Tuesday, January 12, 2010

On Streetscaping (iv) Drainage

The drainage problem …

The current geometry of streets has the highest point along the centre line of the street. Water drains to the curb, adjacent the sidewalk. Catch basins are located along the curb.
Where vehicles drive adjacent the curb, they trail a cloud of dirty airborne water and splash water and slush onto the sidewalk.

Where parking is permitted along the curb, vehicles block the snow from melting and pack it down into ice. Salt creates puddles of slush and ice at every driveway dip in the sidewalk, creating a hazardous and unpleasant pedestrian environment.
When bulb outs and parking bays are employed drainage problems can be worsened if ice and snow block the catch basins located along the sidewalk.

The drainage solution …

When streets are totally reconstructed, more care and attention can be paid to improving drainage for the benefit of pedestrians, cyclists, drivers, and facilitating city maintenance.

Catch basins should be located adjacent the travelled vehicular lanes rather than in the parking bays. This means for significant lengths of sidewalk, water drains away from the sidewalk out to the street. The catch basins are less likely to be blocked by snow or slush, and are exposed to street plowing. Sidewalk dips at driveways are less likely to puddle or ice/slush up. Pedestrian slips and falls should be reduced. Less salty water will penetrate the ground around streetside trees.

Locating catch basins between the travelled portion of the road and the parking bays makes it more difficult and expensive to convert the street back into more lanes of through traffic as the catch basins have to be relocated, curbs rebuilt, etc.

When reconstructing streets, care should be taken to locate catch basins where they are least likely to be blocked by accumulated snow or slush, are exposed to self-cleaning by passing vehicles pushing aside slush, etc.

Brick-paved parking bay drains outward from the sidewalk to the edge of the travelled portion of the street.

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