Firefighters were called to five grass fires in fours hours at the same beauty spot.
Crews attended Darland Banks in Gillingham five times between noon and 4pm today.
Fires had been set in different places around the nature reserve, believed to have been started by children.
Crew manager Ben Fletcher said: "They were in different places around the banks, suggesting to us that it was kids mucking about.
"They were only small fires, the largest was around 20 sq m, but there is always the potential for it to be much worse.
"Fires can spread very easily, especially in this dry weather. It's also dangerous because of the slope of the bank, someone can light a fire at the bottom and it can rapidly spread up the bank towards other children or passers by."