2004 
  
zether 
nally, 
es all 
, with 
2000 
aures: 
6508 
), and 
78 
J trator al 
Jbare 
  
000 
imatorral 
bare 
Xaló 
duced 
5 data 
| 2000 
‘igure 
igri 
irban 
orest 
natorral 
are 
rea 2000 
rea 1978 
8 and 
forest, 
r) and 
ach of 
tween 
land 
likely 
red in 
90ha) 
ent of 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
  
e A 113% increase in urbanised areas 
On the other hand, some of the changes observed in other areas 
have a positive effect with respect to land degradation, such as: 
e A conversion or rehabilitation of 12% of the bare 
areas in 1978 to matorral (2237ha), agricultural land 
(994ha) and forests (161ha). 
e A further reforestation of former agricultural terraces 
(209ha) and matorral (258 ha). 
3.2.2  LULC changes in Lesbos 
The mapping of the various LULC classes over the island of 
Lesbos was carried out using the Landsat MSS and TM images 
of 1975 and 1999, respectively. The methodology applied 
involved a ML classification which was then tested randomly 
distributed ground truth data acquired with the use of GPS. The 
overall accuracy was 81% for the 1975 data and 89% for the 
year 1999. Figure 3a is the resulting LULC map for the year 
1975 and 3b is the same for the year 1999. Misregistration 
errors were not quantified at this stage. 
  
   
  
   
  
   
   
  
a. LULC classes, 1975 
—] saltern (23 bare 
urban Bl pine forest 
BEN olive groves L7 deciduous forest 
(3 matorral [7] maquis, sparse 5 5 
[23 maquis, dense 
  
b. LULC classes, 1999 
(— saltern EM bare © 
ES Will pine forest Y 
8 olive groves [7] deciduous forest 
(3 matorral [7] maquis, sparse 0- 5 +0 20 Kilometers 
E33] maquis, dense iL: Ll od 
Figure 3: Landuse/landcover (LULC) maps of the island of 
Lesbos with predominant LULC types produced 
from ML classification of (a) Landsat MSS data of 
1975, and (b) Landsat TM data of 1999 
The result of the ML classification for 1975 (Figure 3a), shows 
that the greatest part of the island was covered by olive groves, 
covering approximately 3096 of the entire island. Matorral and 
pine forests both covered about 2096 of the island area, 
followed by sparse (1496) and dense maquis (89^), respectively. 
Deciduous forests covered almost 5% of the total area in 1975, 
while bare and urban areas occupied a mere 1%. In the year 
1999 (Figure 1b), the olive groves were again the predominant 
landuse, occupying a slightly smaller area than they did in 
1975. Dense maquis were now the second largest LULC type 
  
555 
with 34133ha or 21% of the total area, followed by matorral 
(30576ha or 19%), sparse maquis (22530ha or 14%), pine 
forests (20168ha or 12%), bare (5213ha or 3%), oaks (1797ha 
or 1%) and urban areas (1399ha or 1%). A comparison of the 
LULC maps for 1975 and 1999 in figures 3a and 3b 
respectively, produced the graph in figure 4 below: 
  
   
  
  
  
100 60000 
| spa 
piden 
80 50000 
urb 
40000 goliv 
e» 60 > 
S d Odec 
s 30000 
© E @ forest 
2 40 
20000 pmator 
@ bare 
20 10000 
E1area 1999 
marea 1975 
  
den spa bare mator forest dec oliv — urb 
landuse in 1975 
Figure 4: Percentage of change observed between 1975 and 
1999 for eight distinct types: bare, matorral, pine 
forest, deciduous forest, olive groves, sparse maquis, 
dense maquis and urban, along with the area (ha) 
occupied by each of the types in both years 
Some of the changes that appear to have taken place between 
1975 and 1999 are directly related to degradation processes, 
namely: 
e An important decrease in forested areas, due to the 
large number of fires that took place on the island in 
the 1980s and the 1990s. 
e An increase of bare areas, from 1890ha in 1975 to 
5213ha in 1999. 
e A 4% loss of olive groves and their conversion to 
pasture due to their location in inaccessible 
mountainous areas. Over the last few decades, farmers 
in Lesbos have partly turned to tourism and tourism 
related activities while complementing their income 
from olive cultivations (Loumou et al., 2000). This is 
why only a relatively small percentage of olive groves 
were lost. 
e The increase in urban land (23%) is partly because of 
tourism, but mainly takes places in areas near the 
capital of the island (Mytilene) where the population 
is increasing. 
3.3 Runoff modelling 
The SCS Curve Number method (SCS, 1972) was utilised for 
the estimation of event runoff. The model was developed by 
studying overland flow in many small experimental catchments 
and is one of the most widely used methods to compute direct 
storm runoff (SCS, 1972; Maidment, 1993). The general form 
of the relation is ‘well established by both theory and 
observation’ (Maidment, 1993). No runoff occurs until rainfall 
(P) equals an initial abstraction I,. After allowing for I,, the 
depth of runoff Q is the residual after subtracting F, the 
infiltration of water retained in the drainage basin (excluding I,) 
from the rainfall P. The potential retention S is the value that (F 
+ I.) would reach in a very long storm. According to the model: 
Q- (P-0.2S) (1) 
P « 0.85