Coping with uncertainty in water engineering projects embracing natural dynamics


R.E. van den Hoek

A.Y. Hoekstra

M.S. Krol


University of Twente



2009 - 2013


The Dutch struggle against the forces of seas and rivers remains an important topic of special interest. In the past, Dutch engineers tamed these forces with bold projects aimed at controlling the dynamics of natural systems. Events like the dramatic flooding of the Dutch South-Western Delta in 1953 assured that ‘human safety’ remained the most important driver of water engineering projects. As a consequence, ecosystems and natural processes were regularly not taken into account and were damaged. In our current society, issues like climate change and sustainable development are receiving ever more attention. Due to this tendency, the Dutch government and dredging companies strive for a paradigm shift in water engineering: future projects should embrace natural dynamics instead of strictly controlling the system. This innovative approach, called ‘Building with Nature’ (BwN), can have multiple appearances. For instance, in the Sand Engine project, a natural material (sand) will be used by humans at the coast of Ter Heijde after which dynamic natural forces (wind, tides and currents) transport the material towards the coast to enhance the coastal defence infrastructure. Hence, the human purpose (safety) is served and the natural system gets the opportunity to develop by applying a much lower level of system control than in previous projects. Other examples of the ‘Building with Nature’ approach are using vegetation like mangrove trees in front of (tropical) coasts as a flood defence mechanism (‘bio-engineering’) and creating room for rivers to decrease flooding risks.

Before the actual implementation of a water engineering project, a policy development process takes place in which uncertainty is likely to play an important role. Uncertainty in the expected effects, or perceived uncertainty, can inhibit or retard promising initiatives. An example is the case of the 2nd Maasvlakte, where final decisions underwent enormous delays, partly due to a discourse on uncertainties in the effects on silt, nutrients and biota in the Wadden Sea. Initially it was even decided not to study these effects and uncertainties at all, causing a large part of the delay. Thus, not only the uncertainties itself but also the uncertainty management is very important for a project: they should preferably be ruled out of the equation or at least be maximally reduced to be able to live with it. Projects embracing natural dynamics are expected to bear an intrinsically high uncertainty in its effects, as they are composed of measures supporting the often only partially understood dynamics of the natural system. There is possibly even less knowledge about these dynamics than about the behaviour in a controlled equilibrium, as usually strived for previously in the water engineering discipline. Hence, uncertainty in projects embracing natural dynamics is expected to be larger than in projects aimed at high system control. This will likely have consequences for policy development in ‘Building with Nature’ projects compared to high system control projects: effective uncertainty management will be even more important than previously.

The objectives of the PhD research are (1) to identify the policy-relevant intrinsic uncertainties found in water engineering projects embracing natural dynamics and (2) to identify and understand why particular strategies are used to effectively manage policy-relevant uncertainties in water engineering projects.