Assessment method for the hydraulic efficiency of urban drainage system components

This study evaluates the performance of different retention solutions in stormwater drainage systems. The outcome of this study proposes a method to determine the hydraulic efficiency of different stormwater drainage retention components, in which instead of assessing retention capacities, the resistance time is used. The study was conducted in a laboratory setting, involving four different hydraulic units designed to increase channel retention in the drainage system. These units operate under diverse hydraulic conditions, including varying channel gradients, different inflow rates, and differential outflow reductions. The analysed units included a linear system (U1), a linear system with increased retention (U2 and U4), and a ring system (U3). The experiments conducted laid the groundwork for a method to determine the hydraulic efficiency of drainage components in situations where estimating efficiency based on the analysis of required capacities is impossible or very time-consuming. The research results were utilised to assess the hydraulic efficiency of the studied hydraulic units U1-U4. The results of this study indicated a significantly higher efficiency of ring systems (U3) under all input scenarios at the highest tested flows (12L/s). In specific cases, its application allowed for over a 5-fold extension of the system’s correct operation time, and the determined hydraulic efficiency coefficient α values ranged between 4.5 and 11.4. For lower flows (10 L/s), the most effective system varied depending on the hydraulic conditions, with the channel gradient identified as the parameter that most significantly influenced the efficiency of individual solutions.