Browsing by Author "Shaghude, Yohanna W."
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Item Assessment of shoreline changes in the western side of Zanzibar channel using satellite remote sensing(2003) Shaghude, Yohanna W.; Wanna, K. O.; Lunde, B.The present study uses a satellite remote sensing approach for assessing coastal sediment dynamics in the western side of the Zanzibar channel, Tanzania. Four Landsat images (1986, 1998, 1999 and 2000) were used for the study. Investigation of the four images revealed that the Ruvu delta north of the river mouth has been growing rapidly, especially between 1986 and 1998, with an annual northward linear growth rate of about 133m year{1 and an areal growth rate of about 1 km2 every 3 years. The study identified a palaeo-shoreline feature that is parallel to the present shoreline and located about 1.9km inland from the present shoreline. An important sediment contributor to river Ruvu is derived from the Uluguru Mountains, a tropical mountainous area located about 200km from the coastline of the Tanzania mainland. The working hypothesis is that either the observed growth of the delta occurred at a gradual rate between 1986 and 1998 or it was mainly an episodic event related to the extreme rainfall events such as the 1997/98 El Nin˜o–Southern Oscillation (ENSO) event, which was associated with extreme rainfall and widespread landslides.Item Beach Sand Supply and Transport at Kunduchi in Tanzania and Bamburi in Kenya(2012) Shaghude, Yohanna W.; Mburu, J. W.; Uku, Jacqueline; Arthurton, Russell; Nyandwi, Ntahondi; Onganda, H.; Magori, Charles; Sanga, IgnatioBeach-head erosion of sandy beach plains in eastern Africa threatens tourism-related infrastructure and the livelihoods of beach users. The nature and drivers of physical shoreline change at Kunduchi, Dar es Salaam, and Bamburi, Mombasa, are described with analyses of beach sand transport through the annual monsoon cycle and the provenance and sustainability of the beach sand supply. Time-series records of wind-vectors at Dar es Salaam and Mombasa show similar averaged patterns. Because of the contrasting alignments of these coasts, the net wind-wave driven longshore transport at Kunduchi (trending NNW) is northnorth-westwards, while at Bamburi (trending NNE) there is little net transport. At Bamburi, the beaches are recharged with reef/platform-derived calcium carbonate sand and siliciclastic sand discharged from the hinterland via tidal channels. At Kunduchi, recharge comprises mostly river-borne siliciclastic sand, but riverine sand mining threatens natural replenishment, jeopardising beach maintenance. Eroding beach plain deposits contribute siliciclastic sand at both sites.Item Bilko and African capacity development in coastal and marine remote sensing(ResearchGate, 2012) Byfield, Valborg; Bernard, Stewart; Edwards, Alasdair James; Shaghude, Yohanna W.; Dobson, Malcolm; Louw, Deon C.; Oben, Benedicta M.; Robinson, Ian S.; Whittle, ChristoIn much of Africa barriers still exist to the effective use of Earth observation in marine and coastal research and management. To remedy this, the development of data access and processing capacity must go hand in hand with hands-on training in the use of satellite data. The Bilko project has been providing training resources suitable for this for 25 years. In recent years marine scientists from Africa and Europe have been using Bilko to develop lessons based on African examples taken from image data disseminated via GEONETCast in two EC funded projects. The work is part of current efforts to develop MSc level and professional training courses for use in Africa, and shows how the contribution of African experts in the development of new lessons contributes to making these more relevant.Item Biogenic Assemblage and Hydrodynamic Settings of the Tidally Dominated Reef Platform Sediments of the Zanzibar Channel(2002) Shaghude, Yohanna W.; Wannas, Kjell O.The biogenic assemblage and hydrodynamic settings of the tidally dominated reef platform sediments (TDRPS) east of the Zanzibar channel were investigated in order to characterise the carbonate sediments. Benthic foraminifera were found to be the most important group, both in terms of average abundance (> 60 % by weight) and also in terms of spatial distribution, with common occurrence in all sediments samples. Pelecypods, with an average abundance of 8 % were slightly less widely distributed. The remaining groups occurred at lower average abundance and less frequently in the sediments. Current measurements indicated that the maximum current speed is higher during spring than during neap tides. The direction is phase-dependent with flood tidal current flowing from the northern and southern tips of the island towards Zanzibar town. The ebb current flows in the opposite direction. The geomorphological setting of the carbonate platforms together with the present investigation of the currents and biogenic assemblage of the clastic sediments permits us to subdivide the reef platform area in the Zanzibar Channel into two sub-provinces: the northern and the southern. The northern sub-province contains significantly higher proportion of lithogenic particles, pelecypods, gastropod and ostracods than the southern sub-province. Some samples from the southern subprovince had significantly higher proportion of corals, than those from northern sub-province.Item Downstream and Coastal Impacts of Damming and Water Abstraction in Africa(Springer Science, 2007) Snoussi, Maria; Kitheka, Johnson; Shaghude, Yohanna W.; Kane, Alioune; Arthurton, Russell; Tissier, Martin; Virji, HassanAbstract Anthropogenic factors associated with damming and water abstraction, and the resultant environmental pressures, are reviewed in six African river catchments using records and forecasts of climatic, demographic, and land-use change. Changes in the states of the flow regime through catchment drainage systems to the coastal sea are considered in conjunction with climate change and other humaninduced pressures. The impacts of these changes on downstream and coastal environments and their communities are described in past, present, and future perspectives. Linkages between the issues and the pressures of damming and water abstraction are appraised and scientific, policy, and management responses proposed aimed at remedying existing and perceived future negative impacts. The study proposes that there is a need to integrate catchment and coastal management to account for the whole water flow regime together with its human dimensions. Management priorities relating to the operation of existing damming and abstraction schemes and planning of future schemes include the following: consideration of ways in which water discharges could be adjusted to provide improvements in downstream and coastal environmental and socioeconomic conditions; addressing the problem of sediment trapping impacting on the sustainability of dam reservoirs; and assessment of downstream and coastal impacts of future schemes in the light of climate change forecasts.Item Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs, Zanzibar, Tanzania(Elsevier, 2010) Muzuka, Alfred; Dubi, Alfonse M.; Muhando, Christopher A.; Shaghude, Yohanna W.Coral reefs which are an important resource to coastal communities and nation at large are adversely affected by rate of sediment flux to the reefs. However, there is little information on seasonal trend in sediment flux and its impact at the reefs off Zanzibar. Two years’ monthly data on sedimentation at Chumbe and Bawe reefs were used to assess seasonal variability in sediment flux and its implication on the coral status. Sediment flux to the Bawe reefs for the duration of the study ranged from 0.2 to 41.5 mg cm 2 d 1, while it ranged from 0.8 to 65.8 mg cm 2 d 1 at the Chumbe reefs. Sediment fluxes at Bawe reefs were highest between November and March, while they were highest between April and September at Chumbe reefs. Generally, sediment fluxes at Bawe reefs were low compared to those at Chumbe. The total sediment input to the reefs ranged from 4615 to 123,403 kg d 1 for Bawe reefs and 2750 to 79,636 kg d 1 for Chumbe reefs. High sediment fluxes at Bawe reefs between November and March; and the Chumbe reefs between April and September can be attributed to water currents and wind pattern in the east African region which are under the influence of the monsoons. The observed trend suggests that the period for coral transplant as a management option for the two sites should be different. Coral transplant can be undertaken in such a way that stress of the corals due to sedimentation can be felt after they have overcome stress from transplant process and temperature. The results from this study contribute to the much needed information for coral transplant, restoration, and managementItem Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs, Zanzibar, Tanzania(Elsevier, 2010) Muzuka, Alfred; Dubi, Alfonse M.; Muhando, Christopher A.; Shaghude, Yohanna W.Coral reefs which are an important resource to coastal communities and nation at large are adversely affected by rate of sediment flux to the reefs. However, there is little information on seasonal trend in sediment flux and its impact at the reefs off Zanzibar. Two years’ monthly data on sedimentation at Chumbe and Bawe reefs were used to assess seasonal variability in sediment flux and its implication on the coral status. Sediment flux to the Bawe reefs for the duration of the study ranged from 0.2 to 41.5 mg cm 2 d 1, while it ranged from 0.8 to 65.8 mg cm 2 d 1 at the Chumbe reefs. Sediment fluxes at Bawe reefs were highest between November and March, while they were highest between April and September at Chumbe reefs. Generally, sediment fluxes at Bawe reefs were low compared to those at Chumbe. The total sediment input to the reefs ranged from 4615 to 123,403 kg d 1 for Bawe reefs and 2750 to 79,636 kg d 1 for Chumbe reefs. High sediment fluxes at Bawe reefs between November and March; and the Chumbe reefs between April and September can be attributed to water currents and wind pattern in the east African region which are under the influence of the monsoons. The observed trend suggests that the period for coral transplant as a management option for the two sites should be different. Coral transplant can be undertaken in such a way that stress of the corals due to sedimentation can be felt after they have overcome stress from transplant process and temperature. The results from this study contribute to the much needed information for coral transplant, restoration, and managementItem Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs, Zanzibar, Tanzania(Elsevier, 2010) Muzuka, Alfred N. N.; Dubi, Alfonse M.; Muhando, Christopher A.; Shaghude, Yohanna W.Coral reefs which are an important resource to coastal communities and nation at large are adversely affected by rate of sediment flux to the reefs. However, there is little information on seasonal trend in sediment flux and its impact at the reefs off Zanzibar. Two years’ monthly data on sedimentation at Chumbe and Bawe reefs were used to assess seasonal variability in sediment flux and its implication on the coral status. Sediment flux to the Bawe reefs for the duration of the study ranged from 0.2 to 41.5 mg cm 2 d 1, while it ranged from 0.8 to 65.8 mg cm 2 d 1 at the Chumbe reefs. Sediment fluxes at Bawe reefs were highest between November and March, while they were highest between April and September at Chumbe reefs. Generally, sediment fluxes at Bawe reefs were low compared to those at Chumbe. The total sediment input to the reefs ranged from 4615 to 123,403 kg d 1 for Bawe reefs and 2750 to 79,636 kg d 1 for Chumbe reefs. High sediment fluxes at Bawe reefs between November and March; and the Chumbe reefs between April and September can be attributed to water currents and wind pattern in the east African region which are under the influence of the monsoons. The observed trend suggests that the period for coral transplant as a management option for the two sites should be different. Coral transplant can be undertaken in such a way that stress of the corals due to sedimentation can be felt after they have overcome stress from transplant process and temperature. The results from this study contribute to the much needed information for coral transplant, restoration, and management.Item Investigating the Effect of Winds and Storms on Shoreline Erosion along the Coast of Tanzania(David publishing, 2013) Mahongo, Shigalla B.; Shaghude, Yohanna W.Abstract: Wind data spanning 28 years (1977-2004) from four meteorological stations (Tanga, Zanzibar, Dar es Salaam and Mtwara) were analyzed to elucidate the effect of winds on coastal erosion along the coast of Tanzania. The investigation entailed wavelet analysis of the time series of winds which were related with past erosion events at each site. The study also analyzed qualitatively the incidences of tropical storms in relation to coastal erosion events along the coast. The results revealed that most of the critical erosion incidents in the past few decades were associated with periods of occurrence of extreme wind speeds and tropical storms. Furthermore, the results indicated that the wind speeds and the frequency and intensity of tropical storms had generally been increasing during the past three decades. The findings were consistent to those recently reported for the coast of Dar es Salaam. The increasing trends of winds and storms are considered to have direct impact on the wave climate with increased risk of shoreline wave-induced erosion that is already affecting relatively many parts of TanzaniaItem Mineralogical and Biogenic Composition of the Zanzibar Channel Sediments, Tanzania(Estuarine, Coastal and Shelf Science, 2000) Shaghude, Yohanna W.; Wannas, K. O.Sediments from the Zanzibar Channel have been analysed for mineralogical and biogenic composition. The main objective of the study was to describe the depositional environment of the sediments based on these parameters. The study was also conducted to give an insight into sediment provenance of the sediments. Quartz, feldspar (both microcline and plagioclase) and hornblende are the main mineralogical components, while zircon, muscovite, biotite and augite occur as accessory minerals. The quartz grains are generally angular to sub-angular and highly strained, indicative of immature sediments, probably derived from highly metamorphosed rocks. The presence of hornblende also supports the conclusion that the sediments are immature. A possible source is the metamorphic rocks of the Mozambique belt, located about 25–50 km from the coastline. Benthic foraminifera are the dominant biogenic constituents. Other common biogenic constituents are molluscs (pelecypods and gastropods) and corals. Bryozoans and ostracods are relatively less common, while sea urchins are accessory biogenic components. The composition and abundance of these biogenic components and morphological, sedimentological and mineralogical data permit construction of a simple model which distinguishes between three bio-physiographic settings in the Zanzibar Channel using depth contours: (1) the coastal zone (0–10 m depth); (2) the reef platform/patch reefs zone (10–20 m depth) and (3) the central channel zone (>20 cm depth). In the coastal zone, the sediments are dominated by fine sand, sized with a very prominent fine sand mode. The proportion of benthic foraminifera is lower than in the other two zones (<45%) as is the biogenic:quartz ratio (<2), but the lithogenic concentration is highest (>25%). Two lithogenic mineral components (quartz and feldspar) occur in significant proportions. In the reef platform/patch reefs zone, the sediments are coarse to medium sand sized with no distinct mode. the proportion of benthic foraminifera is highest (80–85%) there, and so is the biogenic:quartz ratio (>10) but that of lithogenic components is lowest (<5%). In the central channel zone, the sediments are medium to fine sand sized and often bimodal, with a prominent fine mode and a less prominent coarse mode. The proportion of benthic foraminifera (70–75%) is also higher than in the coastal zone but slightly lower than in the reef zone. The proportion of lithogenic components (5–20%) is higher than in the reef zone but lower than in the coastal zone and the biogenic:quartz ratios is intermediate.Item Modelling the dynamics of the Tanzanian coastal waters(Tanzania Fisheries Research Institute, 2013) Mahongo, Shigalla B.; Shaghude, Yohanna W.A numerical modeling study was carried out using the Regional Ocean Modeling System (ROMS) for the Tanzanian coast to investigate the seasonal dynamics of water circulation, temperature and salinity. The model results indicated the presence of an eddy on the surface that had been developed during the Northeast (NE) monsoon and which has not been documented previously. The study also revealed that, the core of the East African Coastal Current (EACC) passes adjacent to the coast, just off the three major islands of Pemba, Zanzibar, and Mafia. There are localized patches of strong currents parallel and adjacent to the mainland coast, with magnitudes that are influenced by the coastline configuration, bottom topography and the extent of exposure to the main stream of the EACC. The current speeds along the coast of Tanzania are lowest in February and March, and highest in July, August, and November but generally not exceeding 1 ms-1. Surface salinities generally vary between 34.8 and 35.5, whereas surface temperatures range from a minimum of 25.0°C to a maximum of 30.2°C. The modelled salinity and temperature profiles are similar to those observed from field observations of previous investigationsItem Morphodynamics of the Manyema Tidal Delta at Kunduchi, Tanzania(WIOMSA, 2013) Nyandwi, Ntahondi; Shaghude, Yohanna W.; Mburu, J. W.; Dubi, Alfonse M.; Sanga, I.; Arthurton, RussellThe prevailing northward longshore drift of beach sand on the northern part of Msasani Bay, north of Dar es Salaam, is interrupted at Kunduchi by the tidal flushing of Manyema Creek, a mangrove ecosystem partially developed for salt production. Shoreline changes around the creek mouth in recent decades have eroded coastal land and destroyed buildings, prompting stakeholders to construct protective groynes and revetments. Sand is transported across the delta by the interaction of two forcing processes – currents that flush the creek in response to tidal variation and, more generally, those generated by monsoonal wind-driven waves. A study of the sand morphology of the creek and delta platform together with time-series satellite imagery permitted demarcation of the respective sand transport pathways and morphodynamic changes in the delta over the last decade. The sand transport regime has promoted erosion of the shore to the south of the creek mouth, and has resulted in intermittent delivery of sand to beaches north of the channel. Attempts to stabilise the shore around the creek mouth are described and their effectiveness evaluated.Item On the dynamics of the Zanzibar Channel(Journal of Geophysical Research: Oceans, 2015-07-24) Zavala-Garay, J; Theiss, J; Moulton, M; Walsh, C; van Woesik, R; Mayorga-Adame, C.G; Garc ıa-Reyes, M; Mukaka, D.S; Whilden, K; Shaghude, Yohanna W.The Zanzibar Channel lies between the mainland of Tanzania and Zanzibar Island in the tropical western Indian Ocean, is about 100 km long, 40 km wide, and 40 m deep, and is essential to local socioeconomic activities. This paper presents a model of the seasonal and tidal dynamics of the Zanzibar Channel based on the Regional Ocean Modeling System (ROMS) and a comparison of the model and observations. The seasonal dynamics of the channel is forced by remote processes and the local wind. Remote forcing creates the East African Coastal Current, a portion of which flows through the channel northward with a seasonally varying magnitude. The local wind enhances this seasonality in the surface Ekman layer, resulting in a stronger northward flow during the southwest monsoon season and a weak northward or occasionally southward flow during the northeast monsoon season. The tidal flows converge and diverge in the center of the channel and reduce the transport in the channel. The remotely forced, wind-forced, and tidal dynamics contain 5%, 3%, and 92% of the total kinetic energy, respectively. Despite their low kinetic energy, the remotely forced and wind-forced flows are most relevant in advecting channel water to the open ocean, which occurs in 19 days at the peak of the southwest monsoon season. The channel is well mixed, except during brief periods in the two rainy seasons, and temporarily cools between December and February. The dispersion of passive tracers is presented as an example of potential model applications.Item Preliminary investigation on the Pleistocene/Holocene Sea-Level Changes along the Coastline of Tanzania, with reference to Unguja and Pemba Islands(2007) Muzuka, Alfred N. N.; Nyandwi, Ntahondi; Shaghude, Yohanna W.Along the coast of Tanzania, coral reefs, marine terraces and beach ridges are among the most important geomorphological features indicative of the Pleistocene/Holocene sea level changes. Three major terrace units can easily be identified on the mainland coast, namely, Mtoni (youngest), Tanga and Sakura (oldest). Three terrace units have also been identified on the Islands of Unguja and Pemba. On the basis of the difference in the terrace elevations between the two terrace systems it is postulated that the marine terraces on the islands probably represent minor fluctuations of sea level, rather than major phases of sea level fluctuation. A sand beach on the seaward side and several sand ridges on the landward side represent the Recent phase. The oldest Palaeoshoreline is approximately 5 m above the present sea level, and extends landward to more than 1 km. Specific localities around the two islands where Pleistocene/Holocene sea level changes has been preserved in the form of marine terraces and/or beach ridges include Chwaka, Uroa, Jambiani, Paje and Nungwi (Unguja island) and Vumawimbi and Kiuyu (Pemba island).Item Preliminary investigation on the Pleistocene/Holocene Sea-Level Changes along the Coastline of Tanzania, with reference to Unguja and Pemba Islands(2003) Muzuka, Alfred N. N.; Nyandwi, Ntahondi; Shaghude, Yohanna W.Along the coast of Tanzania, coral reefs, marine terraces and beach ridges are among the most important geomorphological features indicative of the Pleistocene/Holocene sea level changes. Three major terrace units can easily be identified on the mainland coast, namely, Mtoni (youngest), Tanga and Sakura (oldest). Three terrace units have also been identified on the Islands of Unguja and Pemba. On the basis of the difference in the terrace elevations between the two terrace systems it is postulated that the marine terraces on the islands probably represent minor fluctuations of sea level, rather than major phases of sea level fluctuation. A sand beach on the seaward side and several sand ridges on the landward side represent the Recent phase. The oldest Palaeoshoreline is approximately 5 m above the present sea level, and extends landward to more than 1 km. Specific localities around the two islands where Pleistocene/Holocene sea level changes has been preserved in the form of marine terraces and/or beach ridges include Chwaka, Uroa, Jambiani, Paje and Nungwi (Unguja island) and Vumawimbi and Kiuyu (Pemba island).Item Review of Water Resource Exploitation and Landuse Pressure in the Pangani River Basin(WIOMSA, 2007) Shaghude, Yohanna W.The Pangani River Basin, with a total area of 43,000 km2 is one of the most important of Tanzania’s river basins. Water and arable land are the most important resources. The water balance in the Basin is estimated at about 900 million m3 per annum. The increasing water demands to meet various socio-economic needs are placing the basin under critical water stress. Irrigation abstraction and evaporative losses at the Nyumba ya Mungu reservoir are the major contributor to the observed water stress in the basin. Deforestation on the highlands and the use of traditional and environmentally unfriendly agricultural practices also have direct impacts on the water retention capability and may significantly contribute to the observed water stress in the basin. In addition, changes in climate regime, due to increasing temperature and reduced rainfall conditions, contribute to the reduced water supply. This coupled with the land degradation problems, has multiple effects on the coastal environments. Management options, using the limited water and land resources more innovatively and sustainably, have been suggested. These options include: 1- reforming the current water rights allocation system, 2- looking for longterm strategies for improving irrigation efficiency, 3- further promotion of innovative agricultural methods and 4- application of modern innovative techniques of water storage such as Aquifer Storage and Recovery (ASR) in preference to surface water storage systems.Item Sediment Characteristics and Hydrodynamic Setting of Reef Platform Sediments of Kunduchi, North Of Dar es Salaam Harbour(2006) Shaghude, Yohanna W.; Nyandwi, Ntahondi; Muzuka, A. N. N.; Dubi, Alfonse M.; Mwaipopo, O. U.Sediment grain size distribution, carbonate content and current velocities for the Kunduchi area are used to determine its hydrodynamic setting and sediment characteristics. The sediment mean grain size generally decreases northward. The sediments consist of medium to coarse sand south of the Tegeta River and fine sand further north. The sediment sorting values, which lack a northsouth trend, vary from moderately well sorted to poorly sorted. The skewness of the sediment vary from near-symmetrical to very negatively skewed while the peakedness (kurtosis) varies from platykurtic to leptokurtic. The carbonate content increases with distance offshore, whereas the siliciclastic component decreases with distance offshore. The siliciclastic/carbonate transition of the investigated area is characterized by a narrow transition with no inter-fingering of the two facies. The lack of inter-fingering of the two facies suggests that there is a limited offshore transport of land-derived sediments. This is further supported by the drogue experiment results, which shows that the predominant surface current flows northward irrespective of the tidal phaseItem Sediment sources and their Distribution in Chwaka Bay, Zanzibar Island(WIOMSA, 2007) Muzuka, Alfred N. N.; Shaghude, Yohanna W.; Wannäs, Kjell O.; Nyandwi, NtahondiThis work establishes sediment sources, character and their distribution in Chwaka Bay using (i) stable isotopes compositions of organic carbon (OC) and nitrogen, (ii) contents of OC, nitrogen and CaCO3, (iii) C/N ratios, (iv) distribution of sediment mean grain size and sorting, and (v) thickness of unconsolidated sediments. The Chwaka Bay is located on the eastern coast of Zanzibar Island and is about 50 km2. It is a shallow partly sheltered lagoon with large intertidal area and fringing mangrove forest. The stable isotope values of nitrogen and OC, which averages 1.5±0.9‰ and -17.5±2.3‰ respectively, increases offshore indicating decrease in the influence of terrestrial material. Furthermore, nitrogen isotope values ranging from 0.3 to 3.9% suggest that the values result from nitrogen fixing plants. Because the bay has high abundance of calcareous green algae Halimeda plants, most likely low δ15N values reflect the influence of this photosynthetic plant to the total sediment budget. This inference is supported by low C/N ratio values that averages 7.9 ± 1.4 and with highest values being confined close to the mangrove forest. The contents of OC and nitrogen, which averages 0.75±0.60% and 0.11±0.08% respectively, are highest close to the mangrove forest. The sediment thickness in the Bay is higher in the northern part than in the southern part. The character of sediments in terms of grain size differs between eastern and western parts of the Bay. The eastern part is characterized by medium to fine white carbonate sand with mean grain size higher than 2φ, whereas coarse sediments with mean values less than 2φ characterize the western part. The content of calcium carbonate is very high with values being higher than 90% for the whole Bay owing to high concentration of carbonate sand-forming Halimeda.Item Shore Morphology and Sediment Characteristics South of Pangani River, Coastal Tanzania(WIOMSA, 2004) Shaghude, Yohanna W.Shore morphology and nearshore sediments between the Pangani and Kipumbwi rivers in coastal Tanzania were investigated. The information was gathered using field observations, sediment sampling of the area, and interviews with Pangani residents. The distribution of sediments on the sea bottom is mainly controlled by bathymetry, with sand (medium- to coarse-grained) dominating water depths less than 10 m, and silt dominating depths greater than 15 m. Sediments in water between 10- and 15-m depth consist of a mixture of fine sand and silt. The carbonate production in the study area is limited by the high influx of siliciclastic sediments from the Pangani, Kipumbwi and Ushongo Mabaoni depo-centres. While previous studies attribute the disappearance in the 1970s of Maziwi Island off the Pangani River mouth to sea level rise, the present study argues that anthropogenic influences may have been the major cause; if indeed the vegetation on the island was cleared as is reported, this could have hastened its disappearance. Sea level rise is also considered to be one of the potential threats to the survival of small islands like Maziwi.Item Shoreline Change in Tanzania and Kenya(Wiomsa, 2014) Shaghude, Yohanna W.; Mburu, J. W.; Arthurton, RussellShoreline change is an ongoing issue affecting communities, their livelihoods and tourism development in the Western Indian Ocean (WIO) region. A particular concern has been the threat of coastal erosion to tourism infrastructure. Other concerns, arising both from coastal erosion and from efforts to control it, include habitat loss and the degradation of coastal amenities. In Tanzania and Kenya, the issue of shoreline change, and in particular the hazard of coastal erosion, has been the subject of regional and national reports, identifying a range of possible forcing factors. Despite these efforts, there is a lack of guidance on the methodologies for the assessment and mitigation of the risks from shoreline change, both to affected stakeholders and to the coastal environment. The WIOMSA MASMA programme has therefore sought to promote and facilitate the development of such guidance by supporting an intensive study of shoreline change, its causes, socio-economic and environmental consequences; and the management of the associated risks to coastal communities. This manual reflects the outcomes of this study. The fieldwork focused on two case-study sites; one in Kenya on Mombasa’s northern shore, and the other in Tanzania on the shore of Msasani Bay, on the northern outskirts of Dar es Salaam. The sites include many of the typical physical, ecological and socio-economic features of these countries’ shorelines. They were selected on the basis of known shoreline change issues of economic significance. The compilation of the manual has benefited greatly from many national and international publications dealing with coastal management and, specifically, shoreline change and its physical processes. The illustrations, figures and data relate mostly to the case-study sites. However, the issues addressed are common to most coastal areas of Tanzania and Kenya, and some of them to the coasts of the WIO region as a whole