Christian Nolf

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

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.

Reframing China's heritage conservation discourse. Learning by testing civic engagement tools in a historic rural village

Abstract Urban heritage conservation in China has been subject to severe criticism, although there is now a sense of paradigm shift. Charters, declarations and agendas had the merit of filtering down the international discourse on heritage, while more innovative approaches were arising. The UNESCO Historic Urban Landscape recommendation, offers a new angle from which to observe this process of change. The underlying argument of this article is that HUL can provide a platform to achieve greater sustainability in transforming historic sites in China, particularly in rural areas, overcoming, at the same time, the easy shortcut of the East–West discourse of difference in respect to heritage conservation. This is primarily due to the shifting focus from the materiality of heritage to its role in sustainable development with increasing attention on the role played by local communities. By presenting the proposal for the protection of the historic rural village of Shuang Wan in the Jiangsu Province, this paper aims to reflect on this shift showing its advantages but also some of the risks. These are inherent in a discourse of heritage in danger of legitimising mere pro-growth development approaches, if not accompanied by participatory practices considerate of the specific social reality of China.

From planning to profiling: reactivating characteristic watermarks to structure the Flemish territory

Abstract Flanders distinguishes itself in Europe by its flat and dispersedly urbanized territory. If water was originally the main spatial structure, its role has been minimized over the last two centuries with the manipulation of the hydrologic network, the overlay of infrastructures, and a generalized urbanization. The development of a preventive and decentralized water policy, synonymous with making room for the water, could however, potentially reactivate the structuring capacity of water. Reporting on design investigation in the urban region of Genk, this paper demonstrates how the search of ‘space for water’ highlights and reinterprets the micro-topographic features of the landscape. Besides dealing with pressing water issues, the design of space for water can indeed simultaneously unlock the latent structure that underpins Flanderss (sub)urbanization and thereby play a key role in a requalification that redirects its development into more sustainable avenues.