Mont Cascades road drainage project

The Mont Cascades 2017-18 road drainage project entailed improving the performance of the road culverts and ditches along Chemin Panoramique and Rue du Soleil, a distance of approximately 3 km. This was the first such venture undertaken by the property owners association that was organized in the early '90s and it showed by not considering:

• • the overall Mont Cascades drainage system, especially as it relates to the volume and force of its many seasonal streams,

  • the type of soil and rock along the roads that would have environmental (leda clay) and cost (igneous rock slabs) consequences,

  • how to protect the quality of the water that would be drained into the river from the ditches,

  • how to conserve and enhance natural features that could assist with overall drainage,

  • how stormwater could be treated as a valuable resource,

  • the best sequence for doing the actual work, namely:

    1. engineer new or enhance existing areas to support natural water flow,

    2. make sure road culverts function properly,

    3. remove any rocks impeding water flow in ditches,

    4. deepen ditches where necessary.

The outcome only considered 2, 3 and 4 which were done in reverse order with the unfortunate consequences that ditches conveyed more water at greater velocity from the Oct 30 100mm 24 hour storm than the old road culverts that had not yet been upgraded could accommodate..

Strength of seasonal streams flowing from top of Mont Cascades

Some October 30th, roadside views after the 100 mm, 24 hr. rainfall. All pics were taken mid-afternoon about 5 hrs after rain had stopped. (click pics to enlarge).

All streams were very flashy. At runoff peak around 8 a.m, water volume was spectacular then diminished quickly when the rain stopped in late morning. The above is water in the seasonal stream entering and leaving last year's replacement culvert on Panoramique near Pierre's property.

Inadequately prepared culverts

Old rusted and damaged 12" under sized culvert half full with sediment with no functioning catchment basin at culvert's entrance quickly resulted in road erosion such as 200 Panoramique. This property is unique in draining into 3 seasonal streams. Vegetation at left was intended to help filter water as it entered ditch.

Ditch at du Soleil and Colleen on Sundary, Oct. 29 with a half full culvert of sand.

Eroding leda clay

Road erosion at du Soleil and de la Colline and the completely plugged 12" under sized culvert exit with water flowing from the road rather than the culvert.

Leda clay embankments in many of the ditches showed signs of erosion

Sediment loaded ditch water

Ditch water loaded with sediment only a short distance from the Gatineau River

Leda clay sediment

A Nov. 3 survey showed that a newly engineered ditch through leda clay (which replaced a well functioning soakaway swale) caused excessive sediment a mouth of a road culvert approximately 100m from river.

Summary

It was a bad day for the Gatineau River from all the untreated stormwater flowing into it, but thanks to Pierre it demonstrated his ability to quickly respond and get the roads re-opened by mid-afternoon.

Thoughts on the future

Is it really wise to facilitate a stronger flow of untreated water into the Gatineau River? It took Ottawa over 100 years to learn that this was undesirable and we already know that bad things can happen to the river from not properly managing the runoff from the former Marina Road. The City of Ottawa and other enlightened municipalities across Canada and NGOs like Green Communities Canada and Ottawa Riverkeeper know that it's best to work with nature at the water's source and along its drainage path by:

• • SLOWING the water down

  • SOAKING the water into the ground

  • CLEANING the water

Sunnyside Avenue in Old Ottawa South illustrates the use of rain gardens to improve water quality and reduce runoff into the Rideau River. They consist of soil, plants, and mulch on a foundation of granular stone to treat and absorb storm water run-off. The gardens trap-capture dirt run-off from the road and treat up to 25 millimetres of rain at one time.

We have many natural features that could help treat the quality of our storm water while at the same time helping to protect and enhance our trees and vegetation as well as contributing to our aesthetic appreciation and enjoyment.

Subscribing to the Umbrella newsletter provides lots of stimulation for the type of storm water management strategies we should be striving for.

Community Association Response

"Thanks for your pictures. They clearly demonstrate the importance of having gullies and well-maintained culverts, both of which were integral to the maintenance plan unanimously endorsed last year by the Association.

What you are proposing is a very different approach, one that could possibly work in a city but doesn’t really apply to our environment. You have been experimenting with this approach in front your property, with the unfortunate result that we saw yesterday.

You should be aware that the plan endorsed by the Association is also informed-based – i.e. founded on advice from civil engineers and my own professional knowledge as a geographer with a masters in hydrology.

The Executive Committee has a clear mandate from the Assembly and, therefore, we hesitate to shift gears completely mid-term. However, should members wish to support your vision, the Executive Committee will call an extraordinary meeting and I will step down."

The Executive Committee's negative attitude towards the environment will make it challenging to maintain an artificially imposed road drainage system on a 232m - 392m high hill with a well established drainage system that has existed for the past 11,000 - 12,000 years.