The paper presents an assessment of the applicability of HEC-HMS programme to simulate a precipitation flood event in an ungauged basin. The programme has been developed by the Department of the Army Corps of Engineers and enables conducting hydrological calculations for basins with different characteristics and including a number of meteorological factors. The application of this model in Polish conditions was verified in the basin of the Stobnica River - a right tributary of the Wisłok River. The calculations were carried out for the flood event caused by a continuous rain, which occurred in April 1998. Four hydrological models were compared: geomorpho-climatic instantaneous unit hydrograph by Nash - GcIUH_Nash, Snyder's synthetic unit hydrograph with the determination of parameters by regression models - Snyder_reg and standard method - Snyder_ stand and Clark's instantaneous unit hydrograph - IUH_Clark, where the model parameters were optimized in the programme. The calculations revealed that the best simulation results were obtained with the Snyder_stand and Snyder_reg models. Further research should be directed to verifying the applicability of HEC- -HMS programme for hydrological analyses of much more extensive hydrometric material and basins with different characteristics.
Comparison of quality of Snyder’s model for determination flood waves was examination in this work. Model parameters were calibrated based on objective functions: percentage error in peak flow (PEPF), percentage error in volume (PEV), peak-weighted root mean square error (PWRMSE), sum of absolute residuals (SAR) and sum of squared residuals (SSR). Quality of model was calculating by Nash-Sutcliffe efficiency coefficient E. Additionally sensitivity of a model was characterized by its flexibility. The analyses were performed in the watershed of Grabinka. It has been found that the use PWRMSE as the objective function allows to obtain the best quality results of simulation. Furthermore, Snyder’s model is flexible to the change of Cp coefficient.
Andrzej Wałęga, Dariusz Młyński and Katarzyna Wachulec
The aim of the study was to assess the applicability of asymptotic functions for determining the value of CN parameter as a function of precipitation depth in mountain and upland catchments. The analyses were carried out in two catchments: the Rudawa, left tributary of the Vistula, and the Kamienica, right tributary of the Dunajec. The input material included data on precipitation and flows for a multi-year period 1980–2012, obtained from IMGW PIB in Warsaw. Two models were used to determine empirical values of CNobs parameter as a function of precipitation depth: standard Hawkins model and 2-CN model allowing for a heterogeneous nature of a catchment area.
The study analyses confirmed that asymptotic functions properly described P-CNobs relationship for the entire range of precipitation variability. In the case of high rainfalls, CNobs remained above or below the commonly accepted average antecedent moisture conditions AMCII. The study calculations indicated that the runoff amount calculated according to the original SCS-CN method might be underestimated, and this could adversely affect the values of design flows required for the design of hydraulic engineering projects. In catchments with heterogeneous land cover, the results of CNobs were more accurate when 2-CN model was used instead of the standard Hawkins model. 2-CN model is more precise in accounting for differences in runoff formation depending on retention capacity of the substrate. It was also demonstrated that the commonly accepted initial abstraction coefficient λ = 0.20 yielded too big initial loss of precipitation in the analyzed catchments and, therefore, the computed direct runoff was underestimated. The best results were obtained for λ = 0.05.
Artur Radecki-Pawlik, Andrzej Wałęga, Jakub Wojkowski and Jacek Pijanowski
Along the paper the size of peak runoff was assessed affected by the influence of changes in water catchment area by land use due to future planned agricultural changes. The investigations were conducted in the Winna Góra catchment area located in Mściwojów, Lower Silesian voivodship at the Mściwojów water reservoir. At present, the catchment is used as arable land, forest and meadows. In the future the area of sealed surfaces such as: roofs, roads and car parks will increase. This can contribute in the change of water balance components. Analyses has shown, that changes in the use of a catchment area lead to reduction of surface flow time from the catchment (less resistance to motion) - in effect it causes increase of the runoff volume at about 28%. The increase of the water runoff volume may have significant influence on the Winna Góra development and functions as well as volume of water run into the Mściwojów water reservoir. To counteract the results of adverse changes caused by the catchment sealing - it is recommended for the investigated area to apply a balanced approach. This would consist of retaining precipitation water in its place of origin.
Izabela Pietrusiewicz, Agnieszka Cupak, Andrzej Wałęga and Bogusław Michalec
The paper presents the results of using two models: a conceptual model of Wackermann and a NRCS-UH synthetic unit hydrograph, for flow calculation in uncontrolled catchment of the Słonka, Poland. These models were chosen because of simplicity of models’ parameters evaluation, what is important from engineering calculation point of view. Flows with the probability of exceed amounting to 0.5%, 1%, 2%, 5%, 10%, 20%, and 50% and for different levels of the catchment moisture were evaluated.
The flood waves generated in the Wackermann model were characterized by a short duration (over 2 hours), shorter concentration time (about 1 hour), and by about 70% higher peak flow values than those generated using the NRCS-UH method. A common feature of both methods were higher values of peak flows for the third level of the catchment moisture, as compared to the second level. It is also worth noticing that in both methods no flood wave was generated for the probabilities of 10, 20 and 50% and for the second level of the catchment moisture. It was assumed that hydrographs made with use Wackermann model better describe flood wave in mountain river, which Słonka is.
The objective of the research was to look into the role that bioretention systems play in a decentralized management of stormwater runoff from the impervious areas. The study took place at a catchment of a low permeability and equipped with a combined sewer system. Two rainfall options were selected: actual rainfall intensity q = 105.65 dm3∙s−1∙ha−1 and a hypothetic rainfall with a probability of exceedance p = 10% and q = 40.7 dm3∙s−1∙ha−1. All calculations were carried out using the SWMM EPA program (storm water management model; Environmental Protection Agency). They have shown that the bioretention system reduces the cumulative flow rates by over 55% and the flood wave volume by over 54%. Moreover, it was found that, a precipitation pattern significantly influences runoff from the urban catchment.