Conference Agenda

The sediment accumulation in urban drainage systems can reduce their hydraulic capacity. The installation of sediment monitoring equipment is very limited due to economic and technical factors, such as the high price of existing solutions or the low coverage of these systems for data transfer. This study presents the long-term monitoring of sediment accumulation in six gully pots using temperature-based devices across two urban catchments in Zurich (Switzerland). The monitoring campaign aimed to evaluate the performance of MONTSE devices under real-world conditions, considering seasonal temperature variations. Results showed high accuracy in sediment depth estimations, with mean errors of less than 20 mm compared to in-situ measurements, as well as maximum accumulation rates ranging from 9 to 35 mm/day. Therefore, continuous monitoring combined with prior experiences on sediment accumulation is proposed as an optimal strategy to ensure the optimal operation of urban drainage systems.

The study focuses on the Fossolo catchment in Bologna, which has been the subject of various modelling studies over the years. While previous research has focused on parameter optimization, limited attention has been devoted to model structure and boundary conditions.

The study aims to investigate if the hypothesis of independence of subsystems is valid under extreme events. Two classes of models are developed in EPA-SWMM: one reflecting the original system structure and another based on a re-analysis of the system that incorporates downstream conditions. Sensitivity analysis reveals that downstream conditions impact parameter sets during extreme events, with pipe and impervious surface roughness being the most sensitive parameters.

Designing urban drainage elements can be done by setting criteria for four components: 1) proper planning horizons, 2) indicators to limit the solution space, and 3) an unambiguous calculation method with 4) corresponding input data that together encompass the solution space. Design is then a relatively simple exercise of optimizing against a set of criteria such as economy and technical feasibility. Numerous UDM conferences have discussed these criteria and in particular which modelling principles could best be used to address a given problem. We have over the past years observed this paradigm being challenged. We discuss the challenges by considering the simplest possible urban design problem: designing a retention pond for storm water for an acceptable overflow frequency. Given that we in the small country of Denmark have more than 4000 retention ponds this should be easy. However, we find that we have reached a point where it is very difficult to be able to develop and apply design tools primarily because development of a training data set with corresponding objective function is impossible.

Nested urban catchments, which are smaller catchments embedded within larger ones, exhibit hydrological and hydraulic similarities. These shared characteristics suggest the possibility of transferring parameter sets between catchments. This study, conducted in an urban catchment in Luleå, Sweden, investigated the transferability of calibrated model parameter sets across nested catchments using the Storm Water Management Model (SWMM). The results demonstrate that parameter sets calibrated for one nested catchment can be effectively transferred to others. The transferred parameter sets achieved a Nash-Sutcliffe Efficiency (NSE) of up to 0.97, indicating satisfactory reproduction of catchment flow and transferability.

Accurate hydrological modelling can be challenging in heterogeneous urban catchments, especially in regions with limited data. SWMM configurations were set up for two urban catchments in South Africa to test the performance of this model for urban areas in developing countries. Despite the relatively small catchment sizes, inconsistencies are evident between observed rainfall and measured runoff for most events. Model scenarios were created with various sets of parameter values, first from literature and then from values physically measured in the catchments. The observed and simulated flow comparisons were improved by incorporating model parameter values derived for this study, although the results were inconsistent. As the region experiences storms with considerable spatial distribution, the flow gauging stations sometimes record runoff which does not correspond to an observed rainfall event with corresponding intensity, and vice versa. Recommendations are made for further improvement of the modelled results using radar data for significant rainfall events and incorporating storage areas throughout the catchments to simulate unintended attenuation.

Sewer network hydraulic monitoring is predominantly undertaken with velocity and / or depth sensors recording data at fixed locations. Tracing in sewer networks can be used to collect additional information about the network hydraulics to better understand travel times and therefore velocities between monitoring locations, Fig. 1. The collected data can be used for source localisation (Sonnenwald et al., 2023) and to quantify mixing and dispersion. Tracing in sewer networks can be challenging due to the constituents of the wastewater and potential for ragging of instruments. This paper presents details of a cost-effective technique for sewer tracing using Rhodamine WT as a tracer, with in-situ tethered fluorometers directly measuring concentrations (PME, 2024). This has been successfully applied to studies in UK and Denmark, revealing discrepancies between model predicted and measured travel times, Fig. 2. Practical considerations in performing successful field studies will be highlighted and a summary of findings presented.