|Beneficial and nature-based sediment use - Experiences from Dutch pilots
Sittoni, Luca ; Boer, Jannes ; Star, Wouter R.L. Van Der; Heuvel, Marcel J.M. Van Den; Baptist, Martin J. ; Eekelen, Erik M.M. Van; Goot, Fokko Van Der; Nieboer, Henk E. ; Doets, Irena - \ 2019
- p. 325 - 330.
Beneficial use - Building with nature - Dredging - Sediment
The natural sediment cycle is disrupted and impacted by human interventions world-wide, such as dams in rivers, port developments in estuaries, dredging activities for the maintenance of existing ports and waterways, and pollution from industrial activities. Coasts, shores, lakes and rivers suffer from an imbalance in sediment quantity and poor sediment quality. This impacts human industrial activities (e.g. navigation, logistic and tourism), life and safety (e.g. space for living, flood safety, food security and loss of productivity). In addition, shortage of sand cause by excessive sand mining or lack of sand in the environment in many locations of the world brings a special focus on fine and soft sediment, generally considered an unsuitable resource if not a contaminated waste. In line with this world-wide demand, EcoShape - Building with Nature is executing various pilots in the Netherlands and Indonesia to improve knowledge and demonstrate practical nature-based solutions regarding management, use and reuse of (fine and soft) sediments. These pilots are bonded in the EcoShape Living Lab for Mud initiative. These pilots cover the entire range from sediment in suspension to sediment as building material, embedding ecology, operations as well as socio-economic considerations. This presentation will focus on two of these pilots located in the Netherlands: the Mud Motor and de Kleirijperij (also part of the Eems-Dollard 2050 program). The Mud Motor explored potential for beneficial use of dredge sediments to feed salt marshes, through strategic disposal and optimal use of natural processes. The Kleirijperij studies the technical and financial feasibility of turning dredge sediments into clay-soil for dike construction. During the presentations we will focus on technical results as well as governance challenges and triggers critical for the realization of sustainable beneficial sediment use projects. These pilots and this presentation tight also to the 2017 CEDA and the 2018 PIANC working groups on Beneficial Sediment Use.
Beneficial use of dredged sediment to enhance salt marsh development by applying a ‘Mud Motor’
Baptist, Martin J. ; Gerkema, T. ; Prooijen, B.C. van; Maren, D.S. van; Regteren, M. van; Schulz, K. ; Colosimo, I. ; Vroom, J. ; Kessel, T. van; Grasmeijer, B. ; Willemsen, P. ; Elschot, K. ; Groot, A.V. de; Cleveringa, J. ; Eekelen, E.M.M. van; Schuurman, F. ; Lange, H.J. de; Puijenbroek, M.E.B. van - \ 2019
Ecological Engineering 127 (2019). - ISSN 0925-8574 - p. 312 - 323.
Building with Nature - Nature-based solutions - Cohesive sediment - Dredging - Salt marshes - intertidal flats
We test an innovative approach to beneficially re-use dredged sediment to enhance salt marsh development. A Mud Motor is a dredged sediment disposal in the form of a semi-continuous source of mud in a shallow tidal channel allowing natural processes to disperse the sediment to nearby mudflats and salt marshes. We describe the various steps in the design of a Mud Motor pilot: numerical simulations with a sediment transport model to explore suitable disposal locations, a tracer experiment to measure the transport fate of disposed mud, assessment of the legal requirements, and detailing the planning and technical feasibility. An extensive monitoring and research programme was designed to measure sediment transport rates and the response of intertidal mudflats and salt marshes to an increased sediment load. Measurements include the sediment transport in the tidal channel and on the shallow mudflats, the vertical accretion of intertidal mudflats and salt marsh, and the salt marsh vegetation cover and composition. In the Mud Motor pilot a total of 470,516 m 3
of fine grained sediment (D50 of ∼10 μm) was disposed over two winter seasons, with an average of 22 sediment disposals per week of operation. Ship-based measurements revealed a periodic vertical salinity stratification that is inverted compared to a classical estuary and that is working against the asymmetric flood-dominated transport direction. Field measurements on the intertidal mudflats showed that the functioning of the Mud Motor, i.e. the successful increased mud transport toward the salt marsh, is significantly dependent on wind and wave forcing. Accretion measurements showed relatively large changes in surface elevation due to deposition and erosion of layers of
watery mud with a thickness of up to 10 cm on a time scale of days. The measurements indicate notably higher sediment dynamics during periods of Mud Motor disposal. The salt marsh demonstrated significant vertical accretion though this has not yet led to horizontal expansion because there was more hydrodynamic stress than foreseen. In carrying out the pilot we learned that the feasibility of a Mud Motor depends on an assessment of additional travel time for the dredger, the effectiveness on salt marsh growth, reduced dredging volumes in a port, and many other practical issues. Our improved understanding on the transport processes in the channel and on the mudflats and salt marsh yields design lessons and guiding principles for future applications of sediment
management in salt marsh development that include a Mud Motor approach
Response of benthic fauna to experimental bottom fishing : A global meta-analysis
Sciberras, Marija ; Hiddink, Jan Geert ; Jennings, Simon ; Szostek, Claire L. ; Hughes, Kathryn M. ; Kneafsey, Brian ; Clarke, Leo J. ; Ellis, Nick ; Rijnsdorp, Adriaan D. ; Mcconnaughey, Robert A. ; Hilborn, Ray ; Collie, Jeremy S. ; Pitcher, C.R. ; Amoroso, Ricardo O. ; Parma, Ana M. ; Suuronen, Petri ; Kaiser, Michel J. - \ 2018
Fish and Fisheries 19 (2018)4. - ISSN 1467-2960 - p. 698 - 715.
Dredging - Effects of trawling - Fishing impacts - Invertebrate communities - Systematic review - Taxonomic analysis
Bottom-contact fishing gears are globally the most widespread anthropogenic sources of direct disturbance to the seabed and associated biota. Managing these fishing disturbances requires quantification of gear impacts on biota and the rate of recovery following disturbance. We undertook a systematic review and meta-analysis of 122 experiments on the effects-of-bottom fishing to quantify the removal of benthos in the path of the fishing gear and to estimate rates of recovery following disturbance. A gear pass reduced benthic invertebrate abundance by 26% and species richness by 19%. The effect was strongly gear-specific, with gears that penetrate deeper into the sediment having a significantly larger impact than those that penetrate less. Sediment composition (% mud and presence of biogenic habitat) and the history of fishing disturbance prior to an experimental fishing event were also important predictors of depletion, with communities in areas that were not previously fished, predominantly muddy or biogenic habitats being more strongly affected by fishing. Sessile and low mobility biota with longer life-spans such as sponges, soft corals and bivalves took much longer to recover after fishing (>3 year) than mobile biota with shorter life-spans such as polychaetes and malacostracans (<1 year). This meta-analysis provides insights into the dynamics of recovery. Our estimates of depletion along with estimates of recovery rates and large-scale, high-resolution maps of fishing frequency and habitat will support more rigorous assessment of the environmental impacts of bottom-contact gears, thus supporting better informed choices in trade-offs between environmental impacts and fish production.