the Detroit River as a result of the construction of a rock slope and jetty. A 16 m and 10 m reach of Broadway Drain will be lost as a result of the installation of the new culverts and the north side of the new channel will be kept free of woody vegetation to allow for access to the drain for maintenance purposes. Additional minor residual impacts will result from the temporary loss of riparian vegetation and overhead cover throughout the Broadway Drain. Additional losses of fish habitat will occur as a result of the works on Healy Drain and the drainage channel.
However, in order to account for any losses in fish habitat, offsetting measures will be implemented to re-construct and enhance fish habitats within the re-aligned Broadway Drain. While all reasonable efforts will be made to offset for impacts to fish habitat, minor residual effects may persist following construction while the channel stabilizes. Additional impacts may include the loss of naturalized sections of shoreline. Although landscaping and restoration is proposed for the new channel, the removal of trees, shrubs and other herbaceous plants currently found throughout the existing Broadway Drain will have a negative impact as it will take time for plantings and bank restoration efforts to become well established and begin contributing to fish habitat. To account for the minor residual impacts which may persist following construction, a Post Construction Monitoring Program will be initiated in order to document the post construction conditions and habitat usage, identify any deficiencies, and implement any contingency efforts to correct any major issues.
A series of tables have been created to demonstrate existing direct and indirect fish habitat that will be lost or impacted as a result of the proposed work. Existing habitat within the Broadway Drain is considered direct (seasonal) fish habitat and existing habitat within the Healy Drain and the drainage channel is considered indirect habitat. Offsetting measures will be achieved through the construction of new habitat within the realigned Broadway Drain, this new habitat has also been calculated.
Existing habitat lost in the Broadway Drain is shown in Table 4 and the proposed new habitat in the Broadway Drain is shown in Table 5. A description of habitat lost versus habitat created is compared in Table 6. Habitat that will be lost in the Detroit River is calculated using the footprint of the proposed rock jetty and the north bank rock slope, these are shown in Table 7 and Table 8. The indirect habitat lost in the Healy Drain and drainage channel has been calculated using estimates of area within the high water line and is shown in Table 9. The calculated areas of the impacted existing drain, new drain, and emergent portion of the new jetty are based on the maximum monthly mean water level of the Detroit River at this location.
To facilitate these calculations the following length and width measurements were used:
- Length of the existing Broadway Drain - 300m
- Average width of the existing Broadway Drain - 2.46m
- Length of the proposed Broadway Drain – 668m
- Average width of the proposed Broadway Drain - 9.5m
The 300m length of existing Broadway Drain refers to the upstream extent of inundation that would occur when the Detroit River is at its high water level. Similarly the 668m length of the proposed Broadway Drain would be entirely inundated during high water in the Detroit River, however this includes inundation of the culverts which exist along the Broadway Drain.
Table 4: Existing Habitat in Broadway Drain
TOTAL HABITAT AREA OFEXISTING DRAIN - UPSTREAM OFSANDIWCH STREET | TOTAL HABITAT AREA OF EXISTINGDRAIN - DOWNSTREAM OFSANDWICH STREET | TOTAL HABITAT AREA OFEXISTING DRAIN | TOTAL AREA OF WATER WITHINEXISTING DRAIN AT HWL OF DETROITRIVER |
---|---|---|---|
4,950 sq.m | 3,250 sq.m | 8,200 sq.m | 740 sq.m |