Millar Channel proper begins just South of Ahousat village on Flores Island and stretches up to Obstruction Island. This analysis also includes the water along the North coast of Flores Island that is officially considered as part of Shelter Inlet (see maps below for context map). The measured portion is about 31km long, and it ranges from 1.5km wide to a choke point of about 0.25km along Obstruction Island. The deepest point is just to the South of Obstruction Island at nearly 150m deep, with another deep point at 123m deep on the West side of Obstruction Island. The shallowest sill is one of the closest point to the ocean, just to the East of Ahousat village and is a mere 5m deep. There is also a sudden incline through the choke point by Obstruction Island that shrinks to 15m deep between the two deepest points in the channel. This area was formed in the same way as the rest of Clayoquot Sound: tectonic activity brought the Earth's crust upwards, volcanic activity built up islands, and the glaciers that covered the area in the Ice Age carved out the current terrain with slow but constant movement and immense pressure.

Millar Channel is connected to watersheds such as the Flores Island Watershed, the Bedingfield Watershed, and the Sydney-Pretty Girl Watershed, of which details can be viewed here. The Flores Island Watershed consists of 15,000ha, though Millar Channel is likely only directly affected by half of it. This includes water bodies such as Grenville Lake, Steamer Creek, and Riley Creek. The land base of the Bedingfield Watershed is about 10,600ha and a good portion empties into Millar Channel proper, including Atleo River. The Sydney-Pretty Girl Watershed has a base of about 17,000ha, some of which empties into the part of Sydney Inlet that was considered along with Millar Channel in this analysis. Most of the shoreline of Sydney Inlet is protected, as is Obstruction Island of the Bedingfield Watershed, but this is comparatively little area. There are four fish farm sites near this section of Clayoquot Sound, all belonging to Cermaq, which has 10 fish farms in the Ahousat Territory overall. One in particular is right in Millar Channel, near sampling station 81, and another is in Dixon Bay a bit further away from station 75. There are also a few logging sites in this area, though it is not as heavily-impacted as other parts for Clayoquot Sound. One location is dense around the Atleo River, another is at Steamer bay on the North shore of Flores Island, and the last larger location is just off the intersection of Shelter Inlet and Sydney Inlet.

Data collection for Millar Channel was taken over the course of three days: station 63 on 13 Sep, stations 72, 73, 74, 75, 81, 39, and 33 on 14 Sep, and stations 32 and 31 on 15 Sep. Temperature did not changed drastically during these three days. Pressure was highest on 13 Sep and reached its lowest on 15 Sep. The maximum wind speed on 14 Sep was about 4km/h faster than the maximum on 13 or 15 Sep, though direction was fairly consistent through the sampling period. Tides were also similar on each day. It was mostly cloudy on 13 and 14 Sep with almost no precipitation, which progressed to cloudy on 15 Sep with 15mm precipitation.