WIXLIB

4V. MAKOTA ET AL.lines, which determine shoreline changes/recession,were calculated in ArcView. Shoreline changeresults are provided in the form of photomaps.Ground truthingGround truthing on the entire study area wasconducted for two days. The aim was to collectmore data and information from the field andinterview the people from the study area. Thepeople interviewed were asked about the status ofthe shoreline in relation to previous years. Theirresponses agreed well with our GIS analyticalfindings. A number of photographs were also takenof the study site using a digital camera in order tocapture the area’s current appearance. Thephotographs show some vivid examples ofshoreline erosion from the ruins of buildings thathad collapsed due to shoreline erosion, includingAfricana Hotel.stone structure constructed in order to controlshoreline erosion at the Kunduchi Beach Hotel.This stone structure was built after groynes failedto control shoreline erosion. The groynes can beclearly seen in the photomap that shows changesbetween 1981 and 1992.1981–2002About 2.62 ha of land were eroded from thenorthern part of the creek between 1981 and 2002(Fig. 2). The green line on the photomap representsthe shoreline in 1981 whereas the red linerepresents the position of the shoreline in 2002.The area between the two lines, labelled “A” onthe photomap, represents the eroded area. Fromthis photomap the current shoreline (2002) is veryclose to the Kunduchi Beach Hotel.Southern Kunduchi–Manyema creek1981–1992RESULTSNorthern Kunduchi–Manyema creek1981–1992The analysis on the shoreline change between 1981and 1992 is shown in Fig. 2. About 2.02 ha of landwere eroded from the shore in the northern partof the creek. The green line in the photomaprepresents the shoreline in 1981 whereas the blueline represents the position of the shoreline in1992. Between the two lines, labelled “B” in Fig.2, is the eroded area, which measures 2.04 ha.However, there had been an accretion of about0.11 ha at the same time in the area denoted by ablue letter “A”.1992–2002Figure 2 also shows the shoreline change between1992 and 2002. About 0.68 ha of land was erodedfrom the shore in the northern part of the creek. Ablue line in the photomap represents the shorelinein the 1992 whereas the red line represents theposition of the shoreline in the 2002. An area inbetween the two lines, labelled “C”, represents theeroded area. The area labelled “B” shows an areaof gain (accretion). However, this is not anaccretion from natural processes, but is a man-madeBetween 1981 and 1992 about 1.13 ha of land,labelled “C” in red, were eroded from the shore inthe southern part of the creek. The green line in thephotomap (Fig. 3) represents the shoreline in the1981 whereas the blue line represents the positionof the shoreline in 1992. There was an accretion ofabout 0.04 ha, labelled with a blue “B”, in thesouthern part of the creek over the same period.1992–2002There were considerable shoreline changes in thisarea from 1992 to 2002. There was less shorelineerosion (only 0.12 ha) in areas denoted “D” in redon the photomap shown in Fig. 3. However, therewas more accretion during this period, whichformed a continuous piece of land with an area of2.81 ha protruding northwards, which is labelledwith a blue “C”. During ground truthing weobserved vegetation such as bushes and someexotic trees species of more that 10 metres inheight within this area.1981–2002During 1981–2002 about 0.61 ha of land waseroded from the area labelled with a red “A” inthe photomap in Fig. 3. There was more accretionof about 2.21 ha in the area labelled with a blue“A”. Also, about 0.40 ha of mangrove was erodedin areas denoted with a red “B”.

Fig. 2. Shoreline change from 1981 to 2002 in the northern part of Kunduchi–Manyema creekMONITORING SHORELINE CHANGE WITH REMOTE SENSING AND GIS5

Fig. 3. Shoreline change from 1981 to 2002 in the southern part of Kunduchi–Manyema creek6V. MAKOTA ET AL.

MONITORING SHORELINE CHANGE WITH REMOTE SENSING AND GISOther parts of KunduchiFigure 4 shows the shoreline changes between1981 and 2002 at the former site of the AfricanaHotel to the south of Whitesands Hotel. The blue7and red lines represent the shoreline (highest watermark) in 1981 and 2002 respectively. The shorelinein 2002 is shown in red in the upper part of thephotomap but it has not been extended to thesouthern part, from point “A” southwards, whereFig. 4. Shoreline changes in other parts of Kunduchi shores between 1981 and 2002

8V. MAKOTA ET AL.land reclamation efforts can be seen in front of mostbeach hotels, as curved shapes on the shoreline.Letters A, B, C and D in Fig. 4 represent areaswhere measurements for shoreline change weretaken. At point “A”, near Beachcomber Hotel, theshoreline erosion that took place caused a recessionof about 52 m. At point “B”, we decided to measurethe distance from the shoreline to a point at a roadgoing to the former Africana hotel. It was foundthat in 1981 the shoreline was about 78 m fromthis point at the road. However, in 2002 theshoreline was 36 m from the same point. Thus, in21 years the shoreline has shifted by 42 m. At point“C” the shoreline changed by 29 m and at point“D” by 40 m.River mouth changes at Kunduchi–Manyema creekPoints “A” and “B” have been positioned in areaswhich used to be the nearest (end points) in thenorthern and southern parts of the river mouthrespectively. The distance between points “A” and“B” in Photo 1, Fig. 5 was about 79 m in 1981.The original positions of these points as they werein 1981 are displayed in the photomaps of 1992and 2002. The distance between points “C” and“D” also shows the width of the nearest pointsbetween the northern and southern points of theriver mouth in 1992, which was about 325 m.DISCUSSION AND CONCLUSIONThe present study used remote sensing data andGIS to quantify shoreline change in Kunduchi area.It has been observed that shoreline change in thestudy area results from both erosional andaccretional processes. The study has revealed thatduring 1981– 2002, more erosion took place in thenorthern part of the creek while deposition tookplace in the southern part.Between 1981 and 1992, about 2.04 ha wereeroded from the northern part of Kunduchi–Manyema creek. This area increased to more than2.60 ha by 2002. Some of the buildings hadcollapsed near Kunduchi Beach Hotel, especiallyin areas close to the fish market, causing damageand loss to property and investments.Previous efforts at controlling coastal erosionthrough the construction of groynes do not seemto have been effective. Some of the groynes havebeen washed away and others stand far from thecurrent shoreline, showing that erosion is stilltaking place. As a mitigative measure, KunduchiBeach Hotel has recently constructed stonestructures.Despite the general observation that erosion issignificant in the north and deposition in the south,the present study found that there are some partssouth of the Kunduchi – Manyema creek that havebeen significantly been affected by erosion. Inaddition to collapsed properties, shoreline erosionremoved the mangroves on the southwestern side,especially between 1981 and 1992. About 0.4 haof mangroves was washed away along the riversidenear the river mouth. The people interviewed alsomentioned the mangrove removal in this area.From the aerial photographs it appears thatserious shoreline erosion at the river mouthoccurred between 1981 and 1992. From the 1992aerial photograph, the river mouth widened toabout 325 m from its previous width of 79 m at itsnarrowest point, between “A” and “B” in aerialphotograph of 1981. Although there was accretionat that time, it has been difficult to determine theextent of these depositional features from theblack-and-white aerial photographs used in thisstudy. There is almost no contrast between the toneof beach and sand deposits. Nevertheless, it hasbeen possible to determine shoreline erosion basedon the pattern and texture of the land/water areasin relation to the river passage. The fishermeninterviewed also helped to identify the featuresfrom the aerial photographs during fieldwork.Accretion is taking place in the southern partof the creek. As a result, this part of the creekprotruded northwards from the former site of theAfricana Hotel forming a piece of land of about2.81 ha between 1992 and 2002. According tomeasurements using GPS, an area of about 2.24ha from this land is covered with vegetation, suchas trees and bushes. In fact, there is more vegetationthan was present in 1981. It appears that the soilcharacteristics have changed and this parcel of landhas stabilised, but further monitoring isrecommended.Continued monitoring of shoreline changes isimportant to our understanding of the changestaking place at the Kunduchi–Manyema creek and

9Fig. 5. River Mouth Changes at Kunduchi–Manyema creekMONITORING SHORELINE CHANGE WITH REMOTE SENSING AND GISthe Kunduchi shores in general. Furthermore,studies that link land use patterns, hydrologicaldata, human activities and other processes takingplace in the coastal and marine areas arerecommended. The results of this study should beintegrated with other datasets in a GIS in order tomonitor changes in the future. It is also importantthat these results be shared with relevantstakeholders, including coastal managers, investors(particularly hotel owners), the public, policymakers, researchers and other scientists, for usein decision-making on such issues as land useplanning, development of set-back lines andidentification of low-cost methods which couldbe used in the context of integrated coastal areamanagement. It is concluded that remote sensingand GIS are useful tools for monitoring the coastalenvironment and resources in Tanzania.

10V. MAKOTA ET AL.Acknowledgement—We appreciate the assistanceprovided by the Tanzania Coastal ManagementPartnership (TCMP) in terms of facilities, logisticalarrangements and also financial support during thestudy.REFERENCESBanyikwa, F.F. & Semesi A.K. (1986) Endangeredmangrove ecosystems—the case of Kunduchi andMbweni mangrove forests. In: Mainoya, J.R. &Siegel P.R. (Eds.), Status and utilization ofmangroves. Proceedings of a Workshop with thetheme Save the Mangrove Ecosytsem of Tanzania,21–22 February 1986. Dar es Salaam. Faculty ofScience, University of Dar es Salaam. pp.103–132.Benno, B.L. (1992) Some features of beach seinefishery along the Dar es Salaam coast, Tanzania.MSc thesis, University of Kuopio, Finland. 68 pp.Bryceson, I. (1977) An ecological study of thephytoplankton of the coastal waters of Dar esSalaam. PhD Thesis. University of Dar es Salaam.Fay, M. (1988) Ancient backshore sediments betweenBahari beach and Mbezi beach. In: Beach ErosionAlong Kunduchi Beach, North of Dar es Salaam.A Report for NEMC by Beach Erosion MonitoringCommittee, 55 pp.Griffiths, C.J. (1988) The impact of sand extractionfrom seasonalstreams on erosion of Kunduchibeach. In: Beach erosion along Kunduchi beach,north of Dar es Salaam. A Report for NEMC byBeach Erosion Monitoring Committee. 55 pp.Griffiths, C.J. & Lwiza, K.M. (1988) Physicalbackground of the study area. In: Beach erosionalong Kunduchi beach, north of Dar es Salaam. AReport for NEMC by Beach Erosion MonitoringCommittee. 55 pp.Hartnoll, R.G. (1975) The ecology of some rocky shoresin tropical East Africa. Estuar. Coast. Sci. 4: 1–21.Howarth, P.J. & Wickware, G.M. (1981) Proceduresfor change detection using Landsat digital data. Int.J. Remote Sensing 2: 277–291.Jensen, J. R. (2000) Remote sensing of the environment:An earth resource perspective. Prentice Hall.Kairu K. & Nyandwi N. (eds.), (2000) Guidelines forthe study of shoreline change in the Western IndianOcean region. Manual and Guides.Intergovernmental Oceanographic Commission,UNESCO.Lillesand, T. M. & Kiefer, R. W. (1994) Remotesensing and image interpretation, 3rd ed. JohnWiley & Sons.Linden, O & C. Gustof, (1995) (ed.) Coastal ZoneManagement in Tanzania. Proceedings of theNational Workshop on Integrated Coastal ZoneManagement in Tanzania. The World Bank: Land,Water, and Natural Habitats Division. May, 8–12.Lugoe F.N. (2003) NSDI— A look at the spatialdimension in Tanzania: Unpublished report.Mushala, H. M. (1978) Coastal processes alongKunduchi Beach. In: Dubi A. 2000 (Ed). CoastalErosion. Tanzania Coastal ManagementProgramme. Dar es Salaam.Muzuka, A.N.N. & Shaghude, Y.W. (2000) Grain sizedistribution along Msasani beach north of Dar esSalaam harbour. J. Afri. Earth Sci. 30: 417–426.Mwaiseje, B. (1973) Some aspects of the ecology ofsandy/muddy intertidal zone in Dar es Salaamarea. MSc thesis. University of Dar es Salaam.103 pp.Okera, W. (1971) Plankton analysis relative to thefeeding habits of Sardinella in Dar es Salaamwaters. PhD thesis, University of Dar es Salaam.212 pp.Persons, M.P. (1988) Coral reef resources in the Dares Salaam area. In: Investigations Related to theProtection and Conservation of Coastal MarineResources in Dar es Salaam Area. NEMC/UDSM/IMS/TAFIRI/Fisheries Division. pp. 12–35.Semesi, A.K. & Shushu, D. (1988) A survey ofseagrasses and seaweeds along the Dar es Salaamcoast. In: Investigations Related to the Protectionand Conservation of Coastal Marine Resources inDar es Salaam Area. NEMC/UDSM/IMS/TAFIRI/Fisheries Division. 36–62.TCMP (1977) An overview towards intergrated coastalmanagement. Tanzania Coastal ManagementPartnership brochure.

Figure 2 also shows the shoreline change between 1992 and 2002. About 0.68 ha of land was eroded from the shore in the northern part of the creek. A blue line in the photomap represents the shoreline in the 1992 whereas the red line represents the position of the shoreline in the 2002. An area in between the two lines, labelled "C .