Utilising the full potential of dredging works: ecologically enriched extraction sites

Marine extraction sites alter the morphologyof the seabed and in doing so offer uniqueopportunities to create a new environment inthese locations. A new physical lay-out meansdeeper waters and different currents andsediment characteristics, which offerconditions to develop a new ecosystem ora sanctuary for certain fish species. Thispotential has been tested in a full-scale pilotproject in an extraction site in the North Seawithin the Building with Nature researchprogramme

Sustainable development of land reclamations and shorelines full scale experiments as a driver for public - private innovations

With 80% of the world's population living in lowland urban areas by 2050, sea levels gradually rising and societal demands on the quality of living increasing, sustainable development of coastal zones becomes increasingly urgent as well as complex. Modern strategies for the design and implementation of measures for infrastructure development, coastal protection and other functions adopt the concept of Building with Nature to handle these challenges. Recently, two full scale experiments were implemented to assess the benefits of the this approach for coastal development. The Sand Motor pilot project addresses the potential concentrated nourishments on the basis of a 21 million m3 shore nourishment at the Delfland coast in the Netherlands. This unprecedented experiment aims to protect the hinterland from flooding by letting natural processes distribute sand over shoreface, beach and dunes, thus constituting a climate-robust and environmentally friendly way of coastal protection. The second experiment addresses the concept of seabed landscaping in sand extraction sites, which aims to add ecological value to the sand borrow areas after construction. Both pilots have been monitored since their completion in 2010/2011 and will be monitored extensively in the coming years

Nearshore Bathymetry derived from Video Imagery

Owing to the economic importance of seasonal fluctuations in beach width and the frequent implementation of local beach and shoreface nourishments, coastal managers and scientists increasingly demand coastal state information at smaller spatiotemporal scales. Advanced, automated video techniques provide the means to collect such high-resolution monitoring data. Successful use of video imagery for coastal monitoring requires the quantification of relevant morphological parameters from remotely sensed information. This thesis presents two complementary methods to quantify intertidal and subtidal beach bathymetry from time-averaged video observations. Application of the new methods to a nourished beach at Egmond (The Netherlands) has confirmed their utility in support of coastal management, revealing unexpected morphodynamic behaviour that would have been hard to measure with traditional survey techniques. Stefan Aarninkhof conducted his PhD. research at the Department of Civil Engineering and Geosciences of Delft University of Technology, in close collaboration with Delft Hydraulics.Civil Engineering and Geoscience

Over de grens van water en land

Intreerede, uitgesproken bij de aanvaarding van het ambt van hoogleraarKustwaterbouwkunde aan de Technische Universiteit Delft.IntreeredeCoastal Engineerin

Quantification of bar bathymetry from video observations

Since 1992, coastal morphology and hydrodynamics of the nearshore zone have been studied from video observations, within the framework of the so-called ARGUS research program. Image data are collected every day-light hour, at seven beach locations worldwide. Timeaveraged images show bright, longshore bands of intensities, clearly indicating the locations where waves preferably break. In the nearshore zone waves generally break due to depth limitation. Because of this, locally observed light intensities can be assumed to be related to local bathymetry. This relationship has already been indicated qualitatively by Lippmann and Ho/man [1989]. In this thesis, the relationship between image intensities and bathymetry is quantified. A model called MONIMORPH ('MoNitoring MORPHOlogy') has been developed, which estimates the bottom elevation Zb from observed image intensities. This is performed by relating intensity values along a cross-shore transect to a wave parameter, and modelling this wave parameter inversely. For the time being, considerations are one-dimensional and concentrate on the actual region of wave breaking. From both statistical and physical considerations it was concluded that it might be useful to relate image intensities to the roller energy density E. divided by the squared phase speed c2 . In order to obtain a quantitative match between intensity profile and E/c2 curve, the raw intensity data are scaled by means of a three parameter model (Ibase , r, SF). The background intensity parameter Ibase and the trend removal parameter r are derived from raw image intensities, while the upscaling factor SF is related to the ratio Hsig/Hmax at the seaward boundary of the computational region. The MONIMORPH wave model comprises the inverted UNillEST-TC equations, UNlBEST-TC being a cross-shore morphodynamic model developed at DELFT HYDRAULICS. Based on boundary conditions for (Hnns' h, () and 11) and a cross-shore distribution of E/c2 , it computes the corresponding bottom elevation. Estimates obtained from single images are combined by means of a data assimilation technique. From a sensitivity analysis, a favourable mechanism, damping both initial disturbances in the boundary conditions and noise in the input intensity signal, was found to exist. It makes MONIMORPH suitable to deal with relevant initial deviations of the order of 5%. The inverse model has been calibrated against data obtained from the field campaign at Duck, October 1994, yielding a scaling relation for SF. Based on this relation MONIMORPH has been tested for 27 different situations. It was concluded that for situations within the range of calibrated wave conditions (the so-called calibration window), reliable estimates of bar bathymetry are produced: deviations at the top of the bar amount 10 to 20 cm, while the mean difference across the bar is 30 to 40 cm. The bar crest is systematically predicted too far shoreward, though the differences of 10 to 20 m are small considering the mild slope of the bar. Situations not matching the wave window have to be excluded from analysis, for the time being.Hydraulic EngineeringCivil Engineering and Geoscience