How can Nairobi River project be a success in the long-term?

Those who know Nairobi River well, can tell the filthy it was several months ago.

The ministry of environment has done a tremendous job- cleaning the river and rehabilitating the former glory.
(a)What are the best practices of maintaining a river cutting across human in habitation?
(b)Can the "filthy" river become a resource ? e.g.cafes along the river