shrub, irrigated farming area, and grassland, because there are no properties like that which being part of submergence area in 2011.
Road as the main transportation infrastructure is impacted by inundation. In 2011, more than 149 km of road was permanently covered by water and
predicted will inundated almost 2.2 times in spring tide 2012. Water channel as one of the natural hydrological control can’t play it function normally by this
phenomenon because some of it covered permanently by seawater. Around 66.9 km of river was permanently converted and will be inundated to ± 257.6 km by
spring tide 2012. The complete information about recent properties of submergence area in 2011 and predicted impacted inundated properties in spring
tide 2012 can be seen in Table 4.5. Table 4.5. Properties that affecting by sea level rises and spring tide
LANDUSE TYPE PERMANENTLY
COVERED IN 2011 Ha
INUNDATED BY SPRING TIDE IN
2012 Ha
Pond 22.939
70.991 Freshwater Pond
3.156 26.726
Shrub 0.000
4.046 Embankment
950.866 2246.048
Building 25.433
857.763 Estuary forest
4.382 4.382
Planting Area 6.001
12.735 Settlement
8.750 1018.501
Marsh 16.556
11.780 Grassland
0.000 195.109
Irrigated Farming Area 0.000
132.641 Moor
5.444 16.527
ROAD TYPE PERMANENTLY
COVERED IN 2011 m
INUNDATED BY SPRING TIDE IN
2012 m
Bridge 42.0950
372.875 Flying Bridge
97.2930 109.393
Collector Road 0.0000
0.000 Other Type of Road
24450.7700 4271.079
Local Road 111881.0900
301413.116 National Road
5973.6520 5370.778
Footpath 6994.8470
6398.546
4.3.4. Comparison of Projection and Maximum Flood Occurrences
Result of projection shows different broad areas of inundation with area that ever flooded in Semarang City coastal area. Flooded area, as the result of
calculation was broader than predicted inundated area. Predicted inundation area that occur in spring tide 2012 will reach the maximally 3.42 from coastline while
the result of calculated previous maximum flooding has reached 4.48 km. maximally. The differences of result can cause by some factors i.e. rain, water
load from upper area, andor extreme event like el ninola nina, which not measured in this research.
Local rain, which was poured coastal area of Semarang City, has increased the volume of water. When rain intensity was very high, water volume increase
significantly, embankment can’t mend water discharge, so that the water spill out from embankment and flooded it surrounding area. The same mechanism
also occurred when significant water load from upper area flooded Semarang City coastal area. High debit of water from upper area can’t reach Java Sea
directly because some river has converted into submergence area and can’t play it function normally. Some area of land also has lower heights than mean sea
level even if sea level height is zero. When water load from upper area reach coastal area and can’t reach Java Sea directly, the overflow of water will flooded
surrounding area of riversubmergence area that has low altitude altitude almost equal to submergence area and can flooded subsidence area that has altitude
lower than zero if those water found the way to that area through canal, drain, etc.. When La Nina occurs, the height of sea level will be different than usual
variation. Water mass in Java Sea is colder than normal condition so that the water density is increase. The impact of colder water is water level LLWL,
MSL, HHWL becomes higher and when peak tides occur, seawater can reach farther land area than the normal peak tide. The illustration of differences
between predicted inundated area in spring tide 2012 and calculated previous maximum inundated area can be seen in figure 4.9.
Figure 4.9. Comparison of projected and calculated previous maximum flooded area
4.3.5. Projection Until The End of Long Term Development Plan
As the result to be accordance with development planning, the time of projection inundated area that made has in line with development planning.
Former data shows that sea level has been increase linearly by the time and predicting will continuous increase in the future.. Based on that assumption, sea
level until the end of long term development planning RPJPRencana Pembangunan Jangka Panjang of Semarang City can be predicted. In next ten
year 2021, real sea level value will reach 79.956 cm above zero, in next fifty
2.98 4.01
4.48
2.91 3.42
4.20
