Some wisdom from David Week on his architecture for development blog:
Urban migration is a necessary and good thing.
It’s essential to rural development, to urban development, and poverty reduction in an era in which people are being helped to live longer, but have not yet begun to reproduce less.
However, it cannot in itself create rural development, urban development or poverty reduction. It has to be steered by policies which accept it as fact, and base rural, urban and economic development on that fact.
The fact that migration creates slums is not the fault of the migrants, and the solution does not lie in attempting to prevent their arrival: a Quixotic goal akin to stopping a river.
Rather: Accept these immigrants, and welcome them by planning for their arrival through tenure, services, public transport, planned neighbourhoods, and the creation of economic opportunities.