Toronto is vulnerable to flooding so prevention planning is an important topic. One groundbreaking retrofit solution is the use of permeable pavement, which University of Guelph Prof. Andrea Bradford, School of Engineering, discussed in a Toronto Star article. She explained how the multilayered system drinks in rainwater and cleans it of sediments and pollutants. Although permeable pavement can be used in residential areas for parking lots, driveways, shoulders, streets and sidewalks, Bradford points out that it is not an option on roads with heavy traffic. Bradford, who has experience with the Water Policy Branch of the Ontario Ministry of the Environment, teaches and researches urban water systems, low-impact development, ecological flow assessment, and stream and wetland restoration.