Leaky urban drainage networks (UDNs) exfiltrating wastewater can contaminate aquifers. Detailed knowledge on spatiotemporal distributions of water-dissolved, sewer-borne contaminants in groundwater is essential to protect urban aquifers and to optimize monitoring systems. We evaluated the effect of UDN layouts on the spreading of sewer-borne contaminants in groundwater using a parsimonious approach. Due to the UDN’s long-term leakage behavior and the existence of non-degradable sewer-borne contaminants (equivalent to a conservative and constant contaminant source), we employed a concept of horizontal line sources to mimic the UDN layout. This does not require the consideration of bio-degradation processes or temporal delay and effectively bypasses the vadose zone, thus reducing computational requirements associated with a full simulation of leakages. We used a set of synthetic leakage scenarios which were generated using fractals and are based on a real-world UDN layout. We investigated the effects of typical leakage rates, varying groundwater flow directions, and UDN’s layouts on the shape of the contaminant plume, disregarding the resulted concentration. Leakage rates showed minimal effects on the total covered plume area, whereas 89% of the variance of the plume’s geometry is explained by both the UDN’s layout (e.g., length and level of complexity) and groundwater flow direction. We demonstrated the potential of applying this approach to identify possible locations of groundwater observation wells using a real UDN layout. This straightforward and parsimonious method can serve as an initial step to strategically identify optimal monitoring systems locations within urban aquifers, and to improve sewer asset management at city scale.

Urban pluvial flooding occurs when the capacity of sewer networks is surcharged due to large amounts runoff produced during intense rain events. Rapid urbanization processes and changes in climate increase these events frequency. Effective and sustainable approaches for the reduction in urban floods are necessary. Although several gray, green and hybrid measures have been studied, the influence of network structure on flood occurrence has not yet been systematically evaluated. This study focuses on evaluating how different structures of a single urban drainage network affect flood volumes and their associated damages. Furthermore, a cost–benefit analysis is used to determine the best network structure. As a case study, a sewer subnetwork in Dresden, Germany was selected. Scenarios corresponding to different layouts are developed and evaluated using event-wise hydrodynamic simulation. The results indicate that more meshed structures are associated with lower flood volumes and damage. Moreover, all analyzed scenarios were identified as cost-effective, i.e., the benefits in terms of flood damage reduction outweighed the costs related to pipe installation, operation and maintenance. However, a predominantly branched structure was identified as the best scenario. The present approach may provide a new cost-effective solution that can be integrated into the development of different mitigation strategies for flood management.

High-resolution data and continuous monitoring of water quality parameters enable a more accurate characterisation of stormwater pollutants dynamics. This article presents a unique dataset combining real-time online monitoring of turbidity and discharge data with event-based, size-fractionated chemical characterisation of stormwater. Turbidity and discharge were measured with a high temporal resolution at the stormwater outlet of a small urban catchment in Dresden, Germany. Additionally, for selected rainfall-runoff events, the following data were produced: total suspended solids concentrations and their particle-size distribution (63 µm: coarse fraction), elemental composition, and organic content. The online monitoring data covers the period from January 2018 to August 2022, whereas the sampled data were collected from September 2018 to 2021. Turbidity serves as a proxy for particles, organic, and elemental composition of stormwater. Therefore, our dataset is suitable for exploring flush dynamics, particle transport patterns, particle-bound pollutants, as well as for developing and validating particle transport formulations in urban drainage models. This will enable a more effective identification of stormwater treatment and management strategies to address different pollutant flushes, support regulatory decision-making, and minimise the impact of stormwater discharges on receiving water bodies. Hence, intended users of this dataset include, but are not limited to, the urban drainage/urban hydrology/stormwater research community and practitioners, students, decision-makers, policymakers, urban planners, engineers, and other stakeholders interested in water-related issues at the city or urban catchment scale.

During heavy rainfall events, the large amounts of generated runoff in urban areas mobilise particulate matter from different surfaces. These particles have attached other contaminants such as heavy metals, polycyclic aromatic hydrocarbons and, faecal microorganisms. In urbanised areas, particle-bound contaminants (PBCs) may reach rivers through surface runoff, combined sewer overflows or storm water discharges. This may affect the water quality of receiving water bodies and creates health risks to humans and ecosystems. Due to the spatial variability of PBCs, associated to different land uses and pollution sources, the quantification and characterisation of contaminant pathways remain a challenge. Despite high investments, the implemented management alternatives to improve river water quality are still inefficient due to late identification of pressures and lack of a real paradigm shift towards holistic approaches. Therefore, it is necessary to better understand and describe the main factors controlling PBCs pathways in urban areas. This is expected to facilitate the selection of appropriate technologies and strategies to reduce the impact of urban discharges on receiving water bodies.In this context, the aim of this study is to evaluate the influence of spatial and temporal variability of sediments and PBCs sources on river water quality in an urbanised catchment, considering land-use distribution within the sewersheds. This is expected to provide a better understanding of the relationship between drivers of relevant PBCs and the response of the urban water system under dynamic conditions (i.e. variable sediment load, urban runoff, storm water discharge and river flow). Data for this study is obtained from an integrated monitoring network in a small watershed (Lockwitzbach) located in Dresden, Germany. This urban observatory consists of four water quality monitoring stations within the stream and in the sewer network. High-resolution (1min) discharge and turbidity data are collected. This allows to understand the dynamic transport mechanisms of sediments in the catchment, providing insights in complex runoff and discharge processes.Integrated simulation of sediments and PBCs (i.e. heavy metals) is done by using EPA SWMM to evaluate surface build-up and wash-off. Additionally, the impact of sedimentation, accumulation and re-suspension of sediments and heavy metals within the sewer network and river are analysed using a simplified block developed in Simba#. Calibration and validation of the integrated model was done using online monitoring data and water samples taken during the period 2018-2020. Turbidity was used as a proxy for total suspended solids and PBCs. We identified and prioritised urban areas that are hotspots for high sediment and PBCs loads. Those represent potential locations for an optimal control and reduction of water pollution strategies. Results suggest that integrated simulation is an effective approach to analyse transport mechanisms and pathways of sediments and PBCs within urbanised catchments. Furthermore, high-resolution discharge and turbidity data are especially useful to represent the wash-off of contaminants associated to the first flush process during rainfall events.

In urbanised areas, the surface runoff generated by heavy rainfall events mobilise particles carrying contaminants such as heavy metals and polycyclic aromatic hydrocarbons. Those particle-bound pollutants (PBPs) are likely to reach streams through combined sewer overflows or stormwater discharges. Hence, stormwater runoff from urban impervious surfaces affects hydrological and sedimentological conditions of urban streams. Therefore, it is necessary to assess sediment sources, pathways and storage in urbanised catchments to improve sediment management and receiving water quality.This study aimed at characterising the impacts of urban wet weather discharges (UWWDs) along a stream bed. Thus, the intrusion of fine sediments and the concentration of heavy metals was evaluated along a downstream urbanisation gradient. Our study area is a small catchment (Lockwitzbach, 84 km2) located in Dresden, Germany. It has a main stream length of 29 km and its land use is dominated by non-irrigated arable land (40%), pastures (21%) and urban areas (14%). The urbanised area is clustered towards downstream. In this study we focused on the last 7 km within the city of Dresden, where 9 combined sewer overflows and 19 storm water outlets are located. The urban catchment was subdivided into 9 sewersheds considering the characteristics of the urban drainage network.Between March and October 2021, sediment samples were collected along the stream bed in 7 points, before and after heavy rainfall events. A total of 75 sediment samples were characterised considering 9 elements concentration (i.e., Al, B, Cd, Co, Cr, Cu, Pb, Sr and Zn) of the fine sediment fraction (<63µm), total solids and volatile solids. Additionally, suspended sediment samples were taken upstream and downstream the urban area. In those two sampling points, high-resolution discharge and turbidity data were continuously monitored. Fine sediment loads were calculated in order to compute a mass balance of the urban catchment. This allowed to understand the dynamic transport mechanisms of fine sediments and relevant PBPs in the urban stream, considering complex runoff and discharge processes.Furthermore, identification of main sources of sediments was carried out using finger-printing analysis. K-means clustering allowed to group the stream bed sediment samples into two distinct types: 1) “relatively clean sediment” and 2) “sediment affected by UWWDs”. The urban discharges increase the element concentration in the fine sediment fraction along the first 6 km of the stream. This suggests an accumulation of contaminants towards the urban gradient. However, results showed a high attenuation capacity of the urban stream, since after receiving 27 UWWDs, the elements concentration of the sediment collected in the last 1 km is statistically similar to the fine sediment collected upstream the urban area (cluster type 1).Fine sediments export was calculated for each sewershed. Areas with UWWDs carrying high sediments and PBPs loads were distinguished. Likewise, potential hotspots of intrusion of fine sediments in the stream were clearly determined. Those hotspots could be potential locations to control fine sediments and PBPs. The findings will help prioritising and locating possible strategies to improve river water and sediment quality.