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| Titel |
Analysing the spatial patterns of erosion scars using point process theory at the coastal chalk cliff of Mesnil-Val, Normandy, northern France |
| VerfasserIn |
J. Rohmer, T. Dewez |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Sciences ; 15, no. 2 ; Nr. 15, no. 2 (2015-02-27), S.349-362 |
| Datensatznummer |
250119324
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| Publikation (Nr.) |
 copernicus.org/nhess-15-349-2015.pdf |
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| Zusammenfassung |
| Over the last decade, many cliff erosion studies have focused on
frequency-size statistics using inventories of sea cliff retreat sizes. By
comparison, only a few paid attention to quantifying the spatial and
temporal organisation of erosion scars over a cliff face. Yet, this spatial
organisation carries essential information about the external processes and
the environmental conditions that promote or initiate sea-cliff
instabilities. In this article, we use summary statistics of spatial point
process theory as a tool to examine the spatial and temporal pattern of a
rockfall inventory recorded with repeated terrestrial laser scanning surveys
at the chalk coastal cliff site of Mesnil-Val (Normandy, France). Results
show that: (1) the spatial density of erosion scars is specifically
conditioned alongshore by the distance to an engineered concrete groyne, with
an exponential-like decreasing trend, and vertically focused both at wave
breaker height and on strong lithological contrasts; (2) small erosion scars
(10−3 to 10−2 m3) aggregate in clusters within a radius of 5
to 10 m, which suggests some sort of attraction or focused causative
process, and disperse above this critical distance; (3) on the contrary,
larger erosion scars (10−2 to 101 m3) tend to disperse above
a radius of 1 to 5 m, possibly due to the spreading of successive failures
across the cliff face; (4) large scars significantly occur albeit moderately,
where previous large rockfalls have occurred during preceding winter;
(5) this temporal trend is not apparent for small events. In conclusion, this
study shows, with a worked example, how spatial point process summary
statistics are a tool to test and quantify the significance of
geomorphological observation organisation. |
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