This study analyzes the possibilities of using an irrigation sluice gate in submerged conditions to measure water flow rate. Hydraulic experiments on sluice gate discharge capacity were performed on a model made on a 1:2 scale. Measurements were taken for the submerged flow of the sluice gate. Nomograms and relationships for discharge coefficients of the analyzed sluice gate were developed. The possibility of using the existing nomogram for discharge capacity of the submerged sluice gate to determine the discharge capacity of the modeled gate was also investigated. The effect of narrowing of the sluice gate cross-section resulting from different mounting techniques on its capacity was explained. The analyses confirmed the possibility of using the formulas for the submerged sluice gate to estimate the flow through the irrigation sluice gate.

Urbanization and climate change have resulted in an increase in catchment runoff, often exceeding the designed capacity of sewer systems. The decision to modernize a sewer system should be based on appropriate criteria. In engineering practice, the above is commonly achieved using a hydrodynamic model of the catchment and the simulation of various rainfall events. The article presents a methodology to analyze the effect of rainfall characteristics parametrized with intensity-duration-frequency (IDF) curves in regard to performance measures of sewerage networks (flood volume per unit impervious surface and share of overfilled manholes in the sewerage network) accounting for the model uncertainty determined via the generalized likelihood uncertainty estimation (GLUE) method. An urban catchment was modeled with the Storm Water Management Model (SWMM). Analyses showed that the model uncertainty exerts a large impact on certain measures of sewage network operation. Therefore, these measures should be analyzed in similar studies. This is very important at the stage of decision making in regard to the modernization and sustainable development of catchments. It was found that among the model parameters, the Manning roughness coefficient of sewer channels yields a key impact on the specific flood volume, while the area of impervious surfaces yields the greatest impact on the share of overflowed manholes.

Stormwater reservoirs are used to control the runoff volume and to attenuate the peak flow rate from urban catchments. The required capacity of a stormwater reservoir and its dimensions are calculated with the help of rainfall-runoff models, using a time series of observed rainfall or a design rainfall. However, many studies have revealed that the reliability of models of urbanized basins is far from perfect. This study presents an optimization of the capacity of a stormwater reservoir in a small urbanized basin, taking into account the predictive uncertainty of the rainfall-runoff model. An analysis of the model uncertainty using the generalized likelihood uncertainty estimation (GLUE) framework allowed for an assessment of the optimal capacity of the stormwater reservoir required to ensure a given safety level. Such a probabilistic approach is compared with a deterministic approach, which is commonly used in practice, where the effect of uncertainty of the rainfall-runoff model is usually neglected. The numerical experiment showed that stochastic and deterministic approaches are not equivalent as the calculated capacities of the reservoirs were different. The deterministic solution leads to an overestimation of the reservoir capacity from 20 to 150%, compared to the mean capacity obtained using a stochastic formulation. The results indicate that the uncertainty of the runoff model might potentially be a significant factor in stormwater reservoir design.

The derivation of the flood risk maps requires an estimation of maximum inundation extent for a flood with a given return period, e.g. 100 or 500 yr. The results of numerical simulations of flood wave propagation are used to overcome the lack of relevant observations. In practice, deterministic 1-D models are used for that purpose. The solution of a 1-D model depends on the initial and boundary conditions and estimates of model parameters based on the available noisy observations. Therefore, there is a large uncertainty involved in the derivation of flood risk maps using a single realisation of a flow model. Bayesian conditioning based on multiple model simulations can be used to quantify this uncertainty; however, it is too computer-time demanding to be applied in flood risk assessment in practice, without further flow routing model simplifications. We propose robust and feasible methodology for estimating flood risk. In order to decrease the computation times the assumption of a gradually varied flow and the application of a steady state flow routing model is introduced. The aim of this work is an analysis of the influence of those simplifying assumptions and uncertainty of observations and modelling errors on flood inundation mapping and a quantitative comparison with deterministic flood extent maps. Apart from the uncertainty related to the model structure and its parameters, the uncertainty of the estimated flood wave with a specified probability of return period (so-called 1-in-10 yr, or 1-in-100 yr flood) is also taken into account. In order to derive the uncertainty of inundation extent conditioned on the design flood, the probabilities related to the design wave and flow model uncertainties are integrated. In the present paper that integration is done whilst taking into account the dependence of roughness coefficients on discharge. The roughness is parameterised based on maximum annual discharges. This approach allows for the relationship between flood extent and flow values to be derived, thus giving a cumulative assessment of flood risk. The methods are illustrated using the Warsaw reach of the River Vistula as a case study. The results indicate that deterministic and stochastic flood inundation maps cannot be quantitatively compared. We show that the proposed simplified approach to flood risk assessment can be applied even when breaching of the embankment occurs, with the condition that the flooded area is small enough to be filled rapidly.

Specific flood volume and degree of flooding are important parameters for evaluating the performance of stormwater networks. Hydrodynamic models are usually used to calculate these important measures, but this task requires the collection of detailed data on land use, the sewer network, rainfall, and flows, which are not always possible to obtain. The present research consists in the development of a methodology, using the USEPA Stormwater Management Model (SWMM), for simulating the performance of a stormwater network to determine whether it is in need of modernization. This determination is based on independent variables including rainfall data, catchment retention, and channel capacity. A logistic regression was developed to assess the sewer network performance based on simulation of specific flood volume and degree of flooding in the context of modernization. An extended sensitivity analysis was also used to assess the influence of rainfall intensity on the results of sensitivity coefficient calculations for the calibrated SWMM parameters. Using the extreme gradient boosting method, a tool has been developed to optimize the combination of SWMM parameters, reducing the uncertainty of simulation results, which can be used in the selection of their measurement methods prior to model development. It has been shown that, using the logistic regression model, it is possible to rapidly simulate the operation of a stormwater system to assess its need for modernization. It was confirmed that an increase in rainfall intensity leads to a significant decrease in the values of the calculated sensitivity coefficients associated with the SWMM parameters. The highest sensitivity coefficient was shown for a correction coefficient for percentage of impervious areas; for rainfall intensity $33–133\mathrm{L}·{(\mathrm{s}·\mathrm{ha})}^{-1}$ varied from 1.45 to 12.38. This result leads to a method for selecting specific rainfall events for calibration of the model, thereby improving the ability to assess the performance of the stormwater system. Interestingly, however, for the exemplary catchment in Kielce, Poland, the generalized likelihood uncertainty estimation (GLUE) method was used, combined with the XGboost machine learning technique, to determine that the reliability of the SWMM parameters has a negligible impact on the probability of a stormwater network failure.