In the project Building with Nature in delta cities, small areas of tidal nature are created in heavily urbanized areas in Dordrecht and Rotterdam to mitigate the impact of human building activities on the tidal ecosystem and to create beneficial societal goals.
Delta cities are situated along rivers with tidal hydrodynamics. Large parts of the tidal ecosystems disappear as a result of urbanization, realisation of industry and water safety measures. Three different pilots investigated how to implement Building with Nature in such an urbanized tidal environment. The aim of the pilots is:
Wervenpark Dordrecht (Shipyard park)
Stadswerven is a new-build development where the municipality is creating a waterfront park, the Wervenpark, next to housing areas in the abandoned slipway of an old shipyard. Various solutions for gradual transitions between land and water were identified which enable the water to flow into the park when the tide rises. This leads to the return of tidal flooding, which is characteristic of this area. Moreover, it increases the attractiveness of the area. The hard embankment has been replaced by a nature-friendly shore that moves and develops with the dynamics of the Beneden-Merwede river stretch.
Mallegatpark Rotterdam (park Mallegat) and Nassauhaven Rotterdam (Nassau harbour)
Knowledge gained in the Dordrecht pilot was used to design natural, tidal bank systems along the urbanized parts of the Nieuwe Maas river in Rotterdam. The designed bank systems will contribute to the goals of the European Water Framework Directive and to the ambitions of the Municipality of Rotterdam to improve quality of life along the Nieuwe Maas river (liveability and recreation) (Gemeente Rotterdam, 2018).
Costs and benefits
The restoration of tidal ecosystems potentially leads to cost reduction, for instance by reducing the need for hard coastal defence structures, and to additional benefits including:
The pilot projects in Dordrecht and Rotterdam were initiated when the municipality of Dordrecht searched for partners to advance their aim to greenify the city and to strengthen her name as an 'innovative water city' and when Rotterdam initiated the programme ‘Rivier als Getijdepark’ (English: ‘River as a tidal park’) (Boer et al. 2014) in which EcoShape participated.
Location of pilots (topographic layer: © OpenStreetMap.org contributors).
Wervenpark Dordrecht (Shipyard park)
The Municipality of Dordrecht aimed to strengthen her name as an ‘innovative water city’, to greenify the city and the island of Dordrecht and to educate and show that the city is positioned on an island. To advance these goals, the Municipality found a partner in the Building with Nature consortium Ecoshape, which presently has as one of the main goals to show that Building with Nature in actual projects is effective.
The redevelopment site of Stadswerven Dordrecht (Shipyard Dordrecht), located between the tidal rivers Beneden-Merwede and the Wantij, was selected as the perfect area to combine the goals of Ecoshape and the Municipality of Dordrecht. Financial aid was obtained from the European Fund for Regional Development (EFRD).
Selected location for the pilot Wervenpark in Dordrecht.
Park Mallegat Rotterdam (Mallegatpark) and port of Nassau Rotterdam (Nassauhaven)
Within the program ‘Rivier als Getijdepark’ (English: ‘River as a tidal park’) (Boer et al. 2014), initiated by the Municipality of Rotterdam, with participation of Ecoshape, two pilot locations were selected. Next to the Municipality of Rotterdam and Ecoshape this program is joined by numerous partners including Rijkswaterstaat (national water authority), the Province of Zuid-Holland, several municipalities in the Rotterdam region and the Port of Rotterdam. All partners have individual ambitions to be carried out within the programme diverting from upgrading liveability to increasing ecological value or enhancing water quality.
Selected locations for the pilots Mallegatpark (left) and Nassauhaven in Rotterdam (right) (image from/adapted after De Urbanisten, 2016).
In the beginning of the exploration phase, typical elements within a river system were linked to Building with Nature-type interventions (see table) to inspire urban designers and landscape architects in the first phases of the projects. Later on, during a system analysis, the physical and ecological processes that direct the design considerations were taken into account in more detail.
Impression of the nature friendly riverbank in Nassauhaven
(image taken from Van den Berg, 2018)
In the pilot Wervenpark Dordrecht, a park is designed in which a part will have a traditional park layout while a lower lying part will develop as tidal area. In the pilot Mallegatpark a tidal channel is constructed in connection with the recently redesigned park on shore with the goal to increase the experimental and natural value of the park and its surroundings (Van den Berg, 2018). In the Nassauhaven pilot, a nature friendly riverbank is constructed in the Nassauhaven alongside the existing Nassauhaven park. At this location 18 floating houses will be constructed as well (Van den Berg, 2018). The goal of the nature friendly river bank is to increase the experimental and natural value of the park and harbour and to contribute to ecological processes.
System analysis was performed regarding physical, ecological, governmental and social aspects. For Wervenpark Dordrecht, the system analysis was done by a desk study, field trips and interviews with several stakeholders (De Jong and Van Geest, 2014). The municipality defined the locations based on nature measurements. Financial feasibility was an important criterion.
A less in-depth physical system analysis has been carried out for the tidal river ranging from the North Sea till the Island of Dordrecht (De Jong et al., 2015a) including both the pilot of Dordrecht and the pilots in Rotterdam. One of the results that proved very helpful in the communication between the consulting companies and the municipality of Rotterdam was a map and a table (see images below) which linked typical river elements with possible Building with Nature-type interventions. Though it is a strong simplification of the actual physical and ecological processes that direct the designing considerations, it facilitated the communication between the urban designers and landscape architects in the first phases of the project. It contributed to the general vision on what might potentially be feasible.
Table linking river elements (natural and man-made) with Building with Nature interventions: which interventions are feasible at which locations? (Adapted after image made by A. Balla and V. Beumer for EFRO project)
Map showing which physical properties can be found at different river elements. It distinguishes between natural elements (floodplains, inner bends, outer bends and straight banks) and man-made elements (cribs, parallel dams, floating structures, jetties, sluices, port basins, and bridges) (source: adapted after image made by A. Balla and V. Beumer for EFRO project).
Under "Read more", the boundary conditions and goals for each pilot, based on the system analysis, are listed.
Pilot Wervenpark Dordrecht
The design phase for the Dordrecht pilot was mainly carried out by urban architects, ecologists, hydro-morphologists and engineers from both the municipality of Dordrecht and consultancy firms. Several design sessions with the specialists have been organised. Their work was integrated in several meetings between the project leaders and bilateral consultation between the specialists. Also, several meetings with stakeholders were organised for the feasibility and design.
Pilots Mallegatpark and Nassauhaven Rotterdam
For the pilots in Rotterdam a different approach was used which will probably be of use for a wider audience of designers and planners. In this approach multiple design sessions were organised with not only specialists on tidal ecology and hydrology, but also planners, designers, architects, citizen spokesman, project purchaser, permit manager, etc from the Rotterdam team and representatives of the programm partners. During these design sessions innovative solutions have been invented for specific problems or desires that were put forward. On top of this, understanding and familiarisation with the Building with Nature approach and interventions was created among the urban team. Because of the participation of the Rotterdam team and the relevant specialists many of the boundary conditions could also be determined. Issues that could not be addressed or explained during the sessions were given as ‘homework’ assignments to the responsible persons. They reported back to the project-manager well before the next meeting. This way, the design manager could incorporate the findings and agreements of the last design session in an improved version of the design.
Pilot Wervenpark Dordrecht
For the pilot Wervenpark Dordrecht, a park was designed whereby a part will have a traditional (onshore) park layout while a lower lying part will develop as a tidal area. The design of the park is not finalized yet. Below, some considerations for the design are summarized and the current state of the design is explained.
Left and below: impressions of the tidal park in Dordrecht (provisional design) (source: Municipality of Dordrecht). Upper right: provisional design (Jansen, 2015).
To protect the tidal area against erosion by waves generated by passing ships it was planned to leave the existing foundation piles of the slipway in place as bank protection. However, during the excavation for the creation of the tidal area, it was found that no foundation piles were present even though they were shown on old construction drawings of the slipway. Therefore, other options for natural shore protection had to be explored during the construction phase.
Options for realising a swimming zone at the Wervenpark or in its direct surroundings were investigated. However, the flow velocity and the waves in de Merwede due to passing ships result in unacceptable safety risks. Therefore, the option for a swimming zone was cancelled.
Besides designs for the Wervenpark, also conceptual designs were made for a hybrid shoreline (combination of hard and soft materials) along the residential area where space is limited. These designs were found not feasible at the moment, but will be reconsidered at the moment that the present shoreline needs to be replaced for maintenance purposes, or in the future when new housing blocks will be realised.
Furthermore, an ‘underwater dam’ with dead tree trunks was designed to be constructed along the shoreline of the harbour next to the Wervenpark. This dam would provide living area for fauna and would break waves in front of the vegetated shoreline. However, this design is currently not feasible as the long term ambitions for the harbour are uncertain.
Design for a hybrid shoreline (up) and 'dam' constructed with dead tree trunks (currently not implemented) (source: unknown).
Current state of the design
At the moment (June, 2018), a provisional design (‘voorlopig ontwerp’) of a barrier along the sides of the Wervenpark (reinforced ground with side wall) lies with the client for approval. There is a proposal from the client to investigate in more detail the refurbishment of the ramps and the costs of this option. The park layout will only be realised after the realisation of (directly) adjacent housing blocks.
A tidal channel will be constructed in the Nieuwe Maas in connection with the recently redesigned Mallegatpark (Van den Berg, 2018). The purpose of this tidal channel is to increase the spatial quality and natural value of the park and its surroundings. In the project, an extra dam along the bank will be constructed. This break dam has higher and lower parts allowing partial flooding of the area behind the barrier. Sedimentation will take place at the lee-side providing new habitat for tidal nature.
Impression of the Mallegatpark tidal park during low tide (top) and high tide (bottom) (source: Van den Berg, 2018, image from the Municipality of Rotterdam).
Cross-section of the Mallegatpark tidal park (source: De Urbanisten, 2016, image from the Municipality of Rotterdam).
Technical drawing of the Mallegatpark tidal park (source: De Urbanisten, 2016, image from the Municipality of Rotterdam).
Alongside the existing Nassauhavenpark, a nature friendly riverbank is constructed along with the development of 18 floating houses (project “Havenloft”) in the Nassauhaven (Van den Berg, 2018). The goal of the nature friendly river bank is to increase the experimental and natural value of the park and harbour and to contribute to ecological processes.
The nature friendly river bank has a basis consisting of grey rock. In the tidal zone, the slope of this armoured surface is more gentle and a clay layer is added to/mixed with this rock basis. This gentle surface provides a good substrate for plants to grow.
Location of the Nassauhaven project (top), impression of the nature friendly river bank and floating houses (middle) and technical design of the river bank (bottom). Images (adapted) from Van den Berg, 2018 (top) and De Urbanisten, 2016 (image from the Municipality of Rotterdam) (bottom).
The construction of the Nassauhaven projected has started in January, 2018. The construction of the Wervenpark has not started yet and the construction of the project Mallegatpark started in 2016, but was put on hold in December 2017.
Pilot Wervenpark Dordrecht
The construction of the project Wervenpark Dordrecht has not started yet.
The construction of te project tidal channel Malletgat started in 2016 (Van den Berg, 2018). However, erosion risk caused problems with the request of permits in 2017. The project was put on hold in December 2017. The planning of the project is suspended, but the ambition is still there.
The project Nassauhaven is being executed since January 2018. In spring, dredging works were executed to deepen the harbour. Dredging works are necessary to construct a stable bed for the nature friendly foreshore. In April and May work on the quay started: cables and pipes were constructed and areas where future access bridges to the floating houses will be located were modified. The first houses are expected to be present in the Nassauhaven in spring 2019.
There are no detailed operation and maintenance plans yet. In general, nature will get the opportunity to develop by itself and interference will only occur if the nature is developing in an unwanted direction. Monitoring plans of the pilots focus on flora and fauna and, for the Mallegatpark, on sedimentation.
General operation and maintenance
For the development of the tidal park an operation and maintenance plan is very important. At the moment there is no detailed plan. During a workshop the maintenance aspects were discussed. This formed the start for a new vision on maintenance from a Building with Nature point of view. In this view ecological knowledge is important. Normally the maintenance aims at recovering the constructed situation. In this case however, the nature will get space and time to develop by itself. Measures will only be taken if the nature is developing in an unwanted direction, measures will be taken. In the maintenance plan, undesired conditions and potential maintenance options will be described. Maintenance will focus on the development and maintenance of the vegetation and on erosion/sedimentation. The use of ecological interesting wave breakers, for example a wooden dam, should be taken into account in the maintenance plan.
Pilots Mallegatpark and Nassauhaven:
For the Mallegatpark no maintenance plan has been set up yet. For the Nassauhaven a management and operation plan is available. After the construction of the river bank is finished the Municipality will be responsible for the management and maintenance.
The vegetation and fauna in the Wervenpark were monitored before the tidal zone was realised. The monitoring results were used for the system analysis and the design of the park. These results can also be used as a reference for the vegetation and fauna development. Further monitoring can be useful for the maintenance plan and as input for future designs of tidal parks. A monitoring plan has been written for the Wervenpark in Dordrecht (Geest et al., 2016).
Pilots Mallegatpark and Nassauhaven:
The Rotterdam team has initiated the setup of a monitoring plan whereby Ecoshape and Rijkswaterstaat were consulted. Rijkswaterstaat will also contribute financially to the monitoring because of their Water Framework Directive requirements. The monitoring plan of Mallegatpark is not final yet, but will focus on aquatic vegetation, fish species, riparian and terrestrial vegetation, insects and birds. Furthermore, the amount of sedimentation will be monitored.
In the Nassauhaven ecological monitoring will take place for approximately 5-6 years and has started in 2016 with a zero measurement. As the project goal is to increase biodiversity among different species groups, monitoring focuses on fish, macrofauna and (riparian / aquatic) vegetation. The results of the zero measurement showed a relatively large amount of young eel taking into account that this species is under pressure. Secondly, some species where found that normally live in a more brackish environment. Furthermore, the harbour is inhabited by a relatively large amount of exotic species. Finally, at some locations in the Nassauhaven some vegetation species that are characteristic for tidal environments already settled.
Under 'Read more', the main lessons learned are given. A more in-depth exploration of the lessons learned in the pilot project in Dordrecht is described in the evaluation report of Van der Meulen and Hommes (2016).