I think you are forgetting about markets, supply and demand. If a semi-detached or row house doesn't make economic sense in Deer Run, it won't be built in Deer Run regardless of the zoning.
But if it does make sense, let the market decide where and when this incremental intensification stuff occurs, an arbitrary 1 unit per lot rule imposed by the government is way too heavy--handed when we are only talking about adding 2, 3 or 4 units. There is no justification for that level of micro-management by government. The development process will still be required for all the infrastructure, safety and building code stuff.
On this location in Deer Run specifically, even if incremental growth occurs it won't cause crippling traffic in Deer Run because of two reasons:
1. Population remains 21% below peak population of 1998, or about 2,300 people.
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2. Bow Bottom Trail SE was originally designed to be Deerfoot's southern extension before Fish Creek Park was established. As such, it's design like a high capacity freeway and has several multiple times more capacity the car volumes it sees as it doesn't connect to anything. The last traffic count I could find on Bow Bottom in this area was in 2013, and estimated 11,000 cars a day (6,000 NB, 5,000 SB). This makes this road less busy than 33rd Ave in Marda Loop, a 2 lane road.
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Even if purely car-dependent, and a lot of houses turn over from 1 unit to 2 (or 3 or 4), there's no scenario in which these roads reach any sort of capacity limit. But not all houses will turn over, and all this will happen only over a long period of time so it's a moot point.