AUSTIN, Texas -- Austin leaders expect to add another 90,000 new residents by the year 2020. Already, Austin's outskirts have seen big population spikes.

Data collected by the City Demographer and City Auditor found Districts 2, 5 and 6 grew by 27,000 people between 2010 and 2015. The 10 City Council districts were drawn from 2010 US Census data, when each had roughly 80,000 residents.

"The areas of rapid growth in the City of Austin are in the suburbs," District 6 Council Member Jimmy Flannigan said. "You cannot sprawl your way to affordability."

Between 2015 and 2020, city officials estimate Districts 1, 2 and 5 will see the most new residents with an overall Austin population approaching 950,000.

Some of District 5's growth has been due to redevelopment along South Lamar.

"It's almost like, with District 5, we are seeing all kinds of impacts of growth, all kinds of impacts of affordability," Council Member Ann Kitchen said. "We are seeing folks having to move further south for affordability."

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Kitchen worries infrastructure won't be able to keep up.

"The questions are raised about, can the road handle it? Can the water and wastewater infrastructure handle it,'" she said. "We are caught between a chicken and egg kind of thing in terms of the growth and the impact on our infrastructure."

Affordability's also a concern. While the bulk of Austin residents make between $35,000 and $75,000 a year, 24-percent of the population makes more than $100,000. A considerable amount--almost 13-percent--brings in less than $15,000 a year.

Kitchen said moving further out may end up costing families more overall.

"It's more affordable, but it still comes at a cost of transportation cost and infrastructure cost (for the city)," she said.

The report also looked at family expenses. It found the average renter spends $50,580 a year on housing, food, transportation, retirement and other household expenses. The average homeowner spends $61,840 a year.