(Collaborative Early Warning Information Systems for Urban Infrastructures)
COLABIS will design and implement a Web platform that enables and eases the development of urban early warning systems, specifically focusing on information fusion derived from sensors, crowdsourcing, geosimulations, as well as administrative and historical data. The project focusses on local heavy rain, flooding and cascading events affecting urban water and sewage infrastructures but also traffic infrastructures. Pilot applications serve as proof-of-concepts and help to develop best practices. To support decision makers with timely and value added information, input data from various sources need to be combined. This data fusion comprises data retrieval, enhancement, harmonization, similarity measures, matching, conflict detection and resolving. The consistency and reliability of results essentially relies on the underlying data quality, which varies over the different data sources. Therefore, quality metrics will play a major role in COLABIS.
Architecture sketch of the COLABIS platform.
The city of Dresden will be the project’s pilot area. Findings from the BMBF-funded project REGKLAM indicate an increasing risk of local heavy rain events in the Dresden area, especially during summer seasons. These heavy rain events paired with previous dry seasons are expected to extremely stress the Dresden sewer system and provoke serious surcharges and local floods with cascading effects on the urban environment and the urban infrastructure. In this context COLABIS will develop a decision support platform for environmental agencies and sewage management companies to
better monitor, model and predict combined wastewater quantities,
better assess its pollution levels during heavy and moderate rainfall events, and
support the related decisions which water to retain, to discharge or treat right away.
The monitoring will be supported by modern sensor technology and crowdsourced data. The potential of the newly developed approaches to assess water pollutant levels will get evaluated using simulation-based techniques and data about historical events.
For pilot use cases, the Stadtentwässerung Dresden GmbH - one of the COLABIS stakeholders - represents the local sewage management company. Environmental agencies are represented by the Saxon State Office for Environment, Agriculture and Geology.
In Dresden, as in most German cities, combined sewer systems are in use, which mix sewage and stormwater to combined wastewater. In the event of heavy rains the capacities of the urban sewage plants are often insufficient to treat the total combined wastewater influx. In this case, to protect the sewage plant from overloading, water will also be discharged as diluted, but untreated sewage (e.g. into the river Elbe in Dresden) after the combined water storage volumes are exhausted (cf. figure below). This concept is known as combined sewer overflow (CSO). In controlled systems, the overflow is minimised by temporary storing combined water either in storage tanks or in large sewers which are not yet used to their full capacity. Though this approach reduces untreated combined water outflow, it is not ideal in regard to minimizing water pollution and reducing threats to the environment. As in some scenarios the retention storage will be filled with less polluted combined water (e.g. during night time) instead of the following, potentially higher polluted water (e.g. early in the morning). Depending on the sewage and rain water sources, the time of day, the duration of the preceding dry period and the course of the rain event, the pollution of the combined wastewater differs highly dynamically during the course of the event.
Overview on the COLABIS case study.
As it is the objective of the sewage system management to minimize water pollution, it should release less polluted water as combined wastewater overflow and direct the higher polluted water directly to the sewage plant or delay treatment by using less filled sewage tunnels as retention storages. Controlling about which water to be treated and which water to be discharged without treatment is currently limited. To enable a more efficient control – being based on the present level of pollution in the water – the sewage system has to act anticipatorily and not just react to the present level of water pollution.
To meet these requirements, a variety of data from different sources has to be collected and fused to enhanced information. Currently, there is a lack particularly in terms of monitoring and modelling of spatial and temporal information about stormwater and combined wastewater pollution. The spatio-temporal resolution of pollutant deposition differs by source (traffic, industry and washouts e.g. from buildings), and the knowledge about extent and dynamics of surface erosions of different pollutants is insufficient. To estimate retention effects in dependence of rain events of the immediate past, evaporation and exact surface structures of catchment areas are key factors to deduce the fill factor of water pools (like puddles, irregularities and gaps on the surface) to start the rainfall discharge modelling.
Traffic causes pollutant deposition on the road surface, e.g. by tire abrasion, brake pad abrasion (mainly copper and cadmium) and particulate matter, which will end up in the sewage system after rain events. Another source for rain water pollutants are dissolved tin and copper from roofs, eaves and down pipes, and washed off fungicides from storefronts. Further, sewage changes its composition throughout the day almost systematically and adds to the pollution of the combined wastewater. In addition to organic input and nutrient matter, sewage contains increasing amounts of anthropogenic micro pollutants.
The Dresden wastewater system is particularly suitable for the investigations, since it exhibits a good potential for monitoring and control. The Dresden sewer system has a total length of 1730 km, including combined as well as sewage and stormwater sewers. Rain intensities are measured with 20 rain gauges in 5 minutes time steps, allowing for a decent resolution of rain patterns in space and time. Some 60 water level and velocity on-line sensors are distributed in the total sewer system and at ten sites devices can be activated for event-dependent control of the runoff process. With some 80 pumping stations and five retention tanks further options for monitoring and control are available.
Apart from the sewer system monitoring, COLABIS can also built on the traffic management system VAMOS which provides a comprehensive overview on the traffic situation of the city of Dresden. Information is derived from observations of different kinds of mobile and in-situ sensors. One important source of traffic data are Floating Car Data (FCD) which are collected by more than 500 taxicabs, operated by the Dresden taxicab cooperative. By sending their position information every 5 seconds, they cover a big part of the road network and can be used to derive information about traffic density and traffic behaviour as a source to derive related pollution and depositions. The information will be further enriched by usage of a recently developed low cost in-car sensor system (enviroCar) to also include crowdsourced observations. In return early warnings generated in COLABIS applications can be issued via VAMOS, for instance to inform about blocked roads or to redirect major traffic streams by use of modern traffic signs.
The project started on 1 June 2015 and will run for 3 years.