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Bottom Topography Observation in the Intertidal Zone Using the Camera Monitoring System 
TAERIM KIM 
School of Ocean Applied Science & Technology , Kunsan University, SAN 68, Miryong-Dong Kunsan 573-701 KOREA E-mail: 
trkim @kunsan.ac.kr 
Commission PS, WG VII/6 
KEY WORDS: Orthoimage, Monitoring, Bathymetry, Measurement, Change Detection, Oceanography 
ABSTRACT: 
The intertidal zone is characterized by periodic exposures to water level changes between high and low tides. Time series of 
waterline changes during a flood/ebb cycle can be utilized for supplementary data for measuring bottom topography. The waterlines 
extracted from consecutive images are substituted for depth contours using water level data. The distances between contours are 
quantified through a rectification image process. 
This technique is applied to the western coastal regions of Korea. This coastal area is famous for high tidal ranges over 7 meters 
and very mild slope expanding the intertidal mud flat for several kilometers. The traditional bottom topography measurement 
method is very difficult to apply in these regions because of the very mild slope and muddy environment. 
A camera monitoring technique supported by natural water level changes produces bottom topography with high precision. It is 
also less time consuming and more economical. The technique can be utilized effectively to the physical modeling for measuring 
bottom changes in three dimensional basin. 
1. INTRODUCTION 
The man-initiated coastal development is increasing 
recently and provokes rapid changes of environments in coastal 
area by losing its equilibrium maintained for a long period in 
nature. These undesirable impacts to the coastal environments 
also occur in a wide area of mud flat in the intertidal zone 
caused by large scaled reclamation projects or construction of 
embankment around ports. The mud flat region has been 
regarded as very stable condition and not experiencing high 
external forces compared to the sand beach. However, the 
issues generated by the change of mud flat environments 
demand regular and longterm monitoring of the coastal 
environment with the immediate remedies against the loss of 
the flat. Especially, the mud flat area is now revaluated as 
an important place ecologically and economically, and 
received nation wide interest for the preservation of that area, 
which has been deserted for a long time. In addition to the mud 
flat, sand beaches are also experiencing serious erosion 
problems being covered by shovels or mud and losing their 
merit as a resort. 
Intertidal zone is the region that is above the low-water 
mark and below the high-water mark, and only exposed during 
lowest tides. The mild slope of these regions makes it difficult 
to measure the bottom topography and sometimes the soft mud 
flat is dangerous place to survey. Because of these reasons, the 
traditional in-sifu measurements on the intertidal topography 
was done only at the small number of fixed points and had 
difficulties to figure out quantitatively the characteristics of 
wide region in the intertidal zone. Especially, considering a 
very little morphological changes of mud flat, new observation 
technique for the wide area of mud flat in the intertidal zone is 
needed. Also, in terms of numerical model, there is not enough 
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data for the comparison between the model results and the field 
data on the bottom changes in the intertidal zone. 
The advancement of digital imaging technique with remote 
controlling system makes it possible to use a camera for 
monitoring many kinds of natural phenomena. It has an ability 
to look spatial features and is more intuitive. In recent years, 
the camera observation including satellite remote sensing is 
begun to be used for monitoring longterm shoreline changes in 
several countries. However, in a case of west coast of Korea, 
the wide range of intertidal zone and the continuously changing 
flood lines are regarded as shortcomings for image observation 
of shoreline changes. Theses shortcomings can be converted to 
very valuable conditions for measuring the topography in the 
intertidal zone. The rising of boundary lines between water 
and land during the flood indicates depth contours from the 
lowest waters to the highest waters. By extracting the contours, 
we can construct three dimensional bottom topography in the 
intertidal zone and monitor morphological changes. 
In this research, new technique for the observation of 
bottom topography in the intertidal zone is introduced with 
some examples. 
2. METHOD 
This technique includes three important steps to configure 
three dimensional topography from time series image data. 
The first one is to extract boundary lines between water and 
land from time series image data during a flood. The second 
one is to estimate the depth of each flood lines extracted from 
images.