One of the reasons of urbanization in Pakistan is lack of industrialization. Large industrial units, if not located in and around a city, attracts educated people from cities into high quality islands where basic needs like education, health, security and environment exist in much better quality. Even profitable agricultural industries can be useful to shed the load from urban areas. The basic problem is that there are not many “decent” employment opportunities in Pakistan, and everybody runs towards the large cities to earn “something”. Bottom line, we need an economic revolution which would ultimately resolve the hazards in large cities, either by diverting the people away, or by management and planning.
A very nice article by Ayesha: Urbanisation in Pakistan and its consequences.