and oldest artificial lakes in Romania.

Drought with its occurrence and manifestations at all levels of the natural components, yields both direct and indirect negative effects, on the ecological systems, water resources, social, as well as economic aspects of life. Therefore, any analysis that concerns this phenomenon, must be carried out at a multi-scalar level, addressing all manifestation levels (meteorological, hydrological, and hydrogeological drought). Standardized evaluation indices (for precipitation-SPI, evaporation-, -SPEI, streamflow-SDI and groundwater-SGI) have been used to analyze the evolution of the drought phenomena in Eastern Romania, for 1, 3, 6 and 12 months’ time-scales, applied to seven groundwater bodies. The results of the analysis complement the observations concerning the evolution of meteorological drought (using SPI and SPEI) in the East European region, by highlighting the drought sequences of the last two decades of the last century. Those are accompanied by the meteorological drought sequences which occurred on extensive areas, starting from 2007, until present, with direct effects in river discharge and increases in groundwater level depths. The Bravais–Pearson correlation coefficient shows a close connection between meteorological and hydrological drought (r ~ 0.45 to 0.68) and between hydrological and groundwater drought (r ~ 0.42 to 0.74) for wells with piezometric level under 5 m depth. In the larger context of climate scenarios which envision an increase in air temperature, and a decrease in the atmospheric hydrological input, the increase in the drought frequency is obvious, with direct effects on all-natural components that are dependent on the hydrological resources.

Concentration of time (Tc) is a frequently used parameter in the evaluation of the hydrological response of different sizes hydrographic basin in case of rainfall events. The present study is innovative, because it has created an index that identifies the small‐sized hydrographic basins that are exposed to the risk of flooding. The Moldavian Plain is an area located in the northeast of Romania where the local population is frequently affected by floods and flash floods caused by heavy rainfall events. The main purpose of the current study is to identify the settlements located in the small‐sized hydrographic basins, which are associated with low concentration times and powerful surface runoff. The empirical method was applied in order to calculate the Tc for rainfall water, for each drainage basin, for a time class less than 6 hr. Calculations of the runoff water were also done for a theoretical extreme precipitation event, corresponding to the 1% occurrence probability. A total number of 312 basins were identified that are smaller than 30 km², out of which 112 have Tc of less than 6 hr. These basins, in particular, pose flood risk for 12.4% of the villages and towns in the study area.

Groundwater resources from a region may be subject to complex human and climatic pressure. The present study tries to analyze the human and climatic pressure on the groundwater resources from the eastern part of Romania, between 1983 and 2017, for seven groundwater bodies. Two parameters, the groundwater exploitation index (GWEI) and the Standardized Groundwater Index (SGI) for identifying hydrogeological droughts, were used to assess human and climatic pressure. The high values of GWEI show a significant increase in human pressure on water resources in recent decades, in lower and more populated areas, from the south and north part of de region, amid increasing investment in agriculture. In the case of climate pressure, the SGI values show significant values for the years 1983, 2000, 2007, and 2012. However, the overlap of hydrogeological droughts with an increase in human pressure can have a significant impact on the groundwater resources from this region, with negative effects in the mid and long term, under the growing effects of the regional climate changes.