Transcript Proposal for the Investigation of Sandy Beach Erosion

Proposal for the Investigation of
Sandy Beach Erosion
A Case Study on Yilan, Taiwan
by
Department of Geography
Associate Professor Hsueh-Mei Joyce Lin
Research Assistant Ming-Jen Frank Chu
Outline
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Introduction
Previous study
Purpose
Hypothesis
Study Areas
Data Manipulation
Results
Grid Analysis
Final Products – DEMs
Conclusion
Introduction
• The sediment and gravels from Taiwan’s steep mountains and
short rivers always provide a great source for supporting the
island’s sandy beach formation. In the past decades, several
coastal development projects have been completed and have
interrupted the balance of the transport. River improvement
constructions also reduce the sand and gravels coming to the
shore. These facts are causing Taiwan’s sandy beach erosion.
• Previous Study..
Previous Study
• You (1993) first claimed that several sections of Yilan
shoreline have been retreating for 0.96 meter annually from
1919 until 1987, and 7.9 meters from 1979 until 1985.
• Report from First River Management Office (2002) pointed
out that Yilan’s coast has eroded by tidal wave in the past
decade.
• Chen et al. (2004) ran an analysis based on cross section
histograms from FRMO, and discovered that majority of
Yilan’s coast is eroding.
• Hsu’s (2005) study shows that the northern arc of Yilan coast
is in its erosion process, especially in serious areas such as
Dafu and Touchen.
Summary
• Long-term study – You (1993) and Hsu (2005)’s studies show
that northern arc of Yilan coast is in erosion process; however,
southern arc is in deposition process.
• Short-term study – Chen (2005) and First River Management
Office (2005) discovered Yilan coast overall is in erosion
process.
Purpose
• Previous related researches mostly focus on the adjustment of
water line or area. Derive from the studies, this research will
emphasize on the volume change throughout the short-term
time range. Three beaches on Yilan’s coast have been selected,
the GIS-based procedures will be integrated and to generate
DTM for volume comparison and thus will support whether
these areas are in its erosion or deposition process.
Hypothesis
• The formation of the sandy beach in Yilan requires both the
sufficient sediment from Lanyang River and the energy of
longshore current.
• The construction of river improvement, conservation of water
and soil, sand/gravel mining reduce the volumes of
sedimentation of Lanyang River.
Study Area
Waiao Beach
Dingliao Beach
Wuweikung Beach
Data Manipulation
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Data Resource
Select – To select the most applicable data layer.
Edit – Topologically edit the attributes.
Krige – Interpolate the attributes into DTM.
Clip – Select the desired area for calculation.
Conversion – Convert the DTMs into TINs.
Resource
• F.R.M.O.
• 5 sub files
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Annotation
Patch
Polyline
Polygon
Point
• 69 layers
– Human structures
– Land Survey
– Landscape
• Nearly 50,000 records
Selecting
• Qualification
– Be able to show the
location
– Must have elevation
– Have to be consistent
Editing & Kriging
• Rules
– Can not overlap
– Can not be overlapped
• Kriging
Clipping
Cut the desired area
for conversion.
Converting
Results
The surface area is measured along the slope of the surface; it takes the variation in the
height of the surface into account.
The volume is the space between the surface and a reference plane set at a particular height.
Grid Analysis
• Difference
= Before – After
Difference between 2005 & 2006
Waiao Beach DEMs
Dingliao Beach DEMs
Wuweikung Beach DEMs
Next
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Q1 finished, before/after typhoon quarters, and Q4.
To calculate waterline & area change rates.
To set up Beach degradation indicators.
To gather and introduce tides, waves data.
Conclusion
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This presentation demonstrates a
method to detect onshore adjustment,
and the volume change numbers are
based on the best available data at the
time of preparation. Updates to the
DTM will be performed as new data
becomes available.
Thank you for
your participation.
Ming-Jen Frank Chu
[email protected]