The aim of this paper is to improve and complete the results presented in a previous work published on this journal about an experimental campaign focused on the hydraulic efficiency of continuous transverse grates for draining paved areas. This type of surface drainage structure is commonly used in urban or impervious areas (public squares, airport pavements, parks, and pedestrian areas), where conventional inlets are not recommended because they are rendered ineffective by the lack of a well-defined channelized flow path and gradients capable of directing flows toward the collecting hydraulic structures. In this paper, a methodology is presented to estimate the hydraulic efficiency of nontested continuous transverse grates. Empirical expressions are proposed to relate grate hydraulic performance to flow parameters and grate geometry without the need for laboratory tests. Moreover, the spectrum of the grates was extended in terms of dimensions and hydraulic design with respect to the first study,...

Urban drainage networks should be designed and operated preferably under open channel flow conditions without flux return, backwater, or overflows. In the case of extreme storm events, urban pluvial flooding is generated by the excess of surface runoff that could not be conveyed by pressurized sewer pipes, due to its limited capacity or, many times, due to the poor efficiency of surface drainage systems to collect uncontrolled overland flow. Generally, the hydraulic design of sewer systems is addressed more for underground networks, neglecting the surface drainage system, although inadequate inlet spacings and locations can cause dangerous flooding with relevant socio-economic impacts and the interruption of critical services and urban activities. Several experimental and numerical studies carried out at the Technical University of Catalonia (UPC) and other research institutions demonstrated that the hydraulic efficiency of inlets can be very low under critical conditions (e.g., high circulating overland flow on steep areas). In these cases, the hydraulic efficiency of conventional grated inlets and continuous transverse elements can be around 10–20%. Their hydraulic capacity, expressed in terms of discharge coefficients, shows the same criticism with values quite far from those that are usually used in several project practice phases. The grate clogging phenomenon and more intense storm events produced by climate change could further reduce the inlets’ performance. In this context, in order to improve the flood urban resilience of our cities, the relevance of the hydraulic behavior of surface drainage systems is clear.

Surface drainage systems play a key role in the urban system. To assess the flow intercepted by inlets, some approaches use recent experimental campaigns or are based on orifice or weir formulas. In this work, real scale experimental campaigns are used to define discharge coefficients to provide information for practitioners and inlet manufacturers. Tested discharge values range between 25–200 l/s whereas transversal and longitudinal slopes range from 0–4% and 0–10% respectively. Three grated inlets have been analyzed obtaining values of discharge coefficients in situations for which the flow completely covers the grates. Discharge coefficient ranges for supercritical flow conditions have been obtained and the strong relationship with the upstream Froude number has been highlighted. Considering the orifice approach, the discharge values range between 0.055–0.294, 0.033–0.431 and 0.054–0.423 for the Barcelona1, Meridiana and E-25 grated inlets respectively. Conversely, for weir assumption, the coefficients range between 0.009–0.244, 0.003–0.245 and 0.006–0.286.

Pressure pipe flow conditions appear in sewer systems when flow exceeds the hydraulic capacity of the conduit, causing some outflow to be produced. In these cases, water exits through manholes and inlets causing surface flooding. According to some recent studies, the flow leaving the pressured sewer can be estimated assuming orifice flow conditions although it requires the use of proper values of the discharge coefficient in order to obtain realistic results. In this paper, an experimental approach to calculate discharge coefficients through an inlet for surcharged pipe conditions is presented. Tests were carried out using a real laboratory platform simulating a road lane. Different surcharged flows through the inlet from 10 to 50 l/s were considered. The range of the obtained discharge coefficient has been between 0.13 and 0.41 for surcharged flow from 10 l/s to 50 l/s. Sensitivity analysis demonstrated that discharge coefficients can be considered constant for any street longitudinal slope.

Due to the increasing urbanisation trend and more recurrent flood events worldwide that are affecting exposed habitable areas like underground spaces. This state-of-the-art review presents a comprehensive analysis of the available literature that focuses on defining instability criteria for hazard assessment during human evacuation of underground flooded stairs. The studies are outlined in three main groups: theoretical, experimental campaigns and numerical approaches. Several methods for defining specific criteria were found, most of these criteria were described as a function of water depth (D) alone or in combination with velocity (V) highlighting the importance of these two water-related parameters for flood-related hazard evaluation. Succinctly, the most relevant findings and limitations of these studies are discussed and summarised in tables. A comparison with other flood-related hazard criteria in plain and mild-slope areas is presented. Finally, potential future investigation lines are proposed. Thus, this state-of-the-art review could offer a comprehensive overview of the topic and stimulate new exploratory studies in this research field yielding valuable insights that can be easily transmitted to stakeholders or non-experts and foster urban resilience during floods.

Grated inlets have the normal function of collecting the surface runoff into sewer networks, but when the flow exceeds the capacity of the sewer pipes and conduits get pressurized, an outflow from the sewer manholes and grates can occur. In this case, the grate produces an energy loss in the outflow from sewer to street that could be hydraulically quantified characterizing this kind of flow. Energy loss analysis in trash racks can be found in technical literature, but no specific studies on sewer grate inlets have been found. For this reason, some experiments in full scale were developed in the hydraulic laboratory of the Technical University of Catalonia (UPC) in order to quantify hydraulic energy losses associated with flow through grated inlets during surcharging conditions. The main goal of this research work was to experimentally quantify the values of the local loss coefficient k for two different surcharged real scale grated inlets existing in Barcelona. For the tested overflows between 20 and 50 L/s, a range from 0.25 to 3.41 was observed for k coefficients under different average velocities of reference and different flow conditions.