The Prime Minister has been criticised for failing to visit areas flooded by intense rainfall earlier.
Some onlookers shouted "traitor" at Mr Johnson as he arrived on the banks of the River Severn in Bewdley on Sunday afternoon.
One woman asked the PM: "Are you about two weeks too late?"
When Mr Johnson was asked why he did not visit flood-hit communities when the waters were at their peak, he responded: "It's too easy for a PM to come to a place in a middle of an emergency, it's not so easy frankly for the emergency services.
"What they have to do is then break off and gold command has to find somewhere to brief you, everybody has to gather.
"They're diverting from their work for hours and hours.
"What I've been doing since the flooding began is coordinating the national response but also looking at what we can do in the next months and years to ensure this country really is ready to cope with the impacts of flooding."
Bewdley has been among the worst-hit areas in England following the wettest February on record.
Mr Johnson said he would “get Bewdley done” as he spoke to residents affected by the floods.
He said he was “so sorry to hear it” when he heard homes had been overwhelmed by as much as 2ft of water.
Mr Johnson received a mixed reception as he walked through Bewdley town centre.
While a number of teenagers asked him to stop for a selfie on the bridge, and he happily obliged with a smile and a thumbs up, as he walked back on to the river bank, one man shouted "do your f****** job".
But other residents mobbed the Prime Minister and tried to shake his hand and take photos as he made his way along the river.
He met with members of the emergency services who responded when the water levels rose and told them the defence structures in the town were "pretty amazing".
But the Prime Minister said he had discussed with Environment Agency officials what "permanent defences" can be installed.
He said: “What we’re doing is we are doubling the funding for flood defences to £5.2 billion and we’re also going to be looking at all the things we can do upstream.”
Mr Johnson was also asked how flood-hit communities can feel reassured because the barriers did breach, he replied that the issue was that water had come over the top of them.
"The problem with these barriers is that they were overtopped," Mr Johnson said.
"They are great bits of kit but when you have a big flood like that, they're not going to be effective.
"The things we have to look at are the rules which currently say that you can't put in permanent defences when you've only got a small number of households potentially affected.
"The case we need to make is it's not just the number of households, it's also the economic damage, it's the damage to confidence, all the rest of it in the town."