Wednesday, 7 May 2014

The pursuit of permeability

Dams versus semi-closed storm surge barriers, dikes versus inlets, flood prevention versus flood restoration… the last weeks I’ve been thinking about a potential title for my PhD manuscript, and what seems to a central ‘issue’ in the themes and cases that I study, is how to strike a balance. The balance between the 'extremes' of fully closed and (partly) open, the balance between full flood prevention and ‘free’ tidal and river floods in the delta.

This made me come up with the preliminary title: the pursuit of permeability. It reflects the continuous attempt of human actors in aiming to strike the ‘right’ balance: in the past with (nearly) zero permeability ("this never again" motto after the 1953 flood), towards compromising semi-closed (or semi-open?) flood management infrastructure measures (Oosterschelde), and nowadays towards ideas that deal with floods by allowing and even facilitating floods. Over time, different social, political, technological and economic conditions have asked for continuously re-adjusting the balance between open and closed (or anything in between) rivers or estuaries.

Such ‘greener’ ideas are amongst others represented in practice by de-poldering projects or dike relocations, allowing more space for flood and tidal dynamics. Agricultural areas are converted into floodplains for the sake of flood safety (lowering peak river discharge levels) and go hand in hand with efforts in the domain of (new) nature development. The Overdiepse polder and the Noordwaard polder fit well into this picture. But de-poldering is also proposed on different grounds: as a compensation measures for dredging the Scheldt river (Hedwige polder) or the expansion of the Rotterdam harbour (Rhoonse polder), or aiming to stimulate socio-economic activities in a not-so-attractive-anymore area (Perkpolder). All have in common though, that they are the result of a ‘shift’ in balance: apparently we are moving away from full flood protection to open or semi-open approaches towards floods – at least, in some areas of the Netherlands. How to strike the ‘right’ balance, is the contemporary (and long term) challenge both in technological, policy and social domains.

Especially the Noordwaard polder (which is the Dutch case in my project) is interesting and connects to both ‘pursuing’ and ‘permeability’. Firstly, the water managers and environmentalist who, for different reasons, have pursued de-poldering and flood restoration in the area. And secondly, because the restored flood regime is controlled by semi-permeable dikes: partly lowered at four locations (representing inlets of flood water once the river reaches a certain height). Some water should stay behind the dike, while other water should turn into a managed flood – hence the ‘permeable’ dike.

Let's see in a few years time what has remained of this initial, working title ;p.

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