Quantitative research on land use and land cover (LUC) in Africa usually addresses the second half of the twentieth century, by using remote sensing data. Terrestrial photographs, which are available since 1868 in Ethiopia, are seldom used in a quantitative way. This paper presents a methodology that allows to produce land use and land cover (LUC) maps on the basis of old terrestrial photographs. Therefore, land use and land cover was investigated on historical and present-day photographs, and these interpretations were warped to the horizontal plane of the map. The resulting maps allow to gain better insights into LUC changes over a period of 140 years. The results show that woody vegetation increased strongly, together with an increase in built-up area. This occurred especially at the expense of bushland. The study validates pervious findings and shows that improved land management strategies in one of the world's most degraded areas can lead to environmental rehabilitation
o o d ri s k ma n a g e me n t i n Fl a n d e r s : p a s t d ev e l o p me n t s a n d f u t u r e c h a l l e n g e s . Wa t e r R e s o u r c e s M a n a g e m e n t , 2 7 ( 1 0 ) : 3 5 8 5 -3 6 0 6 . FLOOD RISK MANAGEMENT IN FLANDERS:PAST DEVELOPMENTS AND FUTURE CHALLENGES AbstractThis paper presents the state of the art of flood risk management in Flanders, a low-lying region in the northern part of Belgium which is vulnerable to flooding. Possible flood hazard sources are not only the many rivers which pass through the Flemish inland, but also the North Sea, which is sensitive to the predicted sea level rise and which can affect large parts of the Flemish coastal area. Due to the expected increase in flood risks in the 21 st century, the Flemish government has changed its flood management strategy from a flood control approach to a risk-based approach. Instead of focusing on protection against a certain water level, the objective now is to assure protection against the consequences of a flood, while considering its probability.In the first part, attention is given to the reasoning and functioning of the risk-based approach. Recent improvements to the approach are discussed, as well as the GIS-implementation of the entire model. The functioning of the approach is subsequently demonstrated in two case studies. The second part of the paper discusses future challenges for the flood risk management in Flanders. The driving force behind these challenges is the European Directive on the assessment and management of flood risks, which entered into force in 2007. The Flemish implementation of the directive is discussed and situated in the European landscape. Finally, attention is given to the communication of flood risks to the general public, since the "availability" of flood risk management plans is among the requirements of the EU Floods Directive.
A master plan to strengthen the weak links in the coastal defence line in the Belgium is established based on coastal flooding risk calculations. This plan takes into account an average climate change scenario to be expected in the coming decades until 2050, namely an increase of surge levels of 30 cm. More long term climate change scenarios were also investigated. A worst credible extreme scenario for the 21st century change of the hydrometeorological North Sea climate was defined, with a mean sea level rise of 2 m combined with a 8% increase of extreme wind speeds. Alternative measures to manage coastal flooding risks under such climate scenario were studied to find robust measures to adapt coastal protection to climate change until 2100. The Belgian coastal zone is low-lying, highly populated and it is very vulnerable to increased coastal flooding risks by climate change. The methodology for the coastal flooding risk calculations is based on a chain of numerical models describing characteristics of storm surges with different return periods approaching the coastal defences, the failure behaviour of these defences, the hydraulics of flooding in case of failure by breaching, overflow or overtopping of the defences and finally a GIS-based damage and casualties module adopted for use within Flanders region based on available detailed GIS-data on people and assets. The rate of increase of coastal flooding risks for different climate change scenarios is quantified using a simplified version of the chain of models described above. This generalised model chain was validated by comparing with the results of the detailed model chain for the anno 2000 case. However, flooding paths via the coastal harbours as well as local risks on top of the sea dikes in the coastal towns were disregarded in the simplified model. As a consequence the results on climate change sensitivity are limited in scope to the risks associated with breaching of the sea dikes and dunes. The calculation results show a dramatic increase of the coastal flooding risks due to breaches during 21st century. For an average climate change scenario, with an increase of surge levels by 0.8 m, the risks increase by a factor 10. For the worst credible climate change scenario, with an increase of surge levels by 2.4 m, the risks increase by a factor 100. Existing coastal defences in the Belgian coastal zone are relatively low-crested compared with surge levels. This fact increases the vulnerability of this coastal zone to climate change, as was shown by the coastal flood risk calculation results. Different adaptation measures to manage these increasing risks were compared. Based on their effectiveness to reduce risks as well as estimates of costs for implementation it was concluded that efficient adaptation measures consist of heightening and/or widening the existing dunes, sea dikes and beaches. Future research will investigate which adaptation measures can be developed in the coastal harbours for maintaining safety against flooding under climate change.
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