ON A trip to Port Harcourt in Nigeria last week, I spent half of my time in traffic jams. This gave me plenty of opportunity to survey the teeming streets and consider the virtues of the urbanisation a new crop of Africa experts extols.

Port Harcourt, the centre of Nigeria’s oil industry, is the fastest-growing city in one of the most rapidly urbanising countries. In the mid-1970s — the beginning of the oil boom in Nigeria — the built-up area of Port Harcourt covered less than 18km², but 20 years later, the urban area sprawled over nearly 90km².

According to the United Nations (UN) Human Settlements Programme, in 1953 just 10% of Nigeria’s population lived in urban areas — just more than 3-million people then. By 2015, it predicts, more than 50% of Nigerians will be in cities — more than 80-million people by present population estimates.

Port Harcourt, along with other Nigerian cities, has experienced unchecked urban growth that has left it bursting at the seams. Founded in 1913 as a port to export coal, the city was built by the British colonial administration to accommodate 5,000 people. It is now home to at least 2-million, with more arriving daily in search of opportunities.

The authorities say that only 10% to 20% of the city is actually planned.

Once known as the Garden City, Port Harcourt is overrun by traffic, informal housing, makeshift markets, illegal structures and potholed roads, which snake through the hordes of traders that line its edges. In a bid to deal with this urbanisation crisis, neglected over decades, Rivers State governor Rotimi Amaechi is driving the building of a new city, adjoining the old one, with the aim of the two becoming one unified urban area in time.

The first phase of the 50-year, multibillion-dollar project, drawn up by South African company Arcus Gibb and the state government, has already kicked off. Access roads are being built or rehabilitated, new primary schools have mushroomed and housing estates are emerging. The erratic power supply is being improved, water infrastructure is being built and storm drains are going in. An ambitious monorail project is in its early stages and information and communications technology infrastructure is being installed.

The old city is so crowded that it is difficult to do much more than patch it up at present. There were riots after hundreds of illegal structures in slums lining the waterways of the city were demolished to root out criminals and pave the way for infrastructure improvements. The governor, who says he lives on energy drinks and headache pills, stared down angry residents, saying the action was necessary to prepare the city for the future.

Similarly, in Lagos, slums are being eradicated to tackle the urbanisation problem in poorer areas. But congestion everywhere makes it difficult to relocate people. New development is, by necessity, moving further and further away from the congested mainland, where most Lagosians live. Land is even being reclaimed from the sea for a new, upmarket, multi-use development removed from existing urban areas.

The picture is similar in many African towns and cities. New investment tends to go into outlying areas because of the congestion of inner cities, further separating informal settlements from development. Local authorities in urban areas often lack the capacity and resources to tackle problems arising from poor town planning and much of such work falls to multilateral agencies and nongovernment organisations, which tend to move slowly.

Many analysts argue that Africa’s rapid pace of urbanisation is one of the factors driving economic growth, investment and the advancement of people.

While this might be true on one level, the other side of the coin is that one in three people in developing countries lives in a slum, the UN says. This represents as much a risk for Africa’s future as it does an opportunity.

The cost and scale of addressing the crisis of unchecked urbanisation is enormous. If people living in Africa’s urban areas are to have a decent future, politicians need to be mobilised sooner than later to plan ahead for the surge of humanity into areas they control rather than waiting for a crisis to force their hand.

• Games is CE of Africa @ Work, an African consulting company.