Green–blue water in the city: quantification of impact of source control versus end-of-pipe solutions on sewer and river floods

Abstract

Urbanization and climate change trends put strong pressures on urban water systems. Temporal variations in rainfall, runoff and water availability increase, and need to be compensated for by innovative adaptation strategies. One of these is stormwater retention and infiltration in open and/or green spaces in the city (blue-green water integration). This study evaluated the efficiency of three adaptation strategies for the city of Turnhout in Belgium, namely source control as a result of blue-green water integration, retention basins located downstream of the stormwater sewers, and end-of-pipe solutions based on river flood control reservoirs. The efficiency of these options is quantified by the reduction in sewer and river flood frequencies and volumes, and sewer overflow volumes. This is done by means of long-term simulations (100-year rainfall simulations) using an integrated conceptual sewer-river model calibrated to full hydrodynamic sewer and river models. Results show that combining open, green zones in the city with stormwater retention and infiltration for only 1% of the total city runoff area would lead to a 30 to 50% reduction in sewer flood volumes for return periods in the range 10-100 years. This is due to the additional surface storage and infiltration and consequent reduction in urban runoff. However, the impact of this source control option on downstream river floods is limited. Stormwater retention downstream of the sewer system gives a strong reduction in peak discharges to the receiving river. However due to the difference in response time between the sewer and river systems, this does not lead to a strong reduction in river flood frequency. The paper shows the importance of improving the interface between urban design and water management, and between sewer and river flood management.

Model uncertainty reduction for real-time flood control by means of a flexible data assimilation approach and reduced conceptual models

“…As only a limited number of observations are available along river networks, simulation results with full hydrodynamic models are used to calibrate conceptual models (Meirlaen et al, 2001, Vanrolleghem et al, 2005. These conceptual models have been successfully applied for flood modelling, integrated catchment modelling and recently for real-time flood control (Wolfs et al, 2012, De Vleeschauwer et al, 2014, Wolfs et al, 2016, Meert et al, 2016, Vermuyten et al, 2018. A standard conceptual model consists of different reservoirs interconnected by hydraulic structures.…”

Impact of seasonal changes in vegetation on the river model prediction accuracy and real‐time flood control performance

“…Several successful applications of conceptual models such as river flood modelling and mapping, integrated catchment modelling and recently real-time flood control can be found in the literature (De Vleeschauwer et al, 2014;Meert, Pereira, & Willems, 2016;Vermuyten et al, 2018aVermuyten et al, , 2018bWolfs, Tran Quoc, & Willems, 2016;Wolfs, Van Steenbergen, & Willems, 2012). In a conceptual model, the river network is schematized by reservoirs interconnected by means of hydraulic structures.…”

Real-Time River Flood Control under Historical and Future Climatic Conditions: Flanders Case Study

“…The number of locations with water level and discharge observations is too limited to allow direct calibration of the conceptual model for these data (Meirlaen et al 2001;Vanrolleghem et al 2005). Successful applications of conceptual models include river flood analysis, integrated catchment modelling, and recently, real-time flood control (Wolfs et al 2012;De Vleeschauwer et al 2014;Wolfs et al 2016;Meert et al 2016;Vermuyten et al 2018a).…”