Kaohsiung catchment, TW

Kaohsiung catchment Taiwan img1The Kaohsiung region is almost entirely covered by the 3,242 km2 Kaoping watershed, originated by the Kaoping river, the longest in Taiwan. The elevation ranges from the highest peak of the Central Mountain Range at 3,952 m a.s.l. to the basin outlet at 0 m a.s.l.. Ninety percent of annual precipitation (~2,800 mm) falls in the wet season (May to September) (Water Resource Agency, 2008). The lithology in the watershed comprises Paleozoic to Mesozoic black schist and green schist, Eocene to Oligocene schist and phyllite, Miocene arigillite, Pleistocene terrace deposits and alluvium, and Modern alluvium. Seventy six percent of the area is forested: needle- and broad-leaf-broad mix, broad-leaf forest, and bamboo forest account for 65%, 8%, and 3%, respectively. The remaining 24% consists of cultivated fields (11%) and built-up areas (13%).

The Kaohsiung region is located in a seismically active zone, being in the Circum-Pacific Seismic Belt, at the convergence of the Philippine Sea plate and the Eurasian Plate. Earthquakes with magnitude higher than 5 are frequent. The most recent strong episode, the so called '2010 Kaohsiung Earthquakes' occurred on March 2010, with a sequence of events of magnitude ranging from 6.4 to 6.7. The dynamic effect of earthquakes is to degrade slope stability.
Furthermore, Southern Taiwan where Kaoshiung is located, is hit on average by 3/4 Typhoons a year, and torrential rainfalls.
In August 2009, the Typhoon Morakot impacted Taiwan and caused an extraordinary amount of rainfall, setting up new records, with a peak of precipitation of about 2777 mm, and causing widespread damages mainly in southern Taiwan.

Tested LAMPRE products

1 LIM-Product icon OFF2 ELIM-Product icon OFF3 LSMM-Product icon OFF4 LStats-Product icon OFF5 3DSDM-Product icon OFF6 LRIM-Product icon OFF

Physiographic settings

Mountainous landscape with deep slopes and narrow valleys is the predominant morphological setting, but an alluvial plan (including the costal plan) along the Kaoping river is also present.

Relevant phenomena

The combined influence of typhoons and earthquakes make Taiwan and in particular the Kaoshiung area very vulnerable to slope land disasters. A large number of landslides (shallow and deep), debris flows, mudslides and sediment-related disasters occur in the area every year.

Activities

New methodologies for event landslides recognition and mapping will be tested in spot areas inside the Kaoping watershed.

Based on activities performed for the Taiwanese test site, the article "Bayesian framework for mapping and classifying shallow landslides exploiting remote sensing and topographic data" by CNR-IRPI and Kainan University in Taiwan" was published in Geomorphology. The article is accessible online here.

LAMPRE products testing

2 ELIM-Product icon OFFLAMPRE has prepared ELIMs for different test sites ranging in areas from 25 to 80 square kilometres, including two ELIMs for the Kaopin area (Taiwan), two ELIMs for the Pogliaschina area (Liguria, Italy) and an ELIM for the Giampilieri area (Sicily, Italy).

For the Pogliaschina catchment (Italy), LAMPRE has exploited a pair of VHR stereoscopic images taken by the WorldView-2 satellite shortly after a rainfall event that triggered hundreds of landslides. In the non-shadowed areas, the ELIM was prepared semi-automatically through a standard classification of the VHR images. In the shadowed areas, landslides were not visible in the images (Figure A). By stretching the Normalized Differential Vegetation Index (NDVI) the traces left by the landslides became apparent (Figure B). Exploiting stereoscopy, a 3D model was prepared to facilitate the recognition of the event landslides, allowing for their accurate mapping (Figure C).

ELIM fig.AELIM fig.BELIM fig.C

4 LStats-Product icon OFFLAMPRE has determined the statistics of landslide areas for a number of existing inventories, including a geomorphological inventory in Umbria and event inventories in Italy and Taiwan, and for a new inventory of sub-marine landslides offshore Israel.

The areal extent of individual landslides in a region follows known statistical distributions. However, determining these statistical distributions is not simple, and LAMPRE has developed new software to facilitate this task.

LStats FigA LStats FigB

Figure A portrays a portion of a typical landslide inventory map, with many small landslides, several landslides of intermediate size, and only a few large landslides.

Figure B shows a histogram of the distribution of the area of the landslides in the map. In the chart, each vertical bar portrays the number of the landslides in a category of areas, shown for convenience in logarithmic coordinates.

LStats FigCLStats FigDLStats FigE

Figure C portrays a Kernel Density Estimation (KDE) of the landslide areas. The small vertical bars along the x-axis show the number and size of the individual landslides.

Figure D portrays a more advanced analysis that shows, in log-log coordinates, the probability density function (pdf) of the landslide area. The associated uncertainty around the pdf is shaded in grey. Determining the statistical distribution of landslide areas helps to investigate the variations of landslides in time.

Figure E portrays the probability density functions of landslide areas for landslides of different ages, in the same region. The statistics of landslide size (area, volume) is a component of landslide hazard, and mandatory information for the preparation of landslide hazard models and the associated maps and scenarios.

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Contact us

Fausto Guzzetti 
Consiglio Nazionale delle Ricerche - Istituto di Ricerca per la Protezione Idrogeologica

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FACTS & FIUGRES

GA n°: 312384
Project type: Small collaborative project
Start date: 01/03/2013
Duration: 24 months
Total budget: 2,488 mln. €
EC funding: 1,964 mln. €
Total effort in person-month: 284
Other info: Visit CORDIS

 

EU FP7

The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement nº 312384. LAMPRE is managed by the Research Executive Agency (REA)

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