A natural flood management scheme saved a North Yorkshire town from floods at Christmas, a report says.
The pioneering scheme slowed river peak flow by 15-20%, saving Pickering's museum and several homes, Environment Agency (EA) analysis revealed.
More than 2ins (5cm) of rain fell in the area over 36 hours from 26 December.
Pickering has suffered four serious floods in the past 10 years.
However, the EA warned the scheme that saved it last winter would not work in extreme rainfall.
It had decided to experiment with catching rainfall in the hills because building flood walls high enough to protect the town is difficult.
Long, low, leaky dams were installed to slow the flow of water off the slopes.
An upstream flood storage reservoir was also installed, along with the planting of 40,000 trees and the restoration of heather moorland, which acted as a sponge.
The report estimates around half of the reduction in flood water in Pickering was due to the upstream land management measures, and half due through the effect of the flood storage area.
The EA said more tests needed to be done to be certain about the results.
John Curtin, EA's director of flood risk, said: "Natural flood risk management measures, when used alongside more traditional flood defences, can make an effective contribution to reducing flood risk, as demonstrated in Pickering.
"They can also deliver more benefits than just reducing flood risk such as improving water quality, preventing erosion and in some cases storing carbon."
Environment Secretary Elizabeth Truss said the Slow the Flow scheme had used nature for protection in "a truly innovative way".
"Natural and man-made defences both have a role to play in reducing flooding, but every approach must be tailored to local geography and knowledge," she said.
Ms Truss is setting out a 25-year plan for the environment, looking at the management of river catchment areas as a whole, to improve flood resilience.
A recent report suggested re-foresting up to 40% of river catchments could help prevent floods.
The EA report comes as two parliamentary committees prepare to quiz ministers about their future strategy for preventing floods.
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