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Hydrological regime of urban catchment is a subject of serious changes in comparison to natural catchment. Increase of storm runoff and growth of flood risk, rise the concern. Influence of land use change on storm runoff and isochrons method for assignment of hydrograph in urban catchment have been studied. Desing storm hyetograph, calculated according to Bogdanowicz method has been (1998), on calculated from maximum rainfall data and synthetic scaling method (Bogdanowicz, Stachy, 1998). Measurements in Służewiecki Stream in Warsaw have been used from years 1993, 2002, 2012. In the period 1993-2012 we observe growth of runoff coefficient, which is a consequence of increasing impervious areas. Calculated hydrographs in 3 hours duration and 8 hours duration are higher than presented by Banasik, Hejduk, Barszcz (2007), but precisely comparison is not possible, because rainfall frequency is different (10 year and 1 year).
The main goal of this article was estimation of the lag time of direct runoff in Służew Creek catchment, located in Warsaw (Poland). To calculations there were used measured data of rainfall (Okęcie rain gauging station) and data of direct runoff at the Berensewicz Pond water gauge. The IUH based on the Nash model, in which catchment is shown as a cascade of N linear reservoirs with retention parameter k of each reservoir, was used to transform effective rainfall into direct runoff. Effective rainfall of each recorded event was estimated with two methods: exponential formula and CN-SCS method. Analysis was conducted for one hydrological year (2007), for events with water level higher than 0.75 m, which corresponds with discharge about 1 cubic meter per second. As a result of this analysis, there was stated, that two estimation methods gave different output and estimated mean lag time of direct runoff for CN- -SCS method (3.77 h) was longer than for the exponential formula (3.37 h). This case study was the part of the fi rst author’s master thesis, written at the Department of Water Engineering and Environmental Restoration (Warsaw University of Life Sciences – SGGW), entitled: “Analysis of fl ood discharges in the Służew Creek catchment at the water gauge of Berensewicz Pond”.
Two flood flow hydrographs hydrographs generated by rain events of probability of acurance of 1% and duration 2 hours in a small (A = 26,9 km2) urban catchment of Służew Creek (south part of Warsaw) have been routed by detention pond of total fl ood storage of 27,100 m3. The IUH, and CN SCS methods were used to estimated the hydrographs. The infl ow to the system has been reduced by the lateral outfl ow to detention part of the pond, when the water level in the channel was over the crest of the side overfl ow, and when there were free volume in the detention space. Level pool routing (modifi ed Puls) procedure has been used for calculating the outfl ow hydrograph from the reservoir of known storage-outfl ow invariable relationship and given infl ow hydrograph. Estimated reduction of the peak fl ow has been about 10% for the smaller fl ood hydrograph (QDmax = 6,28 m3·s–1, generated by rainfall on part of the catchment), and below 3% for the larger fl ood hydrograph (QDmax = = 9,73 m3·s–1, generated by rainfall on the whole catchment).
The essencial problem of this article is reduction of flood hydrograph by the system of ponds, located in urban catchment of Służew Creek: Berensewicz Ponds, Wyścigi Pond and Służewiecki Pond. The estimations of transformation of the flood hydrographs by reservoir was made with the use of the Puls method. Flood flow hydrograph, generated by rain events of probability of 10% and duration 2 hours in part of the catchment and then in the whole catchment, has been taken into account. The infl ow to the Berensewicz Pond has been calculated from measurement infl ow-outflow. The results of computation have shown that the reduction rates of flood hydrographs by the reservoires are insuffi cient for flood protection. Only Berensewicz Pond has significant importance on reduction of the flood flow hydrograph. To improve the efficiency of work system, it is sugessted to consider a designe of hydraulic structure with bottom outflet and overflow at Służewiecki Pond. Proposed solution would be useful, especialy for big flow hydrographs, what has been confirmed by results of computation.
The main goal of this study was to evaluate the SWMM model’s (i.e. Storm Water Management Model) applicability to simulation of runoff in the Służew Stream basin (located in the southern part of Warsaw). The twelve rainfall-runoff event measured at the surveyed Rosoła profile, were used to the verifi cation of the model. In the next phase, the SWMM model was used in order to determine the probable maximum flows, caused by estimated rainfall with 100, 50, 20, 10, 2 and 1% probability.
W pracy przedstawiono porównanie chwilowych hydrogramów jednostkowych (IUH) dla małej zlewni zurbanizowanej - Potoku Służewieckiego w Warszawie, wyznaczonych według czterech metod: formuły SCS, Rao i współautorów, analogii hydrologicznej poprzez transformację hydrogramu z sąsiedniego profilu oraz pomiarów opad - odpływ. Do opisu kształtu chwilowych hydrogramów jednostkowych przyjęto dwupara- metrową funkcję gęstości prawdopodobieństwa rozkładu gamma (model Nasha), natomiast do porównania chwilowych hydrogramów jednostkowych przyjęto charakterystyki IUH: up - wielkość kulminacji (maksymalną rzędną IUH) [h-1], oraz tp - czas wystąpienia kulminacji [h]. Do porównania hydrogramów opracowanych według różnych metod wykorzystano IUH wyznaczony na podstawie danych opad - odpływ. Przeprowadzona analiza pozwala stwierdzić, iż w sytuacji ograniczonej informacji o zlewni (braku danych pomiarowych) znajduje uzasadnienie stosowanie metody wyznaczania IUH według formuły Rao i współautorów. Określone w ten sposób IUH mogą posłużyć do obliczenia przepływów maksymalnych, co ma szczególne znaczenie przy projektowaniu budowli hydrotechnicznych, komunikacyjnych oraz przy wyznaczaniu stref zagrożenia powodziowego.
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The main areas on water structures in which sediment gathers are headwater, hollows in construction and tailwater. The processes of accumulation of upstream and downstream positions develop according to duration of the object’s exploitation. This article analyses working conditions of an elongated pipeline of culvert in Potok Służewiecki stream. These conditions were examined with the aim to evaluate the degree of discharge limitation of the object by the pipeline executed below an old construction of a road culvert under Łączyny street. The object of investigation is an old culvert under Łączyny Street to which pipeline was added. In the assembly chamber, on the rout of pipeline, a rainy collector is connected to the culvert. It is characterized by high changeability of transverse sections, bed line slopes and hydraulic conditions. An old section of the culvert has the largest capacity. The trash screen is another element that considerably reduces the capacity of the object. The tendency to segregating rubble occurs in the section of culvert. The largest sediments gather in the headwater position, near the outlet – the smallest. In the stream below the object sediments have a similar material composition to the one in the upper position. The theoretical curves of longitudinal line of slope counted with formula (2) divide the area of Fig. 2 in three zones. On the left and below the curve Jn37 the accumulation zone is located, in which the movement of sediment does not occur. Above the curve Jn60 in the right the zone of intensive sediment transport appears. Among the curves Jn37 and Jn60 the transitory zone is located, correspondive to the conditions in which erosive processes begin with growing intensity of fl ow or accumulation processes, when fl ow diminishes. For the fl ows, for which the counted gradient is larger than the gradient of water surface the diffi culties with transportation of sediment through the object may occur. In the opposite situation the transportation should continue without obstacles. Exceeding this fl ow does not guarantee, however, that an intensive carrying out of earlier accumulated bed material happens. The appearing of rinsing fl ows is an accelerating factor to this process.
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