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A Showcase of Stream Restoration


Following the prompt action by relevant departments to stop the unauthorized works at the Tung Chung Stream in late 2003, an inter-departmental Task Force was set up to examine the reinstatement plan and to oversee the subsequent implementation of the reinstatement works. A Specialist Group, comprising members from the Advisory Council on the Environment and green/interest groups was convened by Environment, Transport and Works Bureau to discuss how the reinstatement works should be conducted from the ecological perspective.
Site inspection of the Specialist Group



The main objective of the reinstatement works was to restore the natural setting of the damaged section of the stream including the width, depth, topography, substrates and riparian habitats so as to promote natural recovery of the aquatic communities. The works involved removal of the access road, reinstatement of the longitudinal and cross-sectional profiles of the stream course, re-laying of boulders and pebbles on the stream course, creation of meanders, steps and pools along the stream course to provide a variety of habitats for aquatic fauna and replanting of vegetation along the stream bank to restore the riparian habitats. The reinstatement works commenced in mid-February 2004 and was completed in mid-April 2004.



After the completion of the reinstatement works, the Agriculture, Fisheries and Conservation Department (AFCD) initiated a two-year ecological monitoring programme to monitor the progress of ecological recovery of the stream. The monitoring programme covered physical characteristics, water quality, vegetation, aquatic macro-invertebrates and freshwater fishes of the stream. In order to provide reference data for the monitoring, an undisturbed natural section immediately upstream of the reinstated section has been selected as a reference site and samplings are carried out at both the reinstated section and the reference site.



At the end of the monitoring programme, the pools, riffles and boulders have been rearranged in a more natural setting by the force of water flow after heavy rainstorm. The numbers of species of freshwater fish and marco-invertebrates (e.g. larvae of mayflies and dragonflies) recorded are comparable to those recorded at the reference site. In particular, a fish species of conservation interest, Acrossocheilus beijiangensis (北江光唇魚), has returned to the reinstated section and continual sightings of this species imply that it has recolonized the reinstated stream section.

 Acrossocheilus beijiangensis (北江光唇魚)



Vegetation has also recolonized the damaged stream bank, which is now covered by grasses, shrubs and young trees. The monitoring results show the successful ecological recovery of the damaged section of the Tung Chung Stream, which could be used as a showcase for restoration of a tropical freshwater stream.

 Mayfly larva (蜉蝣)




The reinstated section of Tung Chung Stream, April 2006



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