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PREDICTION OF SHORLINE CHANGE
BY USING SATELLITE AERIAL IMAGERY
A. A. Elkoushy *, E. R. A. Tolba ?
“ Faculty of Engineering- Suez canal university- 42352 Port Said- Egypt
poston2002 @nilesat.net, chab@sedapnet.org.eg
KEY WORDS: Coast, Hazards, Photogrammetry, Aerial Images, Shoreline Change
ABSTRACT:
The shoreline change due to erosion and/or sedimentation, which are induced by the effect of wave attack and/or the effect of the
coastal structures extended into the sea, could be studied by using the aerial images. Satellite aerial imagery could play an important
role in studying the changes of the shoreline. Aerial photography
and remote sensed images can provide an overview of much wider
areas and a shorter space of time than the possible used methods of field surveying or GPS. The current study was carried out to
investigate the shoreline change due to erosion and/or sedimentation by analysing aerial images and comparing its results with that
obtained from the ordinary methods of surveying. A sufficient accuracy investigated for the shoreline change of Port Said city, which
located on the northern coast of Egypt, could be obtained by using the advanced soft-wares which covered the biases and noises
from aerial images. This study showed that the use of aerial images is a useful tool to pull all information together to understand
what happening in the shoreline and predict the future events.
1. INTRODUCTION
Many of the Egyptian coastlines are subjected to varying
degrees of erosion, high profile example is the region of Port
Said city, which is located on the northern coast of Egypt. In
order to understand what is happening around the Egyptian
coastlines, maritime councils and operating authorities require
up-to-date and accurate information about the coastal
geomorphology. They are using ordinary surveying, which are
concerning with collecting, presenting and using spatial and
geographic data in digital form. The principles of land
surveying, geomatics utilities contemporary science and
technology such as GPS, satellite remote sensing and computer-
based geographic information system (GIS) are very useful to
help us understanding the changes occurred in the shoreline.
For wider area, aerial imagery can be used for a large scale of
area in which the measurements, and the results achieved
digitally.
Coastal engineering studies by remote sensing have not widely
established. This is because of the fact that the scientists do not
use the full operational capabilities of remote sensing to coastal
and environmental studies. Here, the addressed question is that
whether aerial imagery can help us to investigate the shoreline
change with high accuracy?.
Aerial photography can provide an overview of much wider
areas in a shorter space of time than the possible used methods
of field surveying and/or GPS, but the results accuracy with
using aerial imagery must be studied carefully. This study
shows a sufficient accuracy to trace the shoreline change of the
studied area using the advanced soft-wares which covered the
biases and noises from high resolutions images, so the results
from images can be improved.
209
Imagery with the highest available spatial resolution is required
to detect changes within shorelines. Four primary sources of
high-resolution satellite imagery had been evaluated: SPOT
(SPOT Image, Corp.), IRS (Space Imagining, Inc.), SPIN2
(Aerial Images, Inc), and IKNOS (Space Imagining, Inc). The
10 meters spatial resolution of SPOT, Smeters spatial resolution
of IRS, 2 meters spatial resolution of SPIN2 and | meter spatial
resolution of IKNOS.
Finally, this study will show that aerial imagery is a useful tool
to pull all of information getting from aerial images together to
understand what happening in the shoreline and predict future
events.
2. STUDY AREA
The studied area is the shoreline of Port Said city located on the
Mediterranean on the north-eastern coast of Egypt between 31?
17" N to 31° 18’ N and 32° 10’ E to 32? 20' E. This shoreline
extends about 15 kilometres to the west of Suez Canal. It has
declined seriously over the past 20 years due to the effect of the
tidal inlets of El-Manzala lake located at EI-Gamil zone and the
existence of the western Suez Canal breakwater. The prevailing
wind and wave directions in this area are northwest yearly with
net longshore sediment transport moving from west to east.
3. IMAGES DATA
The images were taken along the shoreline of Port Said, to the
north of Egypt. The shoreline of the studied area extends 20
kilometres long with an elevation ranging from 0.5 meter to 1.5
meter. Four images, during the period 1991, 1995, 1998, and
2001 with 2 m resolution, were available and had been used.
Figure 1 shows the different four images. The scale of images
was 1:60000.