Sedimentary signature of a stormsurge unit in the western Netherlands coastal dunes

1
Sedimentary signature of a storm-surge unit in
the western Netherlands coastal dunes

• Sytze van Heteren, Marcel Bakker, Albert Oost, Ad
  van der Spek, Bert van der Valk

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Deltares project Coastal Safety

• mining the Holocene coastal archive for a better
  understanding of long-term coastal safety

3
The start Bergen aan Zee

• Looking for a needle in a haystack as a result of
  a successful nourishment policy

4
The start Bergen aan Zee

• Looking for a needle in a haystack as a result of
  a successful nourishment policy

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The storm November 9, 2007
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The storm November 9, 2007
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The discovery coastal erosion exposes units

• Storm-surge units are covered by dune sand and
  are exposed by coastal erosion in the course of
  time
• Active nourishment keeps the coastline in place,
  so that new exposures are rare

8
The discovery coastal erosion exposes units

• Storm-surge units are covered by dune sand and
  are exposed by coastal erosion in the course of
  time
• Active nourishment keeps the coastline in place,
  so that new exposures are rare

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The discovery storm eroded frontal dune
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The discovery storm eroded frontal dune
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The deposit Heemskerk

• shells that are oriented convex-side up
• convoluted beds at multiple levels
• slump structures
• air-escape structures
• gravel, bricks and coal

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The deposit Heemskerk

• shells that are oriented convex-side up
• convoluted beds at multiple levels
• slump structures
• air-escape structures
• gravel, bricks and coal

13
The deposit Heemskerk

• shells that are oriented convex-side up
• convoluted beds at multiple levels
• slump structures
• air-escape structures
• gravel, bricks and coal

14
The deposit Heemskerk

• shells that are oriented convex-side up
• convoluted beds at multiple levels
• slump structures
• air-escape structures
• gravel, bricks and coal

15
The deposit spatial extent

• recognizing storm-surge units on radar images
• tracing units where they are not exposed

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The process sea water invades low areas

• water rises because of surge and runup
• no ridge with uniform height but frontal dune
  with highs and lows
• sedimentation in washovers that reach a certain
  distance landward

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The process sea water invades low areas
Gysbert Boomkamp (1741)

• water rises because of surge and runup
• no ridge with uniform height but frontal dune
  with highs and lows
• sedimentation in washovers that reach a certain
  distance landward

Jan Abrahamsz. Beerstraaten (1622-1666)
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The process sea water invades low areas

• water rises because of surge and runup
• no ridge with uniform height but frontal dune
  with highs and lows
• sedimentation in washovers that reach a certain
  distance landward

19
The elevation leveling measurements

• ca. 6.5 m above mean sea level

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The age 14C analysis of articulated shell

• 1697-1805 yr AD

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The age OSL analyses of sand

• 1777-1809 yr AD

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The age historical storm surges

• 1717
• 1775/1776

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The age historical storm surges

• 1717
• 1775/1776

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The implications better predictions

• extending the monitoring series started around
  1890
• linking wave runup to storm surge
• comparing the impact of storm surges on
  artificially high frontal dunes versus naturally
  undulating dunes

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The future integrating knowledge

• morphology
• field observations
• numerical models
• historical documents