Overlay Analysis of GIS Layers to Evaluate Changes on AL Sammalyah Island
Water surfaces are designed to attract migrant birds during the winter season and to develop aquatic life on the island, while channels are used to bring high-tide sea current generated water into mangrove areas.
Table 2. Land cover statistics in the study area (1999 - 2005). Building construction
| No. |
Class name |
1999 |
2005 |
Increase |
Decrease |
% Change |
| 1 |
Roads (Length, km) |
21.6
|
26.7
|
5.1
|
- |
+23.6
|
| 2 |
Roundabouts (no.) |
2 |
8 |
6 |
- |
+300 |
| 3 |
Buildings (area, sq km) |
0.05 |
0.16 |
0.11 |
- |
+220 |
| 4 |
Break waters/ bays/ ports/ petrol stations( no.) |
3/1/2/1 |
3/3/2/1 |
2Bays |
- |
28.6 |
| 5 |
Shrubs (area, sq km ) |
1.322 |
1.322 |
- |
- |
0 |
| 6 |
Palm trees (area, sq mt) |
0.164 |
0.210 |
0.046 |
- |
28.1 |
| 7 |
Mangroves (area, sq km) |
2.256 |
3.568 |
1.312 |
- |
58.2 |
| 8 |
Barren land (area, sq km) |
9.60 |
8.16 |
- |
1.44 |
-15 |
| 9 |
Footpaths/tracks (length, m) |
33.917 |
23.08 |
- |
10837 |
-32 |
| 10 |
Water bodies (area, sq km) |
0 |
0.015 |
0.017 |
- |
+New |
| 11 |
Water Channels (length, km) |
20.4 |
23.2 |
2.8 |
- |
+13.7 |
Table 1: Land cover
classes used for the
interpretation of the data
| Visual Interpretation of the aerial
photographs of 1994 and 2005 |
| 1 |
Roads |
| 2 |
Roundabouts |
| 3 |
Footpaths / tracks |
| 4 |
Buildings |
| 5 |
Break waters/ bays/ ports/ petrol stations |
| 6 |
Palm trees |
| 7 |
Mangroves |
| 8 |
Shrubs |
| 9 |
Water bodies |
| 10 |
Water Channels |
| 11 |
Barren Land |
Database building
Al Sammalyah GIS database contain both raster and vector data, large scale
aerial photographs were scanned and converted to ArcGIS geodatabase format.
Vector data were obtained from on-screen digitization of the 1999 and 2005
datasets, and are added to the geodatabase. An integrated geodatabase of
six different dates of large scale aerial photographs, 11 vector layers
spanning 3 different dates were obtained totalizing 33 vector layers showing
the status of the land cover on the island during 1999 and 2005 dates,
and assessing the rate and nature of change occurring on the island.
Results indicate good progress in the levels of greening of the island,
especially in the increase of the salt-tolerant mangrove plantation during
the study period. A geodatabase of about 40 GIS layers is now available
to the decision makers of the island for the best management of its land
resources.
CONCLUSION
On the island large-scale reclamation started in the early 1990s and has
increased very rapidly since then. This is confirmed by the decrease in
bare land and the increase in vegetated areas especially plantations of
salt-tolerant mangroves and palm trees. Urbanization and the spread of
water bodies is testimony to the development of the island for enhancing
scientific research and developing the ecosystem.
ACKNOWLEDGEMENT
The authors are grateful to the following: (i) the Emirates Heritage Club,
DER, for the financial support to carry out this work; (ii) the Research
Affaires at the UAE University for their assistance and continuous support
to this research; and finally (iii) Mr. G. Abdul Fattah for his assistance
in digitizing vector data, preprocessing of aerial photos and in preparing
some figures for this paper.