Room for Rivers: Risk Reduction by Enhancing the Flood Conveyance Capacity of The Netherlands’ Large Rivers

Abstract

Abstract:The Netherlands has just finished implementing the Room for the Rivers program along the Rhine and Meuse Rivers in response to increasing river discharges. Recently, making more room for the river is, however, being challenged for future application because the flood defenses are assessed to be too weak and will need reinforcement anyway. To be able to decide on the most desirable policy for the remainder of the century, we require knowledge of all benefits and costs of individual interventions and strategic alternatives for flood mitigation. In this paper, we quantify some benefits of making more room for the rivers. We recognize and quantify two risk-reducing effects and provide results of analyses for the Rhine and Meuse Rivers in The Netherlands. Making room for rivers was originally advocated because it (1) reduces the consequences of flooding, as well as (2) reduces the probability of failure of the embankments. We have now quantified these effects allowing translation into risk reduction proper. Moreover, larger floodplain surface area may influence the relationship between discharge and flood level, which implies that rivers with widened floodplains are less sensitive to uncertainties about future river discharges. This does not reduce risk proper, but makes the river system more robust, as we shall argue in the discussion where we present risk reduction and robustness as complementary perspectives for assessing strategic alternatives for flood risk management.

Robust river systems: On assessing the sensitivity of embanked rivers to discharge uncertainties, exemplified for the Netherlands' main rivers

“…Finally, we want to emphasise that our current definition of robustness for rivers deviates from that of Mens (2015) in the sense that it pertains to the river alone instead of to the entire flood risk system and it is limited to the river's function of discharging water. Elsewhere (Asselman & Klijn, 2016;Klijn et al, 2018), we showed that higher river flood levels in the Rhine and Meuse Rivers translate into an increase in consequence of flooding. To our opinion, this provides a valid argumentation to at least prevent that climate change results in higher flood levels and hence to enhance the conveyance capacity of our rivers.…”

Implementation of Nature-Based Solutions for Hydro-Meteorological Risk Reduction in Small Mediterranean Catchments: The Case of Portofino Natural Regional Park, Italy

“…(3) decrease of the impacts by landslides and slope instability at the coastal sediment amount level [68]; (4) decrease of the risk of injuries among the park visitors due to slope instability of interesting hiking paths during heavy rainfalls; (5) support for the interaction between private landowners; (6) integration of the proposed NBS with regional policies for land management/planning and with the Basin Master Plan [69,70]; (7) improvement of the visibility and governance model of the Portofino Natural Regional Park, also in the perspective of becoming a National Park; and (8) improvement of the collaboration between the park authority and the stakeholders.…”

“…(6) The reduced hydraulic capacity of the rivers makes them insufficient to transport the flows safely. (7) Several areas are highly vulnerable. For example, the villages of San Fruttuoso and Paraggi, which have already suffered repeated damage from geo-hydrological events in the last century.…”

“…An effective example of large-scale NBS implementation is the Dutch "Room for the River Program", which involved 39 local projects based on nine different types of measures. This program not only achieved benefits in terms of flood risk reduction, but it also produced other benefits, including improvements in spatial quality as well as habitat and biodiversity restoration [7,8]. Another case study is the Laojiee River Project in Taiwan, where the channelized watercourse was changed into an accessible green infrastructure corridor for the public, increasing recreation activities and the value of the area [9].…”

Towards Resilient Vital Infrastructure Systems: Challenges, Opportunities, and Future Research Agenda

“…"Room for rivers" (Klijn et al, 2018) represents another form of "building with nature" suggesting to widen the embankments and create side channels, so there would be more room for rivers to enable to managing higher water levels during floods. However, in flood protection systems, to reach an optimum resilience there should be a trade-off between this approach (increasing the absorbing and adaptive capacity of the system), and robust solutions such as raising dikes.…”