The utilisation of satellite imagery and community perceptions to assess the impacts of sea encroachment in the West Coast of Cameroon at Limbe

Mabel Nechia Wantim,Samuel Ndonwi Ayonghe,Louis Jitiz,Wase Albright Mokosa

doi:10.4314/jcas.v16i3.3

Abstract

Coastal erosion associated to sea encroachment is a major problem at the West Coast of Limbe, specifically in the Debundscha Fishing Port (DFP). This study sought to assess the physical vulnerability of the West Coast of Limbe to coastal erosion associated to sea encroachment. This was achieved by assessing: i) the physical vulnerability of the West Coast to coastal erosion; ii) land cover changes and iii) community perception at DFP to sea encroachment and coastal erosion in the past 30 years. Three variables: rock type, adjacent land use and coastal protection were used to assess the vulnerability of the West Coast to coastal erosion. Landcover / coastal changes were assessed from satellite images from 1986 to 2018. Semi-structural interviews were used to acquire knowledge on the population’s perception and impact of the studied hazards. A cost benefit approach was used to weigh the potentials of these localities to adapt to coastal erosion. The DFP and Idenau Beach were identified as major hotspots of coastal erosion with an annual rate of >100 m². Landcover changes showed a net increase in water levels inland and into settlements. The population is knowledgeable and is aware of the risk of sea encroachment and coastal erosion. The physical, socio-economic and health effects were: destruction of mangroves;relocation; malaria, typhoid and abdominal illnesses respectively. Coping strategies included the use of sandbags, building on higher grounds and on embankments. Cost benefit analysis ranked vegetative cover as the best option environmentally and financially viable to reduce coastal erosion from sea encroachment at the West Coast. Key words: Sea encroachment, coastal erosion, physical vulnerability, perception, Debundscha Fishing Port

Highlights

40 % of the world’s population is within 100 km of the coast (Wong et al, 2014; Neumann et al, 2015) which host the main economic hubs of most countries (NOAA, 2017; Ayyam et al, 2019)
Debundscha Fishing Port (DFP) is one of those areas along the West Coast which has been hardest hit by sea encroachment and coastal floods
2.3 Methods 2.3.1 Vulnerability analyses to coastal erosion To determine the level of physical vulnerability of the West Coast to coastal erosion three variables were considered: i) geomorphology, ii) adjacent land use and iii) adaptation measures

Summary

Introduction

40 % of the world’s population is within 100 km of the coast (Wong et al, 2014; Neumann et al, 2015) which host the main economic hubs of most countries (NOAA, 2017; Ayyam et al, 2019). Globally, coastal zones are facing a good number of intensifying changes like sea encroachment, coastal erosion and floods stemming from natural and anthropogenic factors. Managing coastal flood risk is a crucial aspect since it affects developments, and is becoming increasingly important for coastal communities (Wadey et al, 2015; Vousdoukas et al, 2016, 2018). Bird (2008) and Zhang et al (2000) identified crucial factors for coastline change (e.g. geomorphology, wave action) and continuous beach erosion (e.g. sea level rise (SLR), human interference). Humans enhance sea-level rise through climate change, destruction and altering of coastal natural defences, over exploitation of coastal resources and continuous proliferation of settlement concentration (Domingos, 2016; Woodward, 2019). The human variables, land use and artificial coastal protection, contribute to coastline erosion (Pendleton et al, 2005)

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