Based on the inundation scenarios the spatial GIS analysis for Mombasa Island by 2030, 2060 and 2090, are appraised as follows.
Scenario 1: Under the RCP 2.6 by 2030
As discussed earlier, this is the most optimistic scenario where the world is seen to have successfully curbed emissions and thus mitigated global warming such that the associated sea level changes can be presumed to be lower than under the other three IPCC scenarios. Under this scenario, Mombasa Island and its infrastructure, especially the five and three star rated hotels, along with its critical port city facilities (servicing eight countries for central and eastern Africa) would fall under threat from inundation as a result of accelerated SLR.
Areas around the Changamwe Oil Refineries, Kilindini and the Likoni areas (especially around Mama Ngina Drive) would be under threat from effects of accelerated SLR. Overall exposed area under threat from inundation is 0.5 Km2.
Figure 4.8: Inundation areas for Mombasa by 2030 under the optimistic RCP 2.6
scenario.
Scenario 1: Under the RCP 2.6 by 2060
The inundation-prone areas under the optimistic scenario of RCP 2.6 by the year 2060 are shown in Figure 4.9. By this time, island area of up to 1.4 Km2 is low
lying and susceptible to ocean disturbances in the event of a severe coastal storm event, clarified at a 1 in 100 years (1-100) year return cycle of an extreme event. The areas under threat translates to 10% of the land mass. The new areas include the areas around Makadara, the Chaani residential area on the north western side of the island, portion of Old Town and the Fort Jesus tourism attraction centre which is managed by the National Museums of Kenya.
Additional areas classified as low lying (and thus threatened by the effects of extreme events) include the railway division of the coast of Kenya, which hosts part of the Kenya Ports Authority offices and bays. Under the year 2060, the areas prone to inundation increase substantially including the areas along Mama Ngina Drive where the current State House in Mombasa is situated and sections of Kizingo as well as the Mtongwe channel which serve as the only connection between the Island and the south coast.
Figure 4.9: Inundation areas for Mombasa by 2060 under RCP 2.6 scenario. Scenario 1: Under the RCP 2.6 by 2090
As indicated in Figure 4.10, under the optimistic scenario of RCP 2.6 by the year 2090, island area of up to 2.3 Km2 is low lying and is susceptible to ocean disturbances in the event of a severe coastal storm event clarified at 1-100 year return cycle. The vulnerable area is in addition to the 12.1% affected under the 2030 and 2060 scenarios. The cumulative vulnerable area across the full period under this scenario would therefore be around 23%. This translates to a quarter of the island area becoming vulnerable within the next 100 years even under the most optimistic scenario.
An important area that is fully under inundation in this scenario is the Kilindini Harbour, Kilindini Port and areas around the Changamwe Oil Refinery. This important area has been ideal for harbour infrastructure given its unique depth, the Port Authority has recently invested over US$ 50 million in new cargo handling equipment.
Figure 4.10: Inundation areas for Mombasa by 2090 under RCP 2.6 scenario.
The new Berth 19 project includes an additional 15-acre staking yard that adds an extra handling capacity of 200,000 TEUs per annum. Under the optimistic RCP 2.6 scenario, the port of Mombasa and the new Berth 19 would be under threat from inundation in the event of a coastal storm, as illustrated in Figure 4.10 under conditions of accelerating SLR.
Scenario 2: Under the RCP 8.5 by 2030
IPCC (?) deemed the RCP 8.5 scenario to be the most pessimistic scenario, where the world population is increasing and no significant effort is made to mitigate the prevailing trends greenhouse gas emissions and the related increase in atmospheric temperatures (global warming). In essence, under this scenario, the use of fossil fuels continues unabated through the next 100 years. Figure 4.11 illustrates the inundation-prone areas for Mombasa Island by 2030.
Figure 4.11: Inundation areas for Mombasa by 2030 under RCP 8.5 scenario.
The areas under threat of inundation under this scenario include the Nyali Bridge (which is the only exit to the main highway from the island) and the multi-billion new hotel enterprise known as the English Point Marina. Under this scenario, the Changamwe Oil Refinery and its facilities are under severe threat from inundation. The area of the island under threat translates to 2.3 Km2 which is equivalent to 8.2% of the island area.
The extent of infrastructure loss under this scenario would therefore be more severe compared to the optimistic scenario RCP 2.6. The areas affected include
the Changamwe area which carries the main Mombasa-Nairobi highway and the Nyali Bridge as earlier stated, which is the main Mombasa-Malindi highway from the island to the north coast. Should these two road networks be destroyed or submerged as a result of an extreme coastal event, the two hinterlands would intermittently loose their existing connection to the island.
Scenario 2: Under the RCP 8.5 by 2060
Figure 4.12: Inundation areas for Mombasa by 2060 under RCP 8.5 scenario.
The severity of inundation impacts under this scenario escalates drastically by 2060. The two main highways connecting to the mainland as well as the oil refinery and the port facilities (part of the backbone of Mombasa and Kenya’s economy at large) would be prone to inundation. The area under threat would be approximately 2.9 Km2, which translates to 20.5% thus leading to a total of 28.7% (including the
Scenario 2: Under the RCP 8.5 by 2090
This scenario produces the most severe vulnerability results as the essential infrastructure (such as important main roads, the KPA areas which are important to the Kenyan economy, as well as the three and five-star hotels and residences along the coastal regions) are now prone to inundation. The island area of up to 3.1 Km2 is low lying and is susceptible to ocean disturbances in the event of a
severe coastal storm event, clarified at 1-100 year return cycle. The land mass under threat translates to 21.9% excluding the previous areas affected. This leads to a cumulative area of almost 50% of the land mass under threat from accelerated SLR. The significance of this result is that within 100 years close to 50% of Mombasa Island would be vulnerable to inundation and yet in contrast, hardly any specific SLR awareness or mitigation/adaptation strategies are being pursued either at local or national levels.