The water movement of the sewer collectors is of a non-permanent type because of the variation in flow over time. Non-permanent movement in collectors is mathematically modelled by the Saint Venant equations. To solve the equation system, the characteristic method was used, provided that both equations are quasi-linear in the unknown h and Q. Non-dynamic contouring conditions are given by the hydraulic feature of the collectors / tanks located on the collector. Dynamic contour conditions are rendered by the collector-specific equations (river level effluent hydrograph, manoeuvring parameters of the boiler, manoeuvring characteristics at pumping stations, etc.). For the mathematical model implementation, a computational program was developed in the Matlab programming environment (Variation Gradual Collector Program). The program was used to simulate the non-permanent movement in the main sewerage collector “Cacaina” from the sewerage network of the city of Iasi. The simulation of the non-permanent movement was done in two collector evacuation scenarios (gravity and pumping). The analysis of the results obtained for scenario 2 highlights the differential operation of the eight collector sections separated by the side feeders. Simulation of the movement has highlighted the exceeding of the minimum and maximum values of the parameters imposed by the operating rules.

Abstract:The paper presents an analysis of the high hydrological risk phenomena formed in the hydrographic basin of the Trotuş River in the last period of time. The Trotuş River and the tributaries are monitored by 21 hydrometric stations. Precipitation volume processing indicated a number of risk factors that have prevailed over the last 20 years. The hydrological data processing revealed the presence of several flood flows in the same year. The effects of the floods have materialized through the excessive degradation of river bedside regulation and shore defence works. The floods of the past 25 years have resulted in the destruction of a large number of economic and social objectives in the Trotuş River area, as well as human losses. Parameters of hydroclimatic risk highlighted by research are represented by torrential precipitations, floods with high probability, high frequency of high-flow flows, formation of high erosion velocities of the bed, etc. Parameters of hydroclimatic risk impose special conditions for the design of river regularization and shore defence.

Research has analyzed components of the climate and hydrological regime on the Trotuş River and its tributaries over the past 30 years. The hydrological risk was determined by natural causes, but also by anthropogenic causes. Parameters of hydroclimatic risk are represented of the torrential rainfall, flood flows, high frequency of high flows, high erosion speeds etc. The research revealed that at very low intervals (3-5 years) there were floods with very high flows. Changing the climate regime (precipitation concentration on small days) and the natural relief forms in the hydrographical basin (the Eastern Carpathian Mountains) allowed natural risk to occur in the hydrological regime of the Trotuş River. Anthropic factors, in particular, the modification of the leakage coefficient by deforestation of forests and the change of agricultural use of land with large slopes have contributed to the occurrence of anthropogenic risk in the Trotuş River basin. Corroboration of the two types of risk, natural and anthropic, has led to a hydrological disaster regime in the Trotuş River Basin.

The paper presents the studies and researches on the natural and anthropic risk parameters on the Moldova riverbed in the Soci area, Iasi County. In this area are located hydrotechnical structures for regulation of the riverbed and shore defence for the protection of the undercrossing of the Timisesti-Iasi adduction pipeline. The theoretical study analyzed hydrological risk parameters (especially liquid and solid flows) recorded over the last 30 years. High flow rates have a high hydroclimatic risk for bed and river construction. Anthropogenic risk parameters were manifested in the morphological modification of the minor riverbed of the Moldova River. An important anthropogenic risk is the uncontrolled exploitation of the ballast in the bed and river banks of Moldova. The effects of this risk contributed to the descent of the bed of the bed at an accelerated pace, along with the erosion of the banks. The accumulation of the effects caused by the natural and the anthropic risks led to important morphological changes in the riverbed of Moldova. These modifications have altered the safety state of the construction of the undercrossing of the Timisesti-Iasi adduction pipeline. The result of the hydrological and also human actions was the degradation of the pipelines until their rupture.

The paper presents the current way of elaboration of the topographical and cadastral documentation needed in the process of tracking the behavior of hydrotechnical constructions such as earth dam. The studied area is represented by the accumulation of Pârcovaci located in the Deleni territorial administrative unit in Iași county. Using topo-geodetic measurements the magnitude of the vertical displacement of the studied construction were determined. The measurements were performed during the exploitation period of the dam, during 23 series of observations. Thus, there were highlighted the displacements of landmarks located on coping dam, downstream slope and outlet tower. Charts of evolution over time of vertical deformation have been made according to field observation. Also, the suface of the land corresponding to the whole of the accumulation of Pârcovaci was registered at Office of Cadastre and Real Estate Advertising Iași, through first registration documentation. This has made precise spatial delimitation of the set of lands and construction of studied area, and the whole land was recorded in the land book by assigning a unique cadastral number.