The announcement came as scientists said flooding from a swollen River Thames could last for several weeks, the Guardian reported.
Hammond announced the deployment after Surrey volunteer flood warden Su Burrows pleaded for help from the army.
Burrows told Hammond she and otter volunteers had worked together to rescue people from 100 homes in the previous 48 hours, but that emergency services officials "don't take us seriously."
Fourteen severe flood warnings remained in place along a 12-mile stretch of the Thames in Berkshire and Surrey counties in the southern and southeast regions of the country. Across England and Wales, more than 130 flood warnings had been issued.
In Surrey, Chief Police Superintendent Matt Twist warned rising waters endangered about 2,500 homes and officials said residents of the area should be prepared to evacuate if urged to do so.
Flood warnings were northward, with amber "be prepared" warnings issued for Yorkshire in northeast Britain.
The national weather agency, the Met Office, offered no respite from the wetness. It told residents of southwest and southern Wales to prepare for strong winds and more than an inch of additional rain.
Even as southern England was awash in water, the Automobile Association warned drivers in northern regions to watch out for snow. Driving conditions on the higher routes in Derbyshire, Yorkshire and Lancashire were described as "very tricky." Police in Wales also warned of heavy snow along the coast.
Flooding from the Thames could last for "a substantial number of weeks," said Terry March, a hydrologist at the Center for Ecology and Hydrology in Wallingford, noting the river was experiencing the highest sustained flows since 1883.
Prime Minister David Cameron warned Britons conditions would not return to normal quickly, but the government would act as quickly as possible.
"We are in for the long haul but the government will do everything it can to coordinate the nation's resources," he said.
Labor Party leader Ed Milliband called the situation a "wake up call" for more funding for flood defenses.
"Clearly this kind of extreme weather is going to be more likely in the future with climate change," he told Sky News.
Damage from the flooding could approach $1.6 billion, accounting firm PwC said Monday.