Since the plantings were completed in 2017, the drain has been subjected to several natural phenomena that has impeded the establishment of some of the plant materials – especially the aquatic plantings on the benched portions of the channel. Water levels in the Great Lakes have risen substantially since completion on the plantings in 2016. Furthermore, local wildlife such as ducks, geese and deer have been observed feeding within the drain. Consequently, many of the planted materials have either not taken hold, or have not survived. The poorest survival of plant materials has been experienced within the bench areas.

It is significant to note that the original drain improvement and landscaping design anticipated that grasses and other vegetation would continue to establish on the benched areas over time, when water levels were suitable (e.g. during periods of below average water levels). There should be sufficient plant material and seed stock in the existing ecosystem to induce natural propagation of a healthy plant community. Nevertheless, it should be anticipated that the inherent variability of water levels in the Great Lakes will continue to influence how the vegetation in the drainage corridor matures and evolves.

As long as Great Lake (and Detroit River) water levels remain at extreme high levels, establishment of grass hummocks will pose a challenge. Once levels retreat, these areas should be over-seeded with a suitable fescue seed mix to promote establishment of the grass hummock habitat.

10.4 Incidental Erosion

The north bank of the new channel has been treated with rock sheeting along its entire length to mitigate the potential for erosion and long-term bank recession. As noted, this measure was warranted given the proximity of the channel bank to a high-pressure gas main that runs parallel to the drain, and to a lesser extent to the proximity of the drain to the Perimeter Access Road.

In general, the south bank of the new channel has not been provided with any significant erosion protection, except for installation of short segments of stone berm at a few locations to address some local bank instability that developed after substantial completion of the works.

It is anticipated that some erosion of the south channel bank may occur over time. Minor erosion is not unusual along earth-lined channels. From Sta. 0+010 to 0+180, the south bank of the drain has been designed in anticipation that some minor erosion may occur. This decision was made in the interest of allowing sections of the south bank of the channel to function in a more natural state. In time, we anticipate that the south channel bank will colonize with native tree species, through the process of natural progression. Any minor erosion that occurs in conjunction with tree growth is considered acceptable.

10.5 Sedimentation of Habitat Features

Since completion of the channel improvements, some sedimentation of the rock vanes and other habitat features has been observed. The observed sedimentation is attributed to the combination of two factors, namely: