PPS25, published last week, defines zones more clearly in the "sequential test" of whether land is suitable for development. It sets out for the first time which types of development may be placed in flood risk zones.
RTPI head of research Jenny Crawford said the policy statement is "a real step forward in the clarity of process for planners". But she added: "We are being asked to assess risk when we do not have all the information. We need databases on the risk of flooding in catchment areas."
The Environment Agency and local authorities that work with it will require funding for this, Crawford insisted. The RTPI also said it expects more detailed guidance on how permissions can be fine-tuned to reduce run-off in urban areas in next year's planning white paper.
Ian Walton, technical director at consulting engineers Bureau Veritas, said: "This guidance clarifies a lot of grey areas and is easier to interpret. It is also very clear about the role of the Environment Agency and local and regional authorities."
The latest figures from the agency show that 95 per cent of local authorities followed its advice where it objected to projects on flood risk grounds.
But in 30 per cent of cases where an objection was made authorities still did not inform the agency of their decisions, it complained.
Many developers are ignoring the requirement for flood risk assessments to accompany planning applications, the agency added. Unsatisfactory flood risk assessments made up 68 per cent of all objections, it found.
PPS25: Development and Flood Risk and High Level Target 5 Development and Flood Risk is available at PlanningResource.co.uk/doc.