Royal Netherlands Institute for Sea Research
Phone number
+31 (0)113 577 462
Senior Scientist
  • Coastal hydrodynamics
  • Transport of suspended sediment
  • Regional sea level variability
  • Internal waves
Deployment of a lander in the Mudmotor Project (photo: Kirstin Schulz)

Dr. Theo Gerkema

Senior Scientist

New release:

introductory textbook on tides

Theo Gerkema, An introduction to tides. Cambridge University Press, 2019.

Contains the following chapters: 1. Introductory Concepts; 2. Tidal Forcing; 3. Celestial Motions; 4. Tidal Constituents and the Harmonic Method; 5. Tidal Wave Propagation; 6. Tides in Coastal Seas and Basins; 7. Internal Tides.


Transports in the coastal zone

Every tidal period, millions of cubic meters of water and tons of suspended sediment flow back and forth between tidal basins or estuaries and the adjacent sea.  But what is, in the long run, the cumulative effect of this exchange? Where does the sediment end up? Is there sufficient import of sediment in tidal basins for the intertidal flats to keep pace with sea level rise?

These questions provide a challenge because the transports are also driven by the wind, which is highly variable, not only from day to day, but also from year to year. As a result, annual mean transports are for a large part determined by wind events: tidal basins are event-driven systems.

Realistic numerical models are an indispensable tool to analyse this variability, because they capture many more places and moments than one possibly can with measurements at sea. Still, observational work is crucial to validate models and to assess how realistic they really are.

Two types of measurement are particularly useful: long-term time series of currents, sediment concentration, salinity and other quantities, collected by instruments on a lander deployed in the sea, or at a jetty. To cover more places within a tidal cycle, we use the NIOZ research vessel Navicula; this enables us to calculate the transport of water and suspended sediment in a tidal channel.

Presently, our focus is on the transports through the Kimstergat near Harlingen, as part of the STW Mudmotor project, and on transports in the Delta in Zeeland.

Transports of water and Suspended Particulate Matter (SPM) in the Vlie Inlet, from a measurement campaign with RV Navicula in 2012.

Regional sea level variability

Annual mean sea level varies in the order of a decimeter from year to year. This inter-annual variability is also in large part due to the prevailing wind climate in different years. Regional sea level variability forms a core topic at the department of Estuarine & Delta Systems. Therefore I am also part of the NIOZ Sea Level Centre of expertise.

Education & positions

I am a member of the department of Estuarine & Delta Systems (NIOZ-Yerseke) since 2016. Before I worked as senior researcher on coastal dynamics at NIOZ-Texel, after having been postdoctoral researcher at NIOZ, LEGI Grenoble (France) and Utrecht University. Until 2010, I worked for many years on internal tides, solitons, and the effects of Earth rotation.

Linked news

Tuesday 28 August 2018
Grootschalig onderzoek slib Eems-Dollard | Large-scale study water turbidity Ems-Dollard estuary
[English below] NIOZ doet mee aan grootschalig onderzoek naar werking slib in Eems-estuarium. Om beter te begrijpen hoe het slib zich in het dynamische overgangsgebied tussen rivier en zee (zoet en zout) gedraagt, start dinsdag 28 augustus 2018 een…

NIOZ publications

Linked projects

Theo Gerkema
Netherlands Organization for Scientific Research
Project duration
1 Jan 2011 - 30 Sep 2015
MUDMOTOR Sediment for salt marshes
Theo Gerkema
Project duration
1 May 2015 - 31 Dec 2018