There are two distinct topographical regions in the Cowichan Lake areaÃ³the mountainous areas and the lowland valleys.
Running through the length of Vancouver Island are the Insular Mountains. At 1345 metres, Heather Mountain is the highest peak north of Cowichan Lake while in the Seymour Range, south of the Lake, Townicut Mountain at 1260 metres is the highest point.
Two prominent valleys are within the area; the Cowichan and Nitinat. The Cowichan Valley was occupied by a valley glacier or ice tongue which moved eastward during the latter stages of glaciation. Kettles and kame topography are found in the middle and lower reaches of the Cowichan River. This river flows southeast for approximately 42 kilometers to Cowichan Bay. Cowichan Lake, at 163 metres above sea level, is one of Vancouver Island’s largest lakes.
Nitinat Lake is primarily fed by the Nitinat and Little Nitinat Rivers. These rivers are considerably shorter and smaller than the Cowichan, but the water volumes are almost as great. This is due to the very high precipitation during the winter. Nitinat Lake is salt water, which is a situation that occurs infrequently in nature. Nitinat Lake’s marine life is similar to other South Western Coastal Regions. At the Southwest end of the Lake there is a short narrow sandy ‘gap’ that separates the Lake from the Pacific Ocean. A dangerous tidal bore occurs in this area.
The Nanaimo Lowlands, (a raised portion of the Georgia Depression), extend inland as far as the Town of Lake Cowichan. The upper reaches of the Cowichan Valley are mantled with till as a result of the wasting of the last major ice age. This includes extensive sand and gravel beds up to 30 metres thick, as well as pockets of silt and clay. The Mountains on the north side of the lowlands rise gently away from the valley floor to about 800 metres (Hill 60 Range), while to the south, steeper slopes are encountered closer to the river rising to between 600 and 800 metres.