The agency's Unison staff have joined thousands of their colleagues across the country in walking out and are staging a protest this morning at Frankwell in Shrewsbury – the location of the town's flood barriers.
The move is the first time Environment Agency (EA) staff have gone on strike over pay in the regulator’s history.
Unison said “the employer’s failure to give a decent pay rise has left them with no alternative”.
EA members were balloted for industrial action late last year, and voting overwhelmingly to take industrial action.
However, it has been agreed that officers will step in as emergency ‘life and limb cover’ where there is a threat to life or property from incidents such as a major flood, Unison said.
The strike sees workers, who maintain critical flood barriers and manage flood warning systems along the River Severn, walk out this morning at 8am.
They also attend river pollution incidents, manage, and monitor flood risk, waste crime fires, respond to drought, environmental incidents and fly-tipping incidents.
Adam Shipp, a Unison workplace rep who works for the Environment Agency, said: "Even though we turn out every year to protect the people of Shrewsbury, Shropshire and beyond from flooding, we have seen our pay reduced by over 25 per cent in real terms over the last 10 years.
"Our members should be properly compensated for turning out in all weathers and doing their utmost to stop properties flooding and protecting the environment, quite often around the clock and regularly for weeks on end.
"Government cuts, the cost of living crisis and below inflation pay rises mean we have over a thousand vacancies nationally and we’re on our knees. Staff have had enough, with some having to rely upon food banks and help from relatives."
Unison said that with the current rate of inflation at over 10 per cent Environment Agency staff have been offered a two per cent rise, as well as an unconsolidated payment of £345.
Unison head of environment, Donna Rowe-Merriman, said: “The decision to strike wasn’t taken lightly as workers know their role is crucial in keeping communities and the environment safe."
She added: "The lowest-paid workers are truly struggling to make ends meet and this appalling situation cannot go on.
“Communities rely on these critical workers, particularly during bouts of extreme weather and rising problems of river pollution. They should be paid accordingly. Therefore, the union is urging ministers and the Environment Agency to negotiate and give workers an improved pay offer to avoid more staff 'joining the exodus'."