Abstract
Abstract Tunnels are increasingly used worldwide to expand the capacity of urban drainage systems, but they are difficult to monitor with sensors alone. This study enables soft sensing of urban drainage tunnels by assimilating water level observations into an ensemble of hydrodynamic models. Ensemble-based data assimilation is suitable for non-linear models and provides useful uncertainty estimates. To limit the computational cost, our proposed scheme restricts the assimilation and ensemble implementation to the tunnel and represents the surrounding drainage system deterministically. We applied the scheme to a combined sewer overflow tunnel in Copenhagen, Denmark, with two sensors 3.4 km apart. The downstream observations were assimilated, while those upstream were used for validation. The scheme was tuned using a high-intensity event and validated with a low-intensity one. In a third event, the scheme was able to provide soft sensing as well as identify errors in the upstream sensor with high confidence.
Highlights
Tunnels are increasingly integrated in urban drainage systems (UDSs)
It is a case-specific procedure but should satisfy some general criteria: (i) the inner model should include the smallest number of structures besides the tunnel itself, to minimize the computational cost; (ii) the inner model should include all locations with sensors whose data is relevant for the assimilation; (iii) at the tunnel inlets, the boundaries should be set at locations where no backwater effects from the tunnel are expected, e.g. overflows; (iv) the outlet should include only the structures necessary to simulate the emptying of the tunnel, e.g. pumping stations and safety overflows
We developed a Data assimilation (DA) scheme tailor-made for system-wide soft sensing and sensor validation for urban drainage tunnels
Summary
Tunnels are increasingly integrated in urban drainage systems (UDSs). Notable examples include the pioneering Tunnel and Reservoir Plan in Chicago (USA), the Thames Tideway Tunnel in London (UK) for overflow interception and the Deep Tunnel Sewerage System in Singapore for. The depth and scale of urban drainage tunnels allow UDSs to minimize disruption at the surface level and achieve attractive cost-benefit ratios.
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