Although the region experiences calm conditions through much of the year, sea-level rise and climatic variation may reduce the buffer effect of coral and patch reefs along the east coast, increasing the potential for erosion.
Growing coastal activities have attracted large populations to the coast and this has exerted big strains on coastal groundwater resources. For example, Dar es Salaam is heavily populated with over 85% of the industries situated in and around the city.
The depth to water-table in the coastal zone is often very shallow and is subject to saline sea water contamination and pollution. An increased global sea level rise is expected to raise the water-table along the coast and result in increased salinity of the groundwater.
Many of the island states are already experiencing this phenomenon and the situation is expected to worsen with sea level rise.
There are three response strategies to rising sea level and its physical impacts: RETREAT, ADAPT or DEFEND. In practice, many responses may be hybrid and combined elements of more than one approach.
Retreat can involve chaotic abandonment of property and cultural investments, or it can be an ordered, planned program that minimizes losses from rising sea level and maximizes the cost-effectiveness of the operation.
The operation also seeks to leave surrendered areas as aesthetic looking as possible and to avoid abandoned structures that are an operational hazard to other social and economic activities.
Adaptation/Accommodation – all natural system effects are allowed to occur and human impacts are minimized by adjusting human use of the coastal zone. For East African countries, adaptation is the immediate priority to respond to sea-level rise.
Defence/Protection – natural system effects are controlled by soft or hard engineering, reducing human impacts in the zone that would be impacted without protection.
The assessment of impacts of sea level rise over the next century is hindered by lack of knowledge of the detailed topography of the near shore.
New global elevation maps based on detailed surveys at cm resolution will make it possible to accurately determine the areas which will be inundated by storm surges under conditions of rising sea level.
This will require a concerted effort by the satellite altimetry community as well as local ground-based geodetic surveyors in all coastal areas world-wide.
