On Tuesday, the Beijing Water Authority released a map of roads that were swamped (http://t.cn/zWSQv2I), and asked residents to avoid those areas in future major storms. Beijing's worst rainstorm in 61 years was responsible for at least 37 deaths and stranded countless motorists on roads. Weather forecasts said the municipality could be hit by more heavy rain on Wednesday night and today.

The water authority mapped out 30 road sections where the rainwater had been more than 30 cm deep, and 33 road sections where the water was less than 30 cm.

Most of the road sections where the water was deeper than 30 cm were at low-lying intersections. The majority of these sections were on the municipality's Second Ring, Third Ring and Fourth Ring roads. More road sections were flooded in the southern part of the municipality than in the north.

The municipality's map went online after several similar homemade ones. The online campaign was initiated at Guokr.com, a social network website for science fans.

Registered users at the website shared their experience of the flooded roads. A netizen with the Internet name of "goldengrape" compiled the experiences and released a Google map of the roads and communities that had been flooded.

Forty places were labeled on his map as "danger zones" with details of dangers in specific areas, such as "manhole covers washed away".

Contact the writer at xuwei@chinadaily.com.cn.