Ecological Mitigation Measures

Shenzhen Western Corridor (SWC)

Objective of the Ecological Mitigation Measure:

To restore the hydrological function of gei wai at Mai Po by dredging of a water channel connecting the gei wai with the mudflat; and to restore inter-tidal mudflat by removal of exotic mangroves in the Mai Po Inner Deep Bay Ramsar Site.

Details:

Potential ecological impacts as a result of the SWC Project were considered not significant if mitigation measures are implemented. However, in view of the ecological sensitive nature of the Inner Deep Bay, the following additional enhancement measures were carried out to bring about a long-term beneficial effect to the Deep Bay ecosystem:

1. Deposited sediment in the water channel leading to gei wai Nos. 16 & 17 in the Mai Po Nature Reserve was dredged to one metre below the existing channel bottom prior to the commencement of construction of the Project to restore the water exchange regime at the silted up channel. The improvement work would increase the availability of prey to birds using the gei wai habitat and lead to a better water quality in the gei wais.

2. Exotic mangroves species and weed on the mudflat (such as Sonneratia sp. and Spartina sp.) within Inner Deep Bay were searched and removed to restore the decreasing area of inter-tidal mudflat available for bird feeding.

Results:

1. By recovering the level of the bottom of the water channel, the 24.3ha gei wai in Mai Po, which are key feeding ground of Black-faced Spoonbills, were restored. The effect of restoration is expected to last for over a decade.

2. Over 1,500 exotic mangrove trees were removed. The mudflat occupied by the exotic mangroves was restored.

Reference:

Ove Arup and Partners Ltd. (2003) Shenzhen Western Corridor – Investigation and Planning Environmental Impact Assessment Report. Report submitted to Highways Department, Hong Kong.

Photos:

Dredging of a water channel to restore the water exchange capacity in 2 gei wais at Mai Po.	Gei wai at Mai Po provides an important feeding and roosting site for waterbirds.
Mudflat habitat being occupied by fast growing exotic mangroves.	Removal of exotic mangrove tree at Mai Po to restore the mudflat habitat for waterbirds.