Don’t blame tile drainage for flooding

Re: Extreme weather ravages cities’ budgets, Sept. 24.

Pontiac Mayor and winery farmer Joanne Labadie claims “humans have made flooding worse because farms are now tile-drained,” attributing water from her north field, near the base of Lusk Falls, as the cause of a sinkhole on Highway 148. “That land that used to absorb all the water — it now rushes out very quickly,” she said.

Tile drainage of land facilitates rain absorption by movement of water through soil instead of prolonged surface ponding. This subsurface drainage draws water and air down root fibre channels of soil, carrying dissolved fertilizers for absorption by clay particles and organic matter of the soil for later absorption by crop roots. The water that emerges from tile drainage is clear and colourless, having been filtered by the soil, clearly an environmental benefit compared to surface run-off carrying fertilizer and suspended soil (surface erosion).

Tile drainage works by gravity, and discharge from outlets slows due to back pressure as water levels in discharge ditches, creeks, municipal drains, etc. rise above outlet levels.

The rapid flow of the Pontiac tiling reflects its unimpeded outlet because of the nature of the terrain. In such situations, the outlet conduit should be extended to an area where water discharge will not cause washouts or sinkholes.

George Neville, Ottawa (associate member, Local 362, National Farmers Union)