Varying factors can cause rural areas to become urban centers. Some of the causes include urban sprawl, development and availability of natural resources.
Proximity From The City & Urban Sprawl
Rural areas close to cities have close access to water, communication and power lines. As such development of nearby rural areas become much easier and can evolve into urban areas.
In addition, urban areas can expand outwards encroaching nearby villages and towns; a process called urban sprawl. Many rural areas have become cities in China due to urban sprawl (outward expansion).
Development by Local Government
Development by government initiatives can transition rural areas to urban.
For example, rural electrification and telecommunication line installations can accommodate rural urbanisation. Some of the areas in Zimbabwe include Chitungwiza and Seke.
Urban Decongestion
As a way of reducing strain and population in overburdened cities government can develop other rural areas to become urban centers.
For example, Mt Hampden in Zimbabwe was once a rural area but development is underway for it to become a major urban city with national parliament, central bank, courts, houses etc. This reduces strain on the capital Harare.
Availability of Resources
A rural area with abundant resources can create job opportunities for local people. These jobs can start small at a subsistence level and may evolve into big factories employing hundreds of people and can transition to an urban area.
Trading and Route Focus
Rural areas situated along transport routes can evolve into urban area.
These areas connect other towns and as a result accommodate trading and movement of goods.
One example is Ibadan, Nigeria. It was once a military center. Its location and railroad connected it with various towns making trading easy.
It now hosts a variety of commercial activities and urban houses.
Counter Urbanisation
People migrating from urban to rural areas can redevelop their rural houses to match urban standards. Overtime, this can result in rural urbanisation with urban standard houses and commercial buildings.
This is the case in some US states were people are moving from cities to rural areas. Urban standard houses are being built in rural counties.
In Zimbabwe more and more urban houses can be seen in areas like Seke