White Cart Water Flood Prevention Scheme

Contract 2 - environment

Protecting the wildlife of the White Cart Water - Issue 2

An update on ecological issues – summer / autumn 2009

Otters

A survey conducted before works commenced established the presence of otters (figure 1) all along the affected stretches of the White Cart Water. The movement of the otters and the presence of otter holts (dens) has been monitored by the project ecologist and signs of their continued movement up and down the river, past the flood protection works have been seen throughout the summer. These signs have included pawprints (figure 2) and spraint (faeces) (figure 3) on the riverbank adjacent to the works.

Figure 1 The European otter (Lutra lutra)

Figure 2 – Otter pawprints near to flood protection scheme construction works

Figure 3 – Otter spraint on a log adjacent to flood protection scheme construction works

In addition there have been several sightings of otter in or near the water. However, not all of these sightings have been confirmed and some observers may have confused the otters with mink which are also present along the river. One family of mink were resident in the old river wall very close to one of the work sections and the kits entertained the site workers on a daily basis with their play-fights outside the den (figure 4). Mink, however, are not a protected species. In fact they are classified as a pest and were introduced from North America. They have had a devastating effect on populations of our native species such as the water vole. They are not harmful to the much larger otters, however, and are likely to be killed by otters if challenged in otter territory.

Figure 4 – Mink kits playing outside the den

In compensation for the loss of good otter habitat and resting places as a result of the works, three artificial otter holts have been constructed at different places along the river and a fourth is planned for 2010. These holts have been constructed using breeze blocks to form a sleeping chamber and pipes to act as entrance tunnels (figure 5). The structures were then buried so that they are completely hidden from view.

Figure 5 – Excavation of hole and positioning of breeze blocks for artificial otter holt

During the day, otters spend most of the time sleeping and resting in their holts or hidden in dense vegetation. During the night however, when they are mostly active, they move through their territories either in the water or on paths along the riverbank. Much of the White Cart Water has steep walls along its length with no banks. In order to improve the riverbank habitat for the otter and facilitate its movements, otter ledges have been built at the foot of the new flood defence walls (figure 6).

Figure 6 – The mammal ledge at Cathcart.

Re-planting the riverbank

In order for the flood defence wall works to proceed, vegetation and trees have had to be cleared from the banks. Wherever possible, clearance was kept to a minimum and trees lying outside the footprint of the new flood wall were left and protected from damage by the construction machinery (figure 7).

Figure 7 – Original trees left in place adjacent to the new flood defence wall near Shawlands

Where clearance was essential, re-planting of the banks with trees and understory plants is now underway in those areas where works have been completed. Areas of riverbank on the “wet” side of the new flood defence wall are being planted with native species such as ash, willow and hawthorn which is in keeping with the nature of the White Cart Water as a wildlife corridor and haven (figure 8).

Figure 8 – Tree planting at Cathcart