Many streams in the Netherlands do not yet meet the water and ecological quality requirements set by the European Water Framework Directive (WFD), despite the application of various restoration measures. Monitoring shows that the ecological response to measures such as re-meandering, promotion of fish migration or construction of nature-friendly banks, lags behind on expectations. One of the underlying causes is the persistent problem of nutrient loading, which co-occurs with hydrological and morphological stressors (multi-stress).
A second cause is that the stream restoration projects still rely too much on the concept of manufacturability of nature and that landscape setting and system-specific natural processes are insufficiently taken into account in the design of the projects, especially the spatial and temporal scales relevant to restoration. Therefore, this research focuses on the possibilities of Building with Nature from an eco-morphological perspective in the practice of stream restoration. The research was carried out in the living lab East ‘Overijsselse Vecht’ and the living lab South ‘Raamvallei’ of the Lumbricus research program.
For the different phases in the stream restoration planning process, we investigated how the concept of Building with Nature can play a meaningful role. First, we performed a spatial analysis of the river systems (Makaske & Maas, 2015). We investigated the landscape, the ecological and historical context of the river systems, the eco-morphological characteristics of the Raam (Maas et al., 2018) and the Overijsselse Vecht (Wolfert et al., 2009; van Delft en Maas, 2018) in their current and reference situation, and we identified Building with Nature measures to develop the stream in the direction of the natural reference situation (Verdonschot et al. 2018, Dos Reis Oliviera et al. 2019).
The research revealed that the WFD stream types determined for the two river systems do not always correspond well with stream types emerging from the system analysis. A mismatch between WFD stream types and system properties is one of the reasons WFD targets are not being realized. Second, this study focused on designing with the principles of building-with-nature in stream restoration. In a design session with experts from the Vechtstromen water board, an integral sketch design of a part of the Vechtdal Junne was made, for a weir-passing secondary channel . The starting points for the design were to optimize the use of natural processes of erosion and sedimentation and vegetation succession and to tie in with the natural geomorphology of the landscape, within the preconditions of safety and the adjacent land use. During the further course of the planning process towards the final design (In Dutch: Definitief Ontwerp; DO), the Building with Nature design sketch from the design session has gradually been stripped of the Building with Nature characteristics. Wear and tear of design principles occurs regularly in planning processes.
Practical arguments from the regular design process and management weigh more heavily than innovative concepts from Building with Nature. Therefore, little to none of the measures with a decidedly experimental character that were proposed in the Building with Nature sketch design were included in the DO as they were replaced by approaches perceived as less risky. A consequence of this practice is that we cannot gain the practical experience that is necessary to find out to what extent such measures actually lead to risks. We propose that before and during the implementation of Building with Nature projects, a “quality framework” is drawn up to guarantee the realization of the objectives.
Monitoring is a must for setting up and managing the concept of Building with Nature. For many stream restoration projects, we don’t have a complete picture of to what extent the set of ecological, hydromorphological and physico-chemical goals are achieved.
An important reason for this is that most projects do not include a monitoring program, designed in such a way that specific effects of the taken measures can be captured. Oftenmeasurements are taken, but not at the right locations or at the right time to be able to determine goal realization. Additionally, in some cases, less suitable parameters and quality elements are being measured. A well designed monitoring plan could offer the possibility to keep ‘a finger on the pulse’ and possibly make adjustments to optimize the process. Such monitoring should be adaptive by design.