Tropical storm Harvey hits Houston, thousands affected

Tropical storm Harvey hit Houston, the US' fourth-largest city, on Friday with a ferocity that sent thousands of people to rooftops or higher ground. Rescue personnel found themselves overwhelmed by the constant calls for help.

The storm shrouded the city in turbid, gray-green sheets of water and turned streets into rivers navigable only by boat.

The rescue effort was reminiscent of the aftermath of Hurricane Katrina, as helicopters landed near flooded freeways, airboats buzzed across submerged neighbourhoods and high-water vehicles made their way through water-logged intersections. Some people made good use of kayaks or canoes, while others swam.

Volunteers joined emergency teams to rescue people from their submerged homes. The water was high enough in places to gush into second floors. The flooding was so widespread that authorities had trouble identifying the worst areas and urged people to get on top of their houses to avoid getting trapped in attics and to wave sheets or towels to draw attention to their location.

According to federal disaster declarations, the storm has so far hit about a quarter of the Texas population, or 6.8 million people across 18 counties and has been blamed for at least two deaths.

Harvey made landfall as a category-four hurricane late on Friday and was later downgraded to a tropical storm.

Around 2,000 people have been rescued in and around Houston, where about 6.6 million people live in the metropolitan area.

In Washington, the Federal Emergency Management Agency (Fema) said it was committed to assisting in the rescue effort.

An estimated 30,000 people are in need of shelter and according to Fema administrator Brock Long providing shelter to 30,000 people in need was "going to be a very heavy lift".

He added that, with thousands of homes without electricity, the agency was also working to restore power and critical infrastructure.