Kwasi Appeaning Addo

Impacts of Coastal Inundation Due to Climate Change in a CLUSTER of Urban Coastal Communities in Ghana, West Africa

The increasing rates of sea level rise caused by global warming within the 21st century are expected to exacerbate inundation and episodic flooding tide in low-lying coastal environments. This development threatens both human development and natural habitats within such coastal communities. The impact of sea level rise will be more pronounced in developing countries where there is limited adaptation capacity. This paper presents a comprehensive assessment of the expected impacts of sea level rise in three communities in the Dansoman coastal area of Accra, Ghana. Future sea level rises were projected based on global scenarios and the Commonwealth Scientific and Industrial Research Organization General Circulation Models—CSIRO_MK2_GS GCM. These were used in the SimCLIM model based on the modified Bruun rule and the simulated results overlaid on near vertical aerial photographs taken in 2005. It emerged that the Dansoman coastline could recede by about 202 m by the year 2100 with baseline from 1970 to 1990. The potential impacts on the socioeconomic and natural systems of the Dansoman coastal area were characterized at the Panbros, Grefi and Gbegbeyise communities. The study revealed that about 84% of the local dwellers is aware of the rising sea level in the coastal area but have poor measures of adapting to the effects of flood disasters. Analysis of the likely impacts of coastal inundation revealed that about 650,000 people, 926 buildings and a total area of about 0.80 km2 of land are vulnerable to permanent inundation by the year 2100. The study has shown that there will be significant losses to both life and property by the year 2100 in the Dansoman coastal community in the event of sea level rise.

The Grand Popo beach 2013 experiment, Benin, West Africa: from short timescale processes to their integrated impact over long-term coastal evolution

ABSTRACT Almar, R., Hounkonnou, N., Anthony, E., Castelle, B., Senechal, N., Laibi, R., Mensah-Senoo, T., Degbe, G., Quenum, M., Dorel, M., Chuchla, R., Lefebvre, J-P, du Penhoat, Y., Laryea, W.S., Zodehougan, G., Sohou, Z., and Appeaning Addo, K., Kestenare, E., 2014. The Grand Popo beach 2013 experiment, Benin, West Africa: from short timescale processes to their integrated impact over long-term coastal evolution. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 651–656, ISSN 0749-0208. The first large nearshore field experiment in the Gulf of Guinea was conducted at Grand Popo Beach, Benin, in February 2013, on an open wave-dominated micro- to meso-tidal coast, located mid-way between Cotonou and Lome harbours. The overall project aims at understanding at multi-scale (from event to interannual) the causes of the dramatic erosion observed throughout the Bight of Benin, and caused by the interaction of a large littoral drift with human engineering works. Grand Popo 2013 experiment was designed to measure the processes over the short term and to test the ability of an installed video system to monitor the evolution of this stretch of coast over the longer term. The beach, characterized by a low-tide terrace and a high tide reflective part, experiences a long swell (Hs=1.6 m, Tp=16 s, oblique incidence ~15–20°). Topographic surveys showed a double beach cusp system interaction and repeated surf-zone drifter runs revealed high flash and swash rip activity driven by wave dissipation over the terrace and energetic swash dynamics at the upper reflective beach. Swash was measured over a cusp system at two locations using video poles. Wave reanalyses (ERAInterim) were used to determine the wave climate and its variability, and to quantify sediment transport. This robust methodology is thought to be replicated elsewhere in different coastal environments in West Africa, in particular with the objective to monitor various sites within the framework of the new West African Coastal Observatory.

Shoreline morphological changes and the human factor. Case study of Accra Ghana

The interface between the sea and land is a very dynamic system that is always migrating landward or seaward. The landward migration results in the shoreline threatening coastal infrastructure and destroying the coastal environment. Coastal erosion has resulted in both social and economic problems. Coastal cities have also experienced increasing infrastructure development and population growth. This has resulted in a land “squeeze situation” in which both the shoreline and the “humanline” are competing for space along the coast. This struggle for space could result in serious environmental disaster as a result of the dynamics of the oceanic system, which could impact the immediate environs severely. The aim of this study was to determine if the rate of human encroachment of coastal lands for development exceed the rate at which the shoreline is moving inland as part of its natural cyclic behaviour. This study used 1985 aerial photographs and 2005 orthophoto map of the Accra western coast. Major land cover was identified, classified and overlayed in GIS environment. This enabled changes to be estimated. The shorelines were also digitised and the rate of change computed using the DSAS software. The results indicate that the estimated total area of land lost by human encroachment on the coastal land within the period under study is about 242,139.7 m2. However, the rate of land lost to human development is about 8,349.64 m2/year, which is relatively high. The historic rate of erosion computed for the period under study is about 1.92 m/year. Comparing the two rates indicates that human activities are moving closer to the shoreline as compared to the rate at which the shoreline is moving inland. This study recommends that setback lines should be put in place to protect lands for the shoreline’s cyclic activities.

Medium resolution satellite imagery as a tool for monitoring shoreline change. Case study of the Eastern coast of Ghana

ABSTRACT Jayson-Quashigah, P-N., Appeaning Addo, K. and Kufogbe, S.K., 2013. Shoreline monitoring using medium resolution satellite imagery, a case study of the eastern coast of Ghana. Shoreline change analysis provides important information upon which most coastal zone management and intervention policies rely. Such information is however mostly scarce for large and inaccessible shorelines largely due to expensive field work. This study investigated the potential of medium resolution satellite imagery for mapping shoreline positions and for estimating historic rate of change. Both manual and semi-automatic shoreline extraction methods for multi-spectral satellite imageries were explored. Five shoreline positions were extracted for 1986, 1991, 2001, 2007 and 2011 covering a medium term of 25 years period. Rates of change statistics were calculated using the End Point Rate and Weighted Linear Regression methods. Approximately 283 transects were cast at simple right angles along the entire coast at 200m interval. Uncertainties were quantified for the shorelines ranging from ±4.1m to ±5.5m. The results show that the Keta shoreline is a highly dynamic feature with average rate of erosion estimated to be about 2m/year ±0.44m. Individual rates along some transect reach as high as 16m/year near the estuary and on the east of the Keta Sea Defence site. The study confirms earlier rates of erosion calculated for the area and also reveals the influence of the Keta Sea Defence Project on erosion along the eastern coast of Ghana. The research shows that shoreline change can be estimated using medium resolution satellite imagery.

Changing morphology of Ghana’s Accra coast

Coastal features in Ghanas Accra coast reflect both past and present processes that have been undergoing changes. These changes are influenced by a range of morphogenic factors such as geology and climatic conditions. These regimes have shaped the coastal geomorphic features through weathering processes that decompose and disintegrate the coastal rock. Sea level rise due to climate change is expected to increase coastal erosion and thus result in rapid changes in shoreline positions. Historic rate of sea level rise in Accra coast is about 2 mm/yr (Ibe & Quelennec, 1989) which is predicted to reach approximately 6 mm/yr in the next century since it conforms to the global change (Armah et al., 2005). This will result in flooding of vulnerable areas and enable waves to break closer inland. The effectiveness of the erosion process is aided considerably by the type of geology. Accra coastal zone has three types of rock in three identified geomorphic regions. They include unconsolidated and poorly consolidated rock along the western region, the Accraian series occupying the central region and the Dahomeyan series in the eastern region. The geology has thus influenced the extent to which the coastal features have changed and the type of cliff that is formed as a result of erosion within the regions. Generally, soft rock coastal features decay more rapidly than those of hard rock and tend to act as sediment sources. Human activities such as dam construction over the Densu River, engineering interventions to check the spread of erosion and sand mining has created sediment deficit which has exacerbated coastal erosion in Accra. Anthropogenic factors are estimated to account for 70-90% of coastal erosion problems in Accra.

Assessment of the Volta Delta Shoreline Change

Shorelines fronting deltas evolve in their quest to achieve equilibrium state. Such activities have encountered the increasing human development in deltaic regions and resulted in the destruction of the environment and resources. This paper discusses the shoreline evolution trends of the Volta Delta in Ghana. The shoreline was divided into four sections based on the orientation and human interventions. Data sources for the study included satellite imageries of 1986, 1991, 2001, 2004 and 2013. Trends were statistically analysed using the AMBUR software. It emerged that the 27 years period under study, the shoreline is accreting at an average rate of about 0.53 m/yr. Section one is accreting at a rate of about 0.136 m/yr; section two is accreting a rate of about 1.703 m/yr; section three is accreting at a rate of about 2.126 m/yr; while section four is eroding at a rate of about 3.703 m/yr. This observation is significant because the area has been reported by previous studies to be eroding at a rate of about 8 m/yr. Accretion of the three sections can be explained by the presence of the Keta sea defense project (KSDP) and the shoreline orientation which influences the breaking pattern of swell waves that approach the shore. The observed development of sediment build-up will influence the sediment regime along the eastern Ghana and Togo coastal areas. There is the need to develop a systematic sub-regional coastal monitoring activity to effectively manage the coastal systems in the two countries.

Managing Shoreline Change Under Increasing Sea-Level Rise in Ghana

Relative sea-level rise will affect vulnerable coastal communities globally. Quantifying this effect on the coastal environment and infrastructure provides critical information that enables coastal managers to develop sustainable mitigation and adaptation measures. Modeling applications have enabled the past, present, and future trends in shoreline morphology to be investigated in detail. Predictive numerical models depend largely on the reliability of the input data. This article reports on using the Soft Cliff and Platform Erosion (SCAPE) numerical model to simulate future shoreline evolution trend in the central Accra coast in Ghana. The model input parameters include historic shoreline recession rates, wave data, tidal data, bathymetry, beach volume, beach topography, historic relative sea-level rise rates, and the shoreline orientation. The data fed the SCAPE numerical model which simulated the emergence of soft rock shore profiles over timescale of decades to centuries, to project future positions o...Relative sea-level rise will affect vulnerable coastal communities globally. Quantifying this effect on the coastal environment and infrastructure provides critical information that enables coastal managers to develop sustainable mitigation and adaptation measures. Modeling applications have enabled the past, present, and future trends in shoreline morphology to be investigated in detail. Predictive numerical models depend largely on the reliability of the input data. This article reports on using the Soft Cliff and Platform Erosion (SCAPE) numerical model to simulate future shoreline evolution trend in the central Accra coast in Ghana. The model input parameters include historic shoreline recession rates, wave data, tidal data, bathymetry, beach volume, beach topography, historic relative sea-level rise rates, and the shoreline orientation. The data fed the SCAPE numerical model which simulated the emergence of soft rock shore profiles over timescale of decades to centuries, to project future positions of the central Accra shoreline for the next 100 years under different scenarios of climate change. Simulated future shoreline positions overlaid on a 2005 orthophoto map of Accra enabled vulnerable areas and infrastructure at risk to be identified. It emerged that a highly populated community in central Accra will be inundated by 2065, while the Rivera beach resort will be eroded from 2035. A natural fish landing site in Osu (suburb in Accra) will be lost from 2045. The study has demonstrated that considerable ecological, economic, social, and national losses should be expected within the next century. Shoreline change management options should be explored to help mitigate the expected impact of the sea-level rise.

A biophysical and socioeconomic review of the Volta Delta, Ghana

ABSTRACT Appeaning Addo, K.; Nicholls, R.J.; Codjoe, S.N.A., and Abu, M., 2018. A biophysical and socioeconomic review of the Volta delta, Ghana. Delta regions are dynamic and rich environments with diverse economic activities and are often densely populated. Deltas are being shaped by multiple drivers, including changes in sediment delivery to the coastal zone due to catchment changes, especially construction of dams on major rivers, intensified agriculture and/or aquaculture, mining, urbanisation, human-induced subsidence, climate change, and sea-level rise. These environmental challenges have significant implications for the livelihoods of delta residents. Thus, the integrated assessment of deltas is now attracting the attention of the scientific research community to analyse and understand deltas as coupled biophysical and socioeconomic systems. Most attention has been focussed on the major deltas. This review focusses on the smaller but regionally significant Volta delta, Ghana. Previous scientific studies are limited, with more focus upstream on the Volta River basin. Many contemporary problems are recognised in the Volta delta, especially erosion and flooding of the open coast fringe, such as at the town of Keta. However, these problems are treated independently, which may hinder identifying the root causes and the most effective solutions. Equally, the emergence of new problems might be anticipated and hence better managed or even avoided. This paper reviews the present delta with emphasis on biophysical processes and socioeconomic characteristics and considers in particular the current drivers and challenges. With this information, a research agenda will be established for a more systemic approach to understanding the Volta delta, including its residents and development.

Video Oberservation of Waves and Shoreline Change on the Microtidal James Town Beach in Ghana

ABSTRACT Angnuureng, D. B., Almar, R., Appeaning Addo, K., Senechal, N., Castelle, B., Laryea, S. W., Wiafe, G., 2016. Video observation of waves and shoreline change on the microtidal James town Beach in Ghana.. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1022 - 1026, Coconut Creek (Florida), ISSN 0749-0208. The morphology of sandy beaches is highly dynamic. They are influenced by the geology of the coastal area and external hydrodynamic forcing. On long timescales (years to decades), it is more efficient and convenient to monitor beach evolution through remote sensing technics rather than through direct field measurements. Erosion is a major problem along the coastline of Ghana with over 25 erosion hotspots, including James town. Here, tides, ECMWF EraInterim re-analysis wave data and images covering the beach area have been obtained for the 2013–2014 period. This paper presents preliminary results of the first efforts in processing video-derived observations of waves and shoreline change in Ghana. The pilot application shows a strong potential of the video system in providing fair quality wave data for beach management purposes where video wave characteristics are in good agreement with EraInterim global reanalysis (daily RMSE = 0.8 m and 0.7 m for Hb and Tp, respectively). Shorelines extracted from video suggest large monthly variability driven by wave seasonality while shoreline change shows a subsequent erosion/accretion cycle.

The ability of societies to adapt to twenty-first-century sea-level rise

Against the background of potentially substantial sea-level rise, one important question is to what extent are coastal societies able to adapt? This question is often answered in the negative by referring to sinking islands and submerged megacities. Although these risks are real, the picture is incomplete because it lacks consideration of adaptation. This Perspective explores societies’ abilities to adapt to twenty-first-century sea-level rise by integrating perspectives from coastal engineering, economics, finance and social sciences, and provides a comparative analysis of a set of cases that vary in terms of technological limits, economic and financial barriers to adaptation and social conflicts.This Perspective provides a comparative analysis of how well six cities and regions with different coastal and social characteristics and adaptation constraints will be able to adapt to sea-level rise, considering technological, economic, financial, and social factors.