Beachrocks in togo   progress report
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  • 1. Beachrocks in Togo
    Progress report
    Guido Rutten
  • 2. Timeline
  • 3. Case: Togo
    Figure 1 Location of the project. Image courtesy: maps.com; eosnap.com; Google Earth.
  • 4. Case: Togo (2)
    Exposure of beachrocks
    Unusuallength of formation (>100km)
    Data availabilitythroughcontinuousobservation
    A uniquecombination of system boundaries
  • 5. Research proposal
    Research topics
    Beachrocks &
    shoreline movement
    Controls
    Initialgeometry
    Formation of beachrocks
    Weathering of beachrocks
    Diageneticprocesses
    Controls
    Geomorphological setting
    Destructionrates
    Impact ondynamicequilibrium
    Shoreline response
    Response to low-crestedstructures
  • 6. Research proposal (2)
    “Weathering of beachrock remains a ratheruntouched topic”
    (Gischler, 2007)
    Area of focus
  • 7. Research proposal (3)
    Formation vs. destruction
    Whystudyweathering of beachrock (and notitsformation)?
    What is the potential and reliabilityof beachrock as a paleoenvironmental indicator? (e.g. tsunamis)
    Scientific
    How long will the beachrock in Togo continue to protect the shoreline?
    (Coastal)
    Engineering
    Can we use beachrock,naturalorartificial, in anecodynamicapproachto shoreline protection?
    Can we predict the occurrenceand characteristics of beachrock in deltaïc settings?
    Oil & Gas
    What is the reservoir potentialof beachrock?
  • 8. Research proposal(4)
    Research Question:
    What is the relationship between the evolution of the shoreline profile in Togo and the exposure and characteristics of beachrock along this shoreline since 1975,
    and how can we use this knowledge to predict the impact of beachrock on the shoreline evolution in the future?
    Research questions
  • 9. Research proposal(5)
    Subquestions:
    (a) What is the provenance of beachrock along the coast of Togo and what are its characteristics in terms of geometry, cementation type/degree and discontinuities?
    (b) How has the Togo shoreline developed since the first exposure of beachrock in the 1980’s?
    (c) Is there a significant relationship between the answers to question (a) and (b)?
    (d) How does this relationship relate to existing theories concerning beachrock formation and can it be used to predict future shoreline evolution?
    Research questions
  • 10. Methodology
    Processflow
  • 11. Methodology
    Dominant parameters
  • 12. Methodology
    Dominant parameters
    integration
    over time
  • 13. Methodology
    Scaleapproach
    Microscale
    Togo CaseMesoscaleGeneric
    Macroscale
  • 14. Methodology
    Microscale (cross-shorecross-section)
    Blivi (1998)
    Amieux et al (1999)
    Blivi (1998)
  • 15. Methodology
    Mesoscale (a few hundred meters longshore)
    Microscale
    cross-sections
    Airborneimagery
    interpretation
  • 16. Methodology
    Macroscale (multiple kilometers longshore)
    diagenesis: cement alteration in time
    Introduction of time component:
    multiple exposures in time
    Gradualchange in longshoredirection
    temporal variation
  • 17. Methodology
    Macroscale (multiple kilometers longshore)
     On a macroscale, the relationshipbetweenweathering and beachrock characteristicswillbedifficult to examine.
    Other research opportunitiesinclude:
    Spatialvariation of
    (a) age,
    (b) width,
    (c) inclination;
    + rel. to regionalgeology
    2. Influence of submergedlow-crestedstructureson shoreline development
  • 18. Field Campaign
    Planning
    Field Campaign term: 02.05.2011-20.06.2011
    Upon Return:
  • 19. Field Campaign
    Activities
  • 20. Goals of the Project
    The goals of this project can be denoted as follows:
    A. Understanding processes in beachrock formation and erosion
    Understanding how the physical and geometrical characteristics of beachrock affect itserosion; Investigating how this fits in the existing theories of beachrock formation.
    B. Defining an erosion prognosis and identifying weak zones in shoreline
    Given the knowledge in goal A;
    Determining how erosion will continue in the near future;
    Identification of weak zones related to the characteristics of the beachrock in place.
    C. Defining an ecodynamic approach to shoreline protection
    For the case of Togo and similar cases; Defining a shoreline protection approach that takes into account, and benefits from the results of goal A.
    Image courtesy ggpht.com
  • 21. Workingtowards the goals
    In tropic to subtropicregions, beachrock formation is likely to occur.
    Exposed beachrocks canfixate a shoreline, reducingitscapacity to maintaincoastlineequilibrium, inducinglateralshiftingof shoreline retreat.
    Betterunderstanding of regionalgeologycan help in determining the probability of beachrock occurrence
    Intermediateobservations
  • 22. Topics of furtherattention
    Details and impact of multiple exposuresthrough time
    Diageneticmineralogicalsequence
    Bacterial and chemicalaction
    Variability of wave energy (lateral and spatial)
  • 23.
  • 24. Modelling?
    Microscale: 2D cross-shore model (Xbeach?)
    Wave impact
    Influencetop surface to MSL oncross-shore sediment transport
    Mesoscale: 3D/ depth-averaged (Delft3D?)
    Wave energy distribution withdifferentialweathering
    cf. Ranasinghe and Turner (2006): Shoreline response to submergedstructures: A review
  • 25. Field campaignfinances
    * Universiteitsfonds and KIVI NIRIA fund are not confirmed. In case of non-approval, own contribution will be raised and additional sources of funding will be sought after.
    ** The student’s continued expenses in The Netherlands (housing, university fees) are not taken into account in this overview.
  • 26. Checklist beforedeparture
    Logistics:
    Research:
    • Reservationsforlaboratory
    • 30. Regionalgeologyassessment
    • 31. Sampling procedure
  • Weatheringprocesses
    Physicalweathering
    Abrasion – dependsonproperties of movingparticles
    Crystal growth
    Thermalexpansion
    Stress release
    Hydraulicaction
    Biologicalweathering
    Antropogenic
    Chemical weathering
    Dissolution
    Hydration
    Hydrolysis
    Oxidation
    Biological
  • 32. Relevant literature
    Amieux, P. (1989), "Cathodoluminescence of carbonate-cemented Holocene beachrock from the Togo coastline (West Africa): an approach to early diagenesis," Sedimentary Geology, vol. 65, pp. 261-272.
    Blivi, A. (1998). "Quelques aspects du beach-rock dans le golfe du Bénin : le cas du Togo." Revue Cames: 43-56.
    Gischler, E. (2007). "Beachrock and intertidal precipitates." Geochemical sediments & Landscapes. In Blackwell Publishing: 365–390.
    Kindler, P. and R. Bain (1993). "Submerged upper Holocene beachrock on San Salvador Island, Bahamas: implications for recent sea-level history." GeologischeRundschau82(2): 241-247.
    Rossi, G. (1988). "The beach-rock: a natural protection against coastal erosion." Un example d'utilisationd'unedefensenaturellecontrel'erosionlittorale: le gres de plage37(1): 1-10.
    Vousdoukas, M. I., A. F. Velegrakis, et al. (2009). "Morphology and sedimentology of a microtidal beach with beachrocks: Vatera, Lesbos, NE Mediterranean." Continental Shelf Research 29(16): 1937-1947.
    Vousdoukas, M. I., A. F. Velegrakis, et al. (2007). "Beachrock occurrence, characteristics, formation mechanisms and impacts." Earth-Science Reviews 85(1-2): 23-46.