An Integrated GIS Method – The Influence of Human Activities on Shoreline Change in Western Indian Small Island States: A Two Centuries Analysis of Urban West Unguja - Zanzibar Shoreline

Abstract

Urban areas have a high impact of shoreline changes that are influenced by human activities rather than natural factors together with hard structural mitigation and management which are more practiced compared to other areas The shoreline of Urban West of Unguja Island in Zanzibar has been undergone changes in different stages due to human activities either like reclamation of Darajani creek port expansion at Malindi Mtoni beach nourishment sewer and stormwater channeling at Kilimani construction of walls groins and jetties etc however the area experience more accretion rather than retreat integrated analysis and projections of the overall accretion and retreat for 174 years is 1 527 693 85 m2 1 53 km2 and -936 135 48 m2 -0 94 km receptively The average accretion of land from 1846 to 2020 is 8 779 85m2 yr 0 0088 km2 yr and retreat is -5 380 09m2 yr - 0 0054 km2 yr A major accretion was observed and detected during the early 1900s to late 1987 where major land transformation with other minor development activities between 2010 to 2020 Sea walls groins beach nourishment mangroves barrier islands and islets are major management practices of the shoreline which shows positive impact Integrated methods were used to analyze and detect changes using a sketch topographic map and images which were carefully georeferenced with latitude and longitudes digitized using ArcGIS and demarcated along the study area supported with ground truth observation