TKI Prisma 3 contributes to more sustainable operations by Port Authorities. We do so by providing innovative solutions for sediment management.
Prisma 3 builds on the work carried out in predecessor projects Prisma 1 (DEL101) and Prisma 2 (DEL126).
This work is carried out in a consortium consisting of multiple research partners: the Port of Rotterdam Authority (POR), Rijkswaterstaat (RWS), Van Oord Nederland, Boskalis Nederland and Baggermaatschappij van der Kamp.
TKI Prisma3 consists of four distinct work packages that all provide a part of the puzzle for improving sediment management.:
- Use tidal- and river dynamics for final transport of dredged sediment towards sea
- Optimize intake and disposal of sediment using a sediment transport model
- Beneficial reuse of dredged sediment on a large scale
- Data science for more efficient dredging trips
Each work package is briefly described below.
Work package 1: Use tidal- and river dynamics for final transport of dredged sediment towards sea
Work Package 1 is about the fate of released dredged fine sediments driven hydrodynamic and sediment transport processes relative to the natural dynamics of background fine sediments.
The question is at which location(s) and tidal window(s) release is most favourable to enhance dispersion towards the sea and reduce return flow to dredging locations.
Ultimately, there are three possibilities for this fate:
- Transport towards sea
- Local sedimentation in dredging areas managed by POR or RWS
- Local sedimentation outside dredging areas (e.g. side channels, dead arms, shallow or intertidal areas)
The relative contribution of each term determines the success of the release strategy (either from an ecological or economical point of view). Such strategy shouldn’t result in gradual gain or loss of sediment in the system, artificially high or low suspended sediment concentrations or enhanced dredging volumes.
A combination of monitoring and modelling is required to quantify the transport and re-sedimentation of dredged sediment more accurately than presently possible. With a transport model it is easy to determine a closed sediment balance, but such model requires a lot of field data for model calibration and validation. From field data alone we can learn a lot on system behaviour, but it is very difficult to construct a sediment balance from field data alone, as temporal and spatial variability in sediment dynamics is high. Also, it is very difficult to make a clear distinction between released dredged sediments and natural sediments. The combination of monitoring and modelling can overcome these limitations.
Fortunately, PRISMA-3 doesn’t start at zero, but builds upon a substantial number of studies on natural and dredged sediment studies and observations. During previous projects such as PRISMA 1/2, SURICATES and SALTI, substantial progress was made on monitoring of natural sediment dynamics, plume dispersion monitoring and numerical modelling of natural sediment dynamics and near- and far-field plume dispersion. From these earlier projects, results as well as uncertainties, open ends and recommendations are used to define the scope of work of PRISMA-3.
10-12 June 2024 a pilot with sediment released at a location in the high energetic part of 'het Scheur' is carried out to reduce the sailing distance significantly. The released sediment and natural sediment dynamics are monitored extensively by a combination of sailing transect plume and flow measurements with ADCP, OBS and CTD. Additionally frame measurements with ADCP, OBS and CTD have been conducted for longer term data of the background concentration and hydrodynamics. The data is being analyzed in the 2nd half of 2024.
Figure 1: Images from the sediment placement pilot and monitoring campaign
Work package 2: Optimize intake and disposal of sediment using a sediment transport model
The main research questions of this work package are: How much reduction in maintenance dredging can be obtained by pipeline transport of sediment? What are the optimal suction and release locations and geometry of such pipeline transport system? How much reduction in emissions and costs can be obtained by pipeline transport of dredged sediment compared to ordinary dredging and sailing it to sea by dredging vessels?
An analysis is made to determine the maximum pipe length over which transportation of muddy dredged sludge is still feasible. Based on energy considerations the break-even point of pipeline transport compared to regular sailing and disposal with a TSHD lies at approximately 1.5-3.5km. Next step is to carry out far-field dispersion simulations for different release distances to investigate the return flow of released sediment into the port.
Work package 3: Beneficial reuse of dredged sediment on a large scale
Over the year vast amounts of sediments are dredged in the Port of Rotterdam. Currently these constitute an important financial and engineering pressure to the port. The maintenance dredging has an order of magnitude of about 10 million m3/yr. On the other hand, climate change and sea level rise are also putting the region of Rotterdam under pressure, while the availability of these large amounts of sediment could be beneficial for economic activities in the region too, like for example agriculture and the production of filling material for infrastructure use. It would be ideal, but certainly not trivial, to accommodate a fraction of the sediment extracted from the port to fight the coastal safety threats and contribute to the regional economy and infrastructure.
Lab experiments have been carried out with marine worms to test their influence on speeding up the consolidation and ripening of fluid (dredged) mud. The tests showed promising results. Marine worms can speed up dewatering of dredged mud with months which could help the applicability of beneficial reuse of dredged sediments a lot because more sediment could be treated in a shorter period of time.
A graduation student is working on comparing different beneficial reuse of dredged sediment strategies to find the strategy with highest potential.
Work package 4: Data science for more efficient dredging trips
Often dredging is performed based on experience. POR and RWS together have a huge database of dredging trips performed over the last years.
In this work package a data science analysis of the trips in this database is performed to investigate whether trends and correlations can be observed which can be used to improve the dredging operations in terms of locations and moments to carry out dredging.
A student intern is analyzing historical dredge data and correlating it to metocean conditions like river discharge, wave conditions, tides to investigate the links between dredging efforts and driving forces for different port areas.
