The scheme, which is billed as a regeneration and humanitarian project, covers an area in the heart of the city and extends into the eastern suburbs.
Lyn Edwards, the GMW senior partner who liaised with the Kenyan government on the plans, said the practice had learned from waterfront designs in other cities.
He said: "This is a huge project in the centre of the Kenyan capital. It could feature combinations of sea, docks and canal as in Cape Town, Boston, or on the Manchester ship canal."
The masterplan will provide about 2000 affordable homes on a disused airport. It will also provide for the regeneration of a five-mile stretch of the Nairobi River. This will involve landscaping, mixed-use developments and work to reducing pollution in the river.
The brief, entitled "Nairobi Intervention 2003", also involves the creation of a transport interchange around the central railway station.
The scheme marks a further step in GMW's strategy of penetrating Middle Eastern and African markets through "affiliation" – that is, by pooling resources with local firms on overseas projects.
GMW is working with Planning Systems and Services of Nairobi and Arup. About £600,000 of initial funding has been provided by the Kenyan government, which wants the scheme to be a public–private partnership. The total cost of the project has yet to be finalised.
GMW has several other projects on the ground in Africa. It is working with South African firm EHH on the construction of a deputy high commission in Cape Town, and with DAJ Architects on a £100m spa hotel in Ponto D'Ouro, in Mozambique.