7 Ecological Impact

Agreement No. CE49/2002 (DS) Drainage Improvement in Southern Lantau Drainage Services Department Final EIA Report

7 ECOLOGICAL IMPACT

7.1 Introduction

7.1.1 The following section presents the results of an ecological assessment of potential impacts resulting from the Project. A literature review and field surveys were undertaken to establish ecological baseline conditions and the ecological importance of habitats/species potentially affected by proposed works was evaluated. The scale of possible ecological impacts resulting from the proposed works, including any cumulative impacts with concurrent major projects was assessed, and necessary mitigation measures were identified. Residual ecological impacts were assessed, and ecological monitoring and audit requirements identified.

7.2 Environmental Legislation, Standards and Guidelines

7.2.1 Guidelines, standards, documents and HKSAR Government ordinances and regulations listed in the following sections were referred to during the course of the ecological impact assessment. 7.2.2 The Country Parks Ordinance (Cap. 208) provides for the designation and management of country parks and special areas. Country parks are designated for the purpose of nature conservation, countryside recreation and outdoor education. Special Areas are created mainly for the purpose of nature conservation. 7.2.3 The Forests and Countryside Ordinance (Cap. 96) prohibits felling, cutting, burning or destroying of trees and growing plants in forests and plantations on Government land. Related subsidiary Regulations prohibit the selling or possession of listed restricted and protected plant species. The list of protected species in Hong Kong which comes under the Forestry Regulations was last amended on 11 June 1993 under the Forestry (Amendment) Regulation 1993 made under Section 3 of the Forests and Countryside Ordinance. 7.2.4 Under the Wild Animals Protection Ordinance (Cap. 170), designated wild animals are protected from being hunted, whilst their nests and eggs are protected from injury, destruction and removal. All birds and most mammals, including marine cetaceans, are protected under this Ordinance. The Second Schedule of the Ordinance which lists all the animals protected was last revised in June 1992. 7.2.5 The amended Town Planning Ordinance (Cap. 131) provides for the designation of Coastal Protection Areas, Sites of Special Scientific Interest (SSSIs), Conservation Area, Country Park, Green Belt or other specified uses that promote conservation or protection of the environment. The authority responsible for administering the Town Planning Ordinance is the Town Planning Board. 7.2.6 Chapter 10 of the HKPSG covers planning considerations relevant to conservation. This chapter details the principles of conservation, the conservation of natural landscape and habitats, historic buildings, archaeological sites and other antiquities. It also describes enforcement issues. The appendices list the legislation and administrative controls for conservation, other conservation related measures in Hong Kong and government departments involved in conservation.

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7.2.7 Annex 16 of the EIAO-TM sets out the general approach and methodology for assessment of ecological impacts arising from a project or proposal, to allow a complete and objective identification, prediction and evaluation of the potential ecological impacts. Annex 8 recommends the criteria that can be used for evaluating habitat and ecological impact. 7.2.8 EIAO Guidance Note No. 6/2002 clarifies the requirements of ecological assessments under the EIAO. 7.2.9 EIAO Guidance Note No. 7/2002 provides general guidelines for conducting ecological baseline surveys in order to fulfil requirements stipulated in the EIAO-TM. 7.2.10 The IUCN Red List of Threatened Species provides taxonomic, conservation status and distribution information on taxa that have been evaluated using the IUCN Red List Categories and Criteria. This system is designed to determine the relative risk of extinction, and the main purpose of the IUCN Red List is to catalogue and highlight those taxa that are facing a higher risk of global extinction. The IUCN Red List also includes information on taxa that are either close to meeting the threatened thresholds or that would be threatened were it not for an ongoing taxon-specific conservation programme.

7.3 Assessment Methodology

7.3.1 Existing literature documenting the ecology of the proposed works areas was reviewed. Relevant sources included:

• Chan, B.P.L. (2001) Sustainability and Biodiversity: the Impact, Alternative Design and Prospects for Restoration of Channelized Lowland Streams in Hong Kong: Unpublished Ph.D. thesis, University of Hong Kong • Gallacher, D. (2000) The Use of Benthic Macroinvertebrate Communities as Biomonitors of Hong Kong Streams. Unpublished Ph.D. Thesis. The University of Hong Kong, Hong Kong: 197pp. • Carey, G.J., Chalmers, M.L., Diskin, D.A., Kennerley, P.R., Leader, P.J., Leven, M.R., Lewthwaite, R.W., Melville, D.S., Turnbull, M., and Young, L. (2001): The Avifauna of Hong Kong. Hong Kong Bird Watching Society, Hong Kong. • Lau, M.W.N. & Dudgeon, D. (1999) Composition and distribution of Hong Kong amphibian fauna. Memoirs of Hong Kong Natural History Society 22:1-79. • Wilson, K.D.P. (1997) An annotated checklist of the Hong Kong dragonflies with recommendations for their conservation. Memoirs of the Hong Kong Natural History Society 21: 1-68. • Results of the HKU Biodiversity Survey • South Lantau and Mui Wo Development Feasibility Study (SLDF)

Ecological Surveys

7.3.2 To supplement existing data and fill identified data gaps, terrestrial ecology surveys covering both the wet and dry seasons were conducted from July 2003 to March 2004. The surveys covered an Assessment Area within 500m of the proposed works areas (Figure 7.1). The following ecological surveys were conducted to date in the Assessment Area:

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Habitat/vegetation surveys

7.3.3 Habitats inside the Assessment Area were identified and mapped. Plant species, relative abundance and growth forms were recorded. Surveys were conducted twice in the wet season and once in the dry season between September 2003 and March 2004. Identification of species and status in Hong Kong were made with reference to AFCD (2002), Siu (2000), Xing et al. (2000) and Wu & Lee (2000).

Avifauna Surveys

7.3.4 Avifaunal surveys of the Assessment Area were conducted on a monthly basis over 9 months, covering the wet and dry seasons. An additional night survey was conducted in March 2004. Species present and relative abundance of species was recorded.

Herpetofauna & Mammal Surveys

7.3.5 Herpetofauna/mammal surveys of the Assessment Area were conducted. Species presence and relative species abundance were recorded by direct observation, searching potential microhabitats, listening for calling animals, and searching for signs of animal activity (e.g., burrows, scats etc.). The herpetofauna/mammal surveys covered the wet (July & August 2003) and dry seasons (November 2003 and March 2004), and were conducted during the day and night.

Terrestrial Insect Surveys

7.3.6 Surveys of adult butterflies and odonates were conducted at the Assessment Areas in July 2003, November 2003, and March 2004. Species presence and relative species abundance were recorded by direct observation.

Freshwater Community Surveys

7.3.7 Surveys of fish populations in the affected rivers/streams were conducted between August 2003 and January 2004, covering the wet and dry seasons. Samples of each of the affected river section were undertaken by direct observation, bottle-trapping and hand nets. 7.3.8 Surveys of freshwater macroinvertebrate populations were conducted in August (wet season) and December 2003 (dry season). Samples were taken at two locations within each of the affected rivers using a standardised kick-sample with a D-shaped net (mesh size 500µm). The samples were preserved on site in 70% ethanol and were subsequently sorted in the laboratory. Identifications were to the highest feasible taxonomic level.

Impact Assessment

7.3.9 Potential ecological impacts arising from the Project were assessed following EIAO-TM Annex 16 guidelines and the impacts evaluated based on criteria in EIAO-TM Annex 8.

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7.4 Baseline Conditions

Sites of Conservation Interest

7.4.1 The location of recognised areas of conservation interest (as listed in EIAO-TM, Annex 16, Appendix A) within the Assessment Area are described in the following paragraphs.

Country Parks (CP)

7.4.2 Lantau South CP is situated approximately 300m to the west of the closest proposed works area at Luk Tei Tong (2) River. Natural areas of woodland exist within the Lantau South CP, principally on the lower slopes of Lantau and Sunset Peaks (both areas were designated as "Special Areas" in January 1980). Extensive afforestation work has been carried out in many places and plantations have been established mainly in Chi Ma Wan and around the water catchment areas of Shek Pik Reservoir. Scrub and coarse grassland cover much of Lantau Island, the latter being predominant on the higher areas exposed to strong winds. On the more sheltered lower slopes, and in stream valleys, the surface lends itself more to scrub growth. No direct or indirect impacts to Lantau South CP are anticipated to result from the proposed works.

Conservation Areas (CA)

7.4.3 Under the Mui Wo North Layout Plan – Lantau Island (Plan No. L/I-MWN/1, dated 1984), Butterfly Hill which lies to the north-west of Chung Hau Village, is zoned as a Conservation Area. Butterfly Hill comprises a small wooded knoll which supports secondary woodland habitat, along with occasional planted trees. The works area for the proposed Ling Tsui Tau U-Channel would fall partially within Butterfly Hill CA, although habitats affected by the works would be mostly limited to developed areas, with little impact to woodland habitats.

Habitat Type and Vegetation

Summary of Literature Review

7.4.4 The SLDF identifies twelve habitat types in the Mui Wo Area. Habitats of potential high ecological value identified in the Report include freshwater marsh habitat at Luk Tei Tong, secondary woodland habitats at Butterfly Hill and on the hillsides surrounding Mui Wo, and lowland streams in the Mui Wo Area. Summary of Current Surveys

7.4.5 Field surveys conducted for this Report identified thirteen habitat types within the Assessment Area, comprising: Rivers, Secondary Woodland, Active Dry Agriculture, Active Wet Agriculture, Inactive Dry Agriculture, Inactive Wet Agriculture, Shrubland, Fishponds, Plantation, Tree/Orchard, Bare Ground, Developed Land and Wasteland. A total of 358 plant species were recorded from these habitats (Appendix 7.3). A habitat map of the Assessment Area is given in Figure 7.1. Representative photographs of habitats are given in Appendix 7.1. Photographs of species of conservation interest are given in Appendix 7.2. A more detailed description of habitats recorded in the Assessment Area is given in the following sections.

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Rivers 7.4.6 The watercourses potentially affected by the proposed drainage improvement works comprise the lowland and estuarine reaches of three rivers and a small tributary of one of these rivers in Mui Wo Valley. At the downstream section of the proposed works areas, the rivers form an estuarine confluence to the north of the disused watchtowers. Limited mangrove formation has established along riparian habitats at the river confluence, with recorded species including Acanthus ilicifolius, Aegiceras corniculatum, Bruguiera gymnorrhiza and Kandelia candel. The upstream habitats of all three rivers are largely freshwater in nature, but consist of different habitat types, as described below.

Pak Ngan Heung (PNH) River 7.4.7 PNH River is relatively large stream with a mostly natural substrate. The riverbed of the lower section appeared to have been dredged with little in-stream complexity, but upstream reaches have a more natural riffle/pool formation. The riverbanks had been variously modified, with the middle section lined with gabion. Upstream reaches of the river have relatively natural riverbanks with extensive riparian vegetation. Water quality appeared to be good in general but the lower section of the river receives considerable raw household sewage.

Tai Tei Tong (TTT) River 7.4.8 TTT River is a large stream with mostly natural substrate. Although the middle section was lined with a concrete embankment, both the lower and upper sections have more natural pool/riffle formation.

Luk Tei Tong (LTT) River & Luk Tei Tong (2) River 7.4.9 LTT River is a relatively large stream flowing north through Mui Wo Valley. Much of the river has recently been subject to drainage improvement works, with banks lined with gabion and apparent extensive dredging works conducted. LTT (2) River is a small tributary of LTT River, which flows through Luk Tei Tong Marsh. The stream has extensive riparian vegetation formed largely from herbs and shrubs with occasional trees. Both LTT Rivers are affected by household sewage discharge, although water quality in general was reasonable.

Secondary Woodland 7.4.10 Secondary woodland habitats dominated the hillsides surrounding Mui Wo Valley, and also Butterfly Hill which lies in the north-east of the Assessment Area. Most areas of woodland were found to be structurally complex, with a semi-closed to closed canopy of approximately 10m to 14m. Sub-canopy growth was vigorous and well stratified with layers of trees, shrubs and herbaceous plant species, including native tree saplings. Human activities and disturbance within the woodland were generally minimal because of the steepness of the hill-slope and access difficulties. Plant communities in woodland areas were moderately diverse, with species encountered including the trees Alangium chinense, Bridelia tomentosa, Ficus hispida, Litsea glutinosa, Mallotus paniculata, Microcos paniculata, Schefflera octophylla and Zanthoxylum avicennae. The woodland habitats also supported numerous species of shrubs (e.g., Ardisia crenata, Daphniphyllum calycinum, Glochidion eriocarpum, Litsea rotundifolia, Psychotria rubra), herbs (e.g., Adiantum flabellulatum, Alocasia macrorrhiza, Blechnum orientale) and climbers (e.g., Celastrus hindsii, Dalbergia hancei, Desmos chinensis, Ficus pumila).

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7.4.11 Two plant species of conservation interest were recorded from secondary woodland habitats: the tree Aquilaria sinensis and the shrub Diospyros vaccinioides. Although common in Hong Kong, A.sinensis is endemic to China, where it is threatened by habitat loss. It is a Category III protected species under Chinese Legislation, and is listed as Vulnerable in the IUCN Red List of Threatened Species (IUCN, 2003). Diospyros vaccinioides is very common and widespread in Hong Kong. Despite its local abundance, this species is listed as critically endangered in the IUCN Red Data List (IUCN, 2003). 7.4.12 In addition to secondary woodland habitats recorded on valley hillsides and at Butterfly Hill, a smaller patch of open woodland habitat was recorded along the alignment of Tai Tei Tong River. This habitat appeared to have formed on recently abandoned agricultural land, and consisted of stands of trees interspersed with more open areas of grassland and shrubland. Species recorded from this habitat are generally common and widespread in Hong Kong (e.g., Ficus microcapra, Celtis tetrandra, Bridelia tomentosa, Acacia confusa), and no species of conservation interest were recorded from this area.

Active Agriculture (Dry & Wet) 7.4.13 Scattered areas of (mostly dry) actively farmed agricultural land were recorded throughout the Assessment Area. Species and structural diversity in these habitats was low, being dominated by crop plants (including Brassica chinensis, Brassica alboglabra, Musa paradisiaca, and Saccharum officinarum), along with grasses and common weeds (e.g., Digitaria ciliaris, Wedelia chinensis, Hypericum japonicum, Miscanthus sinensis, Panicum repens, Mikania micrantha, Amaranthus viridis).

Inactive Agriculture (Dry & Wet) 7.4.14 Large areas of Mui Wo valley were found to be dominated by (largely wet) inactive agricultural land. Species diversity in wet inactive agricultural land was moderate, with vegetation dominated by grasses, sedges and other herbs, some of which are commonly recorded from wetland habitats (e.g., Amaranthus viridis, Apluda mutica, Colocasia esculenta, Cyclosorus interruptus, Digitaria ciliaris, Eclipta prostrata, Fuinera umbellate, Hypericum japonicum, Ipomoea aquatica, Paspalum distichum). No plant species of conservation interest were recorded from this habitat type. 7.4.15 Most of the inactive wet agricultural land within the Assessment Area was moderately fragmented, being interspersed amongst areas of active agricultural land, villages, orchards and other habitat types. The largest area of inactive wet agricultural land was recorded to the northeast of Luk Tei Tong Village. This area of habitat forms a large expanse of wetland habitat (referred to hereafter as Luk Tei Tong Marsh), as shown in Figure 7.1. Wetland habitats within the marsh did show some degree of heterogeneity, with areas directly to the north of Luk Tei Tong Village found to be drier, have less established wetland vegetation and be generally subject to higher levels of disturbance than areas to the north-east and north-west of the village. The area within and adjacent to the proposed LTT (2) River Bypass Channel alignment in particular was found to be mostly dry, with vegetation along much of the alignment dominated by the common and exotic weed species Mikania micrantha.

Shrubland 7.4.16 Small patches of shrubland 1m-2m in height were recorded around the peak of Butterfly Hill and close to Pak Ngan Heung Village. Vegetation recorded from this habitat type was similar to adjacent areas of woodland, and included common tree (e.g., Cratoxylum cochinchinense,

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Ficus hispida, Litsea glutinosa, Mallotus paniculata) shrub (e.g., Glochidion eriocarpum, Litsea rotundifolia, Rhaphiolepis indica, Rhodomyrtus tomentosa) herb (e.g., Cymbopogon spp. Echinochloa crusgalli, Liriope spicata) and climber (e.g., Bauhinia championii, Celastrus hindsii, Millettia nitida) species. 7.4.17 One plant species of conservation interest, the shrub Diospyros vaccinioides, was recorded from this habitat type. Diospyros vaccinioides is very common and widespread in Hong Kong. Despite its local abundance, this species is listed as critically endangered in the IUCN Red Data List (IUCN, 2003).

Fishponds 7.4.18 Several abandoned fishponds were recorded in the Assessment Area to the south of the disused watchtowers. These ponds were relatively disturbed, with evidence of recent dumping of waste (e.g., tyres) observed. Vegetative cover within these ponds was largely limited to isolated trees (e.g., Sapium sebiferum, Leucaena leucocephala) grasses (e.g., Imperata cylindrica, Miscanthus sinensis) and other vegetation growing along the pond bunds. In other areas, wetland and aquatic species (e.g., Cyclosorus interruptus, Elecocharis dulcis, Equisetum debile, Fuinera umbellate, Hypericum japonicum, Ludwigia spp., Phragmites spp.) covered virtually the whole of the pond surface. Ponds close to the disused watchtowers were subject to saltwater intrusion, and supported some mangrove and mangrove associated species (e.g., Acanthus ilicifolius, Bruguiera gymnorrhiza, Kandelia candel, Acrostichum aureum, Avicennia marina).

Plantation & Tree/Orchard 7.4.19 Plantation habitats were largely limited to roadside areas and slopes close to the South Lantau Road, in the South east of the Assessment Area. Abundant species recorded from this habitat type included exotic trees commonly planted in Hong Kong (e.g., Acacia maginum, Acacia confusa). Common native pioneer tree species (e.g., Mallotus paniculatus, Celtis tetradra, Sapium sebiferum and Litsea glutinosa) were also established in the sub-canopy of this habitat. 7.4.20 Patches of orchard and tree plantings were scattered throughout Mui Wo. This habitat type was dominated by fruiting tree species such as Dimocarpus longan, Syzygium jambos, Citrus sp., Clausena lansium and Litchi chinensis. This habitat type was generally limited to small and fragmented patches, and was poor in species diversity because of management practices such as the clearance of under-storey weeds and the application of pesticide. 7.4.21 No plant species of conservation interest were recorded from plantation or tree/orchard habitats.

Developed Land, Bare Ground & Wasteland 7.4.22 Areas of highly disturbed habitat found within the Assessment Area included developed land (including Mui Wo Town and surrounding villages) recently cleared bare ground and wasteland (habitats formed as a result of intensive human activities and either wholly or partly covered by weedy or ephemeral vegetation). These habitats were considered to be of little ecological interest.

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Fauna

7.4.23 Fauna recorded in the Assessment Area during field surveys are listed in Appendix 7.4. Summaries of previous records of fauna recorded in Mui Wo area, together with fauna recorded during surveys conducted for this Report are given in the following sections. Avifauna

Summary of Literature Review

7.4.24 The results of the 1993-1995 Breeding Bird Survey conducted by the Hong Kong Bird Watching Society (HKBWS) are presented in Carey et al. (2001). The two 1km squares listed in the Mui Wo Area that cover much of the current Assessment Area were found to support a total of 46 breeding bird species, with both of these squares considered to support a high diversity of breeding birds. Mui Wo appears fairly typical of many areas supporting high numbers of breeding birds, which Carey et al. (2001) describe as ‘low-lying coastal areas backed by shrub and woodland, followed by inland valleys that remain relatively undeveloped with mixtures of agricultural land and woodland edge’. Despite relatively high species richness, the Mui Wo Area is not included amongst the 22 sites of ornithological importance to breeding bird species in Hong Kong that are recommended for protection by Carey et al. (2001), with most of the recorded species being common and widespread in Hong Kong. 7.4.25 In addition to the results of the Breeding Bird Survey, there are records of a number of avifaunal species of conservation interest from Mui Wo reported in Carey et al. (2001). These species are listed in Table 7.1 below. Although some records are relatively old, and others refer to occasional sightings of birds, it is noteworthy that all species of conservation interest recorded from the area are wetland dependent to a greater or lesser extent; suggesting that Luk Tei Tong Marsh and other wetlands in the Mui Wo Area has provided an important foraging habitat for wetland avifaunal species. Only three of the species listed in Table 7.1 (Striated Heron, Slaty-breasted Rail and White-shouldered Starling) are known or suspected to have bred in the Mui Wo area, suggesting that wetland habitats in the Area do not form a key breeding habitat for wetland dependent avifauna.

Table 7.1 – Avifaunal Species of Conservation Interest Previously Recorded From the Mui Wo Area*

Common Name Species Name Conservation Status** Chinese Pond Heron Ardeola bacchus PRC (RC) Striated Heron Butorides striatus (LC) Great Egret Egretta alba PRC (RC) Little Egret Egretta garzetta PRC (RC) Cinnamon Bittern Ixobrychus cinnamomeus LC Black Bittern Ixobrychus flavicollis LC Yellow Bittern Ixobrychus sinensis (LC) Night Heron Nycticorax nycticorax (LC) Falcated Duck Anas falcate RC Brown Crake Amaurornis akool LC Watercock Gallicrex cinerea RC Water Rail Rallus aquaticus LC

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Common Name Species Name Conservation Status** Slaty-breasted Rail Gallirallus striatus RC Greater-painted Snipe Rostratula benghalensis LC Eastern Curlew Numenius madagascariensis LC Chinese Penduline Tit Remiz consobrinus RC White-shouldered Starling Sturnus sinensis (LC) Purple-backed Starling Sturnus sturninus LC Common Starling Sturnus vulgaris LC * Source – Carey et al (2001) ** LC – Local Concern (Habitat loss/damage in Hong Kong would pose significant threat to local survival); PRC – Potential Regional Concern (Large, secure populations in Hong Kong are of regional significance); RC – Regional Concern (Habitat loss/damage in Hong Kong would pose significant threat to regional survival); PGC – Potential Global Concern (Large, secure populations in Hong Kong are of global significance); GC – Global Concern (Habitat loss/damage in Hong Kong would pose significant threat to global survival). Refer to Fellowes et al. (2002) for further explanation of status. Summary of Current Surveys

7.4.26 A total of 81 avifaunal species were recorded during surveys of the Assessment Area, with commonly encountered species including Spotted Dove (Streptopelia chinensis), Yellow-bellied Prinia (Prinia flaviventris), Common Tailorbird (Orthotomus sutorius), Crested Bulbul (Pycnonotus jocosus) and Crested Myna (Acridotheres cristatellus). 7.4.27 In total, 16 avifaunal species of conservation interest were recorded from the Assessment Area during recent surveys, 11 of which are wetland dependant. These species are listed in Table 7.3b, and described in the following paragraphs.

Ardeids 7.4.28 Seven ardeid species of conservation interest (Grey Heron, Ardea cinerea; Great Egret, Casmerodius alba; Little Egret, Egretta garzetta; Cattle Egret, Bubulcus ibis; Chinese Pond Heron, Ardeola bacchus; Striated Heron, Butorides striatus and Black-crowned Night Heron, Nycticorax nycticorax) were recorded in the Assessment Area. The large, fairly secure populations of Great Egret, Little Egret and Grey Heron that occur in Hong Kong are considered important in a regional context (Fellowes et al., 2002). Chinese Pond Heron are considered of conservation importance due to locally declining populations. Despite the reduced numbers of this species in Hong Kong, the local population is still large enough to be of regional significance (Carey et al., 2001). Cattle Egret, Striated Heron and Black-crowned Night Heron are all considered of local conservation interest due to the limited number of sites in Hong Kong where these species are known to breed (Fellowes et al., 2002). 7.4.29 Ardeid species were observed utilising various habitats within the Assessment Area, with the highest densities recorded in the estuarine confluence of the three rivers close to the disused watchtower, and the lower reaches of PNH and LTT Rivers (Figure 7.1 refers). No egretry or ardeid breeding was observed in the Assessment Area during field surveys.

Raptors 7.4.30 Records of single Black Kites (Milvus migrans) soaring over the Assessment Area were made in July and December 2003. Black Kites are abundant winter visitors and residents in Hong Kong, where they are recorded from widespread areas and numerous habitat types, including urbanised areas. This species is considered of regional conservation concern by Fellowes et al., (2002) due to the small but relatively secure breeding population occurring in Hong Kong, and the limited number of known roosting and nesting sites in Hong Kong.

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Ducks 7.4.31 A single Common Teal (Anas crecca) was recorded from LTT River in October 2003. Common Teals are abundant winter visitors to Hong Kong, with annual records of several thousand birds from the Deep Bay Area. The large wintering population of this species is considered of regional conservation concern by Fellowes et al. (2002).

Kingfishers 7.4.32 Observations of one or two White-throated Kingfisher (Halcyon smyrnensis) were made in most months during the field surveys. Most records were from freshwater/estuarine river sections. White-throated Kingfishers are a relatively common resident species in Hong Kong, but are considered of local conservation concern by Fellowes et al. (2002) due to the restricted number of breeding sites of this species.

Other Birds 7.4.33 Two Pacific Swifts (Apus pacificus) were recorded flying over the Assessment Area in March 2004. This species is a generally a passage migrant in Hong Kong, but breeding has probably occurred on one or two offshore islands (Carey et al., 2001). The species is considered of local conservation concern by Fellowes et al. (2002) due to the restricted number of known suspected breeding sites in Hong Kong. Mui Wo does not provide a suitable breeding area for the species, and it is likely the sighting over the Assessment Area was of passage migrants only. 7.4.34 A pair of Zitting Cisticola (Cisticola juncidis) was recorded from Luk Tei Tong Marsh in January 2004. This species is a relatively common winter visitor and passage migrant to Hong Kong, with a small breeding population restricted to the Northern New Territories (Carey et al., 2001). The species is widespread in open areas of long grass, but is most abundant at such places as Long Valley and areas of fishponds/filled fishponds (ibid). Fellowes et al. (2002) consider the species of local conservation concern, given its restricted local distribution. 7.4.35 One observation was made of a Plumbeous Redstart (Rhyacornis fulignosus) in PNH River in February 2004. This species occurs in Hong Kong as a scarce winter visitor (Carey et al 2001) and is listed by Fellowes et al (2002) as of local conservation concern. 7.4.36 A small flock of Yellow-breasted Bunting (Emberiza aureola) were recorded from a small patch of wasteland within Luk Tei Tong Marsh in October 2003. Yellow-breasted Buntings are passage migrants in Hong Kong, with small numbers over-wintering. They are generally restricted to areas of open country, including wet and dry farmland, grassland in abandoned agricultural areas and landfill sites, and the edges of reedbeds (Carey et al., 2001). Numbers of this species in Hong Kong have undergone a marked decline in recent years, most probably as a result of the extensive trapping of this species in Mainland China, where it is considered a food delicacy (ibid.). Fellowes et al. (2002) consider the species of regional conservation concern due to its restricted distribution in Hong Kong, and local, regional and global population decline. 7.4.37 A single Yellow-billed Grosbeak (Eophona migratoria) was recorded flying over the Assessment Area in September 2003. This species is a scarce and localised winter visitor to Hong Kong, with small flocks generally recorded from favoured habitats such as orchards, fung shui woodland and woodland fragments close to agricultural land (Carey et al. 2001).

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Records of this species in Hong Kong have been declining through the 1990’s. The decline is thought to result from the over-collection of wild birds outside of Hong Kong for sale as pets (ibid). The species is considered of local conservation concern by Fellowes et al. (2002) because of its restricted distribution in Hong Kong and declining numbers. 7.4.38 White-shouldered Starling (Sturnus sinensis) is considered of conservation concern in Hong Kong on the basis of a small and declining breeding population. The Mui Wo area previously supported the largest known breeding population in Hong Kong, with 15 pairs recorded nesting in the disused watchtowers (Carey et al. 2001). At least one pair is known to have bred in the town at Mui Wo during summer 2003, although none were observed using the watchtowers during surveys conducted for this Report in 2003. An additional site visit conducted in June 2004 recorded one pair breeding in the watchtowers. Other records obtained during the surveys were of one flying over Mui Wo town in July 2003 (probably a breeding bird) and a flock of nine at Tai Tei Tong village in August 2003, which may have been either local birds or a migrating flock.

Herpetofauna & Mammals

Summary of Literature Review

7.4.39 Herpetofaunal and mammal species have been recorded from the Mui Wo area during previous surveys (e.g., Lau & Dudgeon, 1999, Biodiversity Survey). Although the majority of mammal and herpetofauna records are of common and widespread species (e.g., rodents and common frogs and toads), three herpetofaunal species of conservation interest have been recorded in the Mui Wo Area; Chinese Bullfrog (Rana rugulosa), Romer’s Tree Frog (Philantus romeri) and Chinese Cobra (Naja atra). 7.4.40 Chinese Bullfrog have been recorded from agricultural land at both Pak Ngan Heung and Mui Wo (Lau & Dudgeon, 1999, Biodiversity Survey). This species is locally uncommon with declining local, regional and global populations and is considered of potential regional conservation concern (Fellowes et al. 2002). The declining populations of this species are thought to result from habitat loss, over-collection for human consumption and the widespread use of pesticides (Karsen et al., 1998). 7.4.41 Romer’s Tree Frog (RTF) have been reported from Pak Ngan Heung, Tai Tei Tong, Mui Wo, and woodland habitats close to Luk Tei Tong and at Butterfly Hill (Lau & Dudgeon, 1999; Biodiversity Survey; Dudgeon & Chan, 1996). RTF is locally common on Lantau and Lamma Islands, and records have also been made from Po Toi Island and Chek Lap Kok (Karsen et al., 1998). The construction of the international airport at Chek Lap Kok posed a severe threat to the RTF population on the Island. A captive breeding programme was therefore established using individuals from Chek Lap Kok, with successfully reared individuals released to various parts of the New Territories and Hong Kong Island (ibid). Despite its local abundance on Lantau, RTF would appear to be a Hong Kong endemic, and is therefore considered a species of potential global conservation concern by Fellowes et al. (2002). 7.4.42 A record of a Chinese Cobra was made from Luk Tei Tong Marsh during the Biodiversity Survey. The Cobra is a relatively common and widespread species in Hong Kong, found in a variety of habitat types (Karsen et al., 1998). Fellowes et al. (2002) consider the relatively large and secure population of this species that occurs in Hong Kong of potential regional conservation concern due to declines in regional and global populations of the Cobra.

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Summary of Current Surveys

7.4.43 Six species of amphibian, three species of reptile and no mammals were recorded from the Assessment Area during recent surveys. The majority of species observed are common and widespread in Hong Kong. Only one of the previously recorded species of conservation interest (Chinese Bullfrog) was recorded from the Assessment Area. A single Bullfrog was observed in a small pond within the Luk Tei Tong Marsh area in August 2003. This pond was found to be dry on a subsequent visit in December 2003, but it is possible that Chinese Bullfrog also occur in other areas of the Marsh. 7.4.44 No records of RTF were made during the recent surveys, but it should be noted that the species is often difficult to detect in the field due to its small size and cryptic nature. Dudgeon & Lau (1999) have noted that annual monitoring at some sites where RTF had been released following the captive breeding programme failed to detect any animals in some years, even though visits in subsequent years revealed their continued presence. It is therefore likely that RTF still occurs in suitable woodland habitats around the Mui Wo Area.

Terrestrial Invertebrates

Summary of Literature Review

7.4.45 Wilson (1997) and Wilson et al. (2004) provide a record of some dragonfly species from the Mui Wo Area. Two relatively uncommon species: Blue Sprite (Pseudagrion microcephalum) and Sapphire Flutterer (Rhyothemis triangularis) have previously been recorded from Luk Tei Tong marsh. Both species are considered of local conservation concern by Fellowes et al. (2002) due to restricted local populations. However, Wilson et al. (2004) consider the Sapphire Flutterer to be more common than previously thought. An additional odonate of conservation interest, Gynacantha japonica, was reported from Butterfly Hill during the Biodiversity Survey. This species is also listed as being of local conservation concern by Fellowes et al. (2002), due to a restricted local occurrence.

Summary of Current Surveys

7.4.46 During the field surveys, 24 species of dragonfly were recorded in the Assessment Area. None of the species recorded are considered rare in Hong Kong (Wilson et al, 2004), or are listed as species of conservation concern by Fellowes et al. (2002). Species recorded included two marsh specialists (Pied Percher, Neurothemis tullia tullia and Marsh Skimmer, Orthetrum luzonicum) and four species found only at relatively unpolluted streams (Chinese Greenwing, Neurobasis chinensis chinensis; Common Blue Jewel, Rhinocypha perforata perforata; Black-banded Gossamerwing, Euphaea decorata and Black Threadtail, Prodasineura autumnalis). The uncommon Blue Sprite (Pseudagrion microcephalum) has previously been recorded in Luk Tei Tong marsh. Although not recorded during the recent surveys, it is possible this species still occur in the Assessment Area. 7.4.47 Thirty-one butterfly species were recorded from the Assessment Area. With the exception of the locally uncommon Bush Hopper (Ampittia dioscorides) and Grass Demon (Udaspes folus), all butterfly species observed are considered common or very common in Hong Kong (Young & Yiu, 2002). None of the recorded species are considered of conservation interest by Fellowes et al. (2002).

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Freshwater Fish

Summary of Literature Review

7.4.48 Chong & Dudgeon (1992) included streams in Mui Wo as part of a territory wide survey of freshwater fish. No species of conservation interest were reported from the Mui Wo Area. Summary of Current Surveys

7.4.49 During field surveys conducted for this Report, 19 species of fishes were recorded from the Assessment Area. Sixteen species were recorded from both PNH and TTT Rivers, and 11 species from LTT & LTT (2) Rivers. In addition to these species, local residents noted the presence of Paradise Fish (Macropodus opercularis) in the Assessment Area. Most of the recorded species are relatively common in Hong Kong, and the fish fauna was dominated by brackish-water species. The lower, estuarine reaches of the rivers appear to be a nursery and breeding ground for some of these species (e.g. Mugil cephalus and Lutjanus argentimaculatus). 7.4.50 Two fish species of conservation interest were recorded from the Assessment Area during the surveys; Flagtail (Kuhlia marginata) and Predaceous Chub (Parazacco spilurus). A single K. marginata was observed from the rocky upper reaches of PNH River. This species was only recently discovered in Hong Kong and is known locally from just two other river/stream sites. Kuhlia marginata is endangered in Hong Kong due to habitat loss, and is considered of regional conservation concern by Fellowes et al. (2002). Parazacco spilurus was common in pools along the upper reaches in PNH and TTT Rivers. Parazacco spilurus is common and widespread in Hong Kong, but is classified as Vulnerable in the China Red Data Book (Yue and Chen, 1998) because of its scientific value and restricted global range.

Freshwater Invertebrates

Summary of Literature Review

7.4.51 Gallacher (2000) provides data on freshwater invertebrates recorded from Pak Ngan Heung River. In general, the community was found to be numerically dominated by Chironomid larvae and Baetis sp. nymphs. The presence of estuarine crabs (Eriocheir sp.) and polychaete worms suggested the river was tidally influenced. Summary of Current Surveys

7.4.52 A salinity gradient was present in all of the sampled rivers, with estuarine species such as crabs (e.g., Hemigrapsus penicillatus and Varuna litterata) and polychaete worms being the most abundant taxa at the downstream sampling locations, while freshwater insects such as Ephemeroptera, Anisoptera, Trichoptera, Coleoptera and Diptera tended to be more abundant in the upstream sampling locations of all streams. LTT (2) River had the richest aquatic insect community, with 15 taxa in 5 insect Orders identified at the upstream sampling location (as compared with 12 taxa at TTT River and 11 at PNH River). The lack of pollution intolerant taxa (e.g., stoneflies, heptageniid mayflies) at the freshwater, upstream sections may reflect the moderate inputs of domestic sewage and agricultural run-off received by the Rivers.

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7.5 Ecological Value

7.5.1 In accordance with the EIAO-TM Annex 8 criteria, the ecological importance of recorded habitats has been evaluated in Tables 7.2a-7.2e below. Table 7.2a Ecological Value of River Habitats in the Assessment Area.

Criteria Rivers Naturalness Although they remain largely natural, river habitats in the Assessment Area have been variously modified, and receive moderate inputs of domestic sewage and agricultural run-off. Size PNH, TTT and LTT Rivers: Moderate. LTT (2) River: Small (approximately 1-2m in width). Diversity Moderately diverse fish communities. Rarity The estuarine confluence and lower reaches of the rivers supported several avifaunal species of conservation interest, comprising: Grey Heron (Ardea cinerea), Great Egret (Casmerodius alba), Little Egret (Egretta garzetta), Chinese Pond Heron (Ardeola bacchus), Striated Heron (Butorides striatus), Black-crowned Night Heron (Nycticorax nycticorax) and White-throated Kingfisher (Halcyon smyrnensis).

PNH River: Supported fish species of conservation interest: Flagtail (Kuhlia marginata) & Predaceous Chub (Parazacco spilurus). One avifaunal species of conservation interest recorded: Plumbeous Redstart (Rhyacornis fulignosus).

TTT River: Supported fish species of conservation interest: Predaceous Chub (Parazacco spilurus).

LTT & LTT (2) Rivers: Supported the avifaunal species of conservation interest recorded: Common Teal (Anas crecca)

Relatively unmodified lowland rivers are becoming increasingly rare habitats in Hong Kong. Recreatability Moderate. Fragmentation The habitats are generally unfragmented, although agricultural weirs (such as in PNH River) could prevent the migration of fish between downstream and upstream reaches of the rivers. Ecological linkage The rivers (especially LTT & LTT (2)) are structurally and functionally linked to areas of marshland in the Assessment Area. PNH River flows close to woodland at Butterfly Hill, and is functionally linked to this habitat. Potential value With the removal of pollution sources and restoration of river-beds and banks, the ecological value of all rivers could be improved. Nursery ground The lower, estuarine reaches of the rivers appear to serve as a nursery and breeding ground for some common brackish fish species. Age N/a Abundance/Richne Moderate. ss of Wildlife Ecological value PNH River: Moderate-high TTT River: Moderate LTT River: Moderate LTT (2) River: Low-Moderate

Table 7.2b Ecological Value of Woodland and Active Agriculture (Dry & Wet) Habitats in the Assessment Area.

Criteria Woodland Active Agriculture (Dry & Wet) Naturalness Habitat is largely natural, although secondary in Habitats are man-made. nature. Size Habitat covers large areas of hillside surrounding Habitats are small in size. Mui Wo Valley. Diversity Secondary Woodland: Moderate. Low. Open Woodland: Low-moderate.

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Criteria Woodland Active Agriculture (Dry & Wet) Rarity Two plant species of conservation interest, Single records of Chinese Pond Heron Aquilaria sinensis and Diospyros vacciniodes (Ardeola bacchus) and White-throated recorded from secondary woodland. Kingfisher (Halcyon smyrnensis) from active dry agricultural land. One Little Egret (Egretta garzetta) recorded from open woodland habitat adjacent to TTT River.

Previous records of Romer’s Tree Frog ( Philautus romeri) from woodland areas in Mui Wo. Re-creatability Moderate, although the habitat would take several Habitat readily created on suitable areas of decades to mature. low-lying land. Fragmentation The habitat is largely unfragmented. Moderate-high. Ecological linkage Falls partially within Conservation Area and The habitats are adjacent to areas woodland, Country Park. marsh and streams/rivers of conservation interest. Woodland habitat is linked with streams and adjacent areas of marsh. Potential value Moderate. Low-moderate. Nursery ground Woodland habitats provide potential breeding No significant records. habitat for Romer’s Tree Frog. Age Woodland is several decades old. N/a Abundance/Richness Secondary Woodland: Moderate. Low. of Wildlife Open Woodland: Low-moderate. Ecological value Secondary Woodland: Moderate-High. Low. Open Woodland: Low-moderate.

Table 7.2c Ecological Value of Inactive Agriculture (Dry & Wet) and Shrubland Habitats in the Assessment Area

Criteria Inactive Agriculture (Dry & Wet) Shrubland Naturalness Habitats are man-made, though have been Habitat largely natural, although secondary in abandoned for a number of years. nature. Size Inactive wet agricultural land covers a large area Small. of Mui Wo Valley. Diversity Low-Moderate. Moderate-high. Rarity Several avifaunal species of conservation interest One plant species of conservation interest, recorded within and adjacent to inactive wet Diospyros vacciniodes, recorded from this agricultural land at Luk Tei Tong Marsh, habitat type. comprising: Cattle Egret (Bubulcus ibis), Chinese Pond Heron (Ardeola bacchus), White-throated Kingfisher (Halcyon smyrnensis), Zitting Cisticola (Cisticola juncidis) and Yellow-breasted Bunting (Emberiza aureola).

Chinese Bullfrog (Rana rugulosa) recorded from small pond within the Luk Tei Tong Marsh area.

Previous records of avifauna, herpetofauna dragonfly species of conservation interest from Luk Tei Tong Marsh.

Freshwater marshes are relatively rare habitats in Hong Kong. Re-creatability Habitat readily created on suitable areas of Moderate, although the habitat would take low-lying land. several years to mature. Fragmentation Large area of inactive wet agricultural land at Luk Habitat limited to small isolated patches, Tei Tong Marsh is unfragmented, although marsh although these areas are mostly contiguous habitat within this area is relatively patchy with adjacent woodland habitats.

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Criteria Inactive Agriculture (Dry & Wet) Shrubland Ecological linkage The habitats are structurally and functionally Shrubland habitat at Butterfly Hill falls within linked to areas woodland and streams/rivers of a Conservation Area, and is structurally and conservation interest. functionally linked to adjacent areas of woodland. Potential value Low-moderate. Moderate. Nursery ground The habitat forms a potential breeding ground for No significant records. some avifaunal, herpetofaunal and dragonfly species of conservation interest. Age N/a. Habitat is probably over 10 years in age. Abundance/Richness Luk Tei Tong Marsh: Moderate. Low-moderate. of Wildlife Other Inactive Agriculture: Low-moderate. Ecological value Luk Tei Tong Marsh: Moderate-High Low-moderate. Other Inactive Agriculture: Low-moderate.

Table 7.2d Ecological Value of Fishpond and Plantation & Tree/Orchard Habitats in the Assessment Area

Criteria Fishponds Plantation & Tree/Orchard Naturalness Habitats man-made, although apparently Habitats man-made. abandoned for several years. Size Small. Small. Diversity Low-moderate. Low-moderate. Rarity Chinese Pond Heron (Ardeola bacchus) and Cattle Single record of Chinese Pond Heron (Ardeola Egret (Bubulcus ibis) recorded from this habitat bacchus) recorded from this habitat type. type. Re-creatability Habitat can be easily re-created on suitable areas of High, although habitat would take several years low-lying land. to mature. Fragmentation Low. Moderate-high. Ecological linkage Fishponds are structurally and functionally linked The habitats are not structurally or functionally with adjacent areas of marsh. Tidally influenced linked to any recognised area of conservation ponds are linked to streams/rivers. interest. Potential value Moderate. Low-moderate. Nursery ground No significant records. No significant records. Age N/a Habitats appear over 10 years old. Abundance/Richne Low-moderate. Low. ss of Wildlife Ecological value Low-Moderate. Low.

Table 7.2e Ecological Value of Developed Land, Bare Ground & Wasteland Habitats in the Assessment Area

Criteria Developed Land, Bare Ground & Wasteland Naturalness Man-made habitats. Size Moderate. Diversity Low. Rarity White-shouldered Starling (Sturnus sinensis) recorded from Tai Tei Tong Village, and recorded breeding in Disused Watchtowers. Re-creatability High. Fragmentation Moderate. Ecological linkage No significant linkage. Potential value Low. Nursery ground White-shouldered Starling (Sturnus sinensis) recorded breeding in Disused Watchtowers. Age N/a Abundance/Richne Low. ss of Wildlife Ecological value Very Low.

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7.5.2 Aside from the small LTT (2) River (rated low-moderate ecological value), the rivers surveyed in the Assessment Area are considered of moderate or moderate-high ecological value. These relatively unmodified lowland streams were found to support moderately diverse fish communities, including some species of conservation interest. The estuarine and lower reaches of the Rivers also provided foraging resources for avifauna, including several species of conservation interest. 7.5.3 Secondary woodland habitats on the hillsides surrounding Mui Wo Valley and on Butterfly Hill were largely unfragmented, relatively mature, and supported moderately diverse plant communities, including some species of conservation interest. Furthermore, these woodland areas provide a potential breeding habitat for RTF. Overall, these habitats were considered of moderate-high ecological value. Open woodland habitat close to TTT River was apparently formed more recently on abandoned agricultural land, had low-moderate plant diversity, and supported no plant species of conservation interest. This habitat was considered of low-moderate ecological value. 7.5.4 Both dry and wet active agricultural land was considered of low ecological value. These habitats had low plant diversity; being dominated by crop plants, weeds and grasses, and supported no plant species of conservation interest. 7.5.5 Much of the inactive agricultural land (dry & wet) in the Assessment Area was considered of low-moderate ecological value only, supporting a moderate diversity of plants, but no species of conservation interest. Luk Tei Tong Marsh comprises a large, unfragmented expanse of inactive agricultural land was considered of higher ecological value, with several wildlife species of conservation interest recorded from this habitat (although these species occurred in low numbers). Previously, several avifaunal, herpetofaunal and dragonfly species of conservation interest have also been recorded from the marsh, and it is possible these species still utilise the marsh habitat. Overall, Luk Tei Tong Marsh was rated as being of moderate-high ecological value, although as noted in Section 7.4.15, wetland habitats within the marsh did show some degree of heterogeneity. Areas directly to the north of Luk Tei Tong Village were found to be drier, have less established wetland vegetation and be generally subject to higher levels of disturbance than areas to the north-east and north-west of the village. The more disturbed areas of the Marsh were considered of lower ecological value. 7.5.6 The patches of shrubland habitat recorded in the Assessment Area were considered of low-moderate ecological value, being relatively small, and supporting only one plant species of conservation interest. 7.5.7 Fishpond habitats within the Assessment Area were relatively small, disturbed by human activities, and supported few species of conservation interest. Overall, this habitat type was considered of low-moderate ecological value. 7.5.8 Exotic planted trees and fruit trees dominated plantation and tree/orchard habitats. Species diversity was low-moderate, and no species of conservation interest were recorded from this habitat type. These habitat types were considered of low ecological value. 7.5.9 Developed land, bare ground & wasteland were generally found to be highly disturbed habitats of little ecological interest. The one exception was the disused watchtowers close to estuarine confluence of the PNH, TTT and LTT Rivers. These abandoned buildings have been used previously as a breeding colony by White-shouldered Starling (Sternus sinensis), which is a locally rare breeding species. At least one pair were still recorded breeding in the Towers in 2004.

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7.5.10 In accordance with the EIAO-TM Annex 8 criteria, species of conservation interest recorded in the Assessment Areas are evaluated in Tables 7.3a and 7.3b below.

Table 7.3a Evaluation of Floral Species of Conservation Interest Recorded Within Assessment Areas

Common Name Species Name Growth Protection Distribution Rarity* Form Status Incense Tree Aquilaria Tree Not Common and widespread in Locally sinensis protected. Hong Kong. common but IUCN listed. Small Persimonn Diospyros Shrub Not Common and widespread in Locally very vacciniodes protected. Hong Kong. common but IUCN listed. *Source: Xing et al. 2000

Table 7.3b Evaluation of Faunal Species of Conservation Interest Recorded Within Assessment Areas

Common Name Species Name Protection Distribution/Rarity* Conservation Status Status** Avifauna Grey Heron Ardea cinerea See note 1 Large, secure population of regional PRC significance. Great Egret Egretta alba See note 1 Large, secure population of regional PRC (RC) significance. Little Egret Egretta garzetta See note 1 Large, secure population of regional PRC (RC) significance. Cattle Egret Bubulcus ibis See note 1 Breeding restricted locally. (LC) Chinese Pond Heron Ardeola bacchus See note 1 Large local population is declining. RC Striated Heron Butorides striatus See note 1 Breeding restricted locally. (LC) Black-crowned Night Nycticorax See note 1 Breeding restricted locally. (LC) Heron nycticorax Common Teal Anas crecca See note 1 Large, secure population of regional RC significance. Black Kite Milvus migrans See note 1 Breeding restricted locally. (RC) White-throated Halcyon See note 1 Breeding restricted locally. (LC) Kingfisher smyrnensis Pacific Swift Apus pacificus See note 1 Breeding restricted locally (LC) Zitting Cisticola Cisticola juncidis See note 1 Declining population and locally LC restricted occurrence. Plumbeous Redstart Rhyacornis See note 1 Locally restricted distribution. LC fuliginosus Yellow-breasted Emberiza aureola See note 1 Locally restricted distribution and RC Bunting declining locally. Yellow-billed Eophona See note 1 Locally restricted distribution and LC Grosbeak migratoria declining locally. White-shouldered Sturnus sinensis See note 1 Breeding restricted and declining (LC) Starling locally. Herpetofauna Chinese Bullfrog Rana rugulosa Not Locally uncommon and declining. PRC protected Fish Flagtail Kuhlia marginata Not Locally rare and declining. RC protected Predaceous Chub Parazacco Not Locally common but IUCN listed. - spilurus protected Note 1 – All wild birds are protected under the Wild Animals Protection Ordinance * - Information taken from various sources including Karsen et al., (1998), Carey et al. (2001) and Fellowes et al. (2002).

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** LC – Local Concern (Habitat loss/damage in Hong Kong would pose significant threat to local survival); PRC – Potential Regional Concern (Large, secure populations in Hong Kong are of regional significance); RC – Regional Concern (Habitat loss/damage in Hong Kong would pose significant threat to regional survival); PGC – Potential Global Concern (Large, secure populations in Hong Kong are of global significance); GC – Global Concern (Habitat loss/damage in Hong Kong would pose significant threat to global survival). Refer to Fellowes et al. (2002) for further explanation of status.

7.6 Identification of Environmental Impacts

7.6.1 Potential ecological impacts resulting from construction and operation phase activities have been identified, and are outlined in the following sections.

Construction phase

Direct Impacts

7.6.2 The primary potential impact resulting from the proposed works would be the direct impact to lowland river habitats and associated riparian habitats due to channel construction. The approximate length of affected habitats are:

• Pak Ngau Heung River: 175m • Tai Tei Tong River: 160m • Luk Tei Tong River: 225m • Luke Tei Tong (2) River: 80m 7.6.3 Habitats adjacent to drainage channel improvement works would also be subject to direct impacts (resulting from straightening and widening of existing river and stream channels, construction of LTT (2) River Flood Bypass Channel, construction of ancillary structures and construction of Ling Tsui Tau U-Channel). The approximate areas of affected habitats are summarised in Table 7.4 below: Table 7.4 Habitats Directly Affected by Proposed Drainage Improvement Works*

Habitat Type Pak Ngau Heung Tai Tei Tong Luk Tei Tong Ling Tsui Tau River River Rivers U-Channel Secondary 0.13ha - - <0.01ha Woodland Open Woodland - 0.06ha - - Inactive Wet 0.02ha - 0.8ha - Agriculture Active Dry - - 0.03ha - Agriculture Developed Land - <0.01 0.01ha <0.01ha Wasteland 0.18ha - 0.17ha - Tree/Orchard - - 0.03ha - Total 0.33ha 0.06ha 1.1ha 0.01ha *Aside from River/Stream Habitats

7.6.4 Habitats within the works areas falling outside of the footprint of the proposed channels and associated structures would be subject to temporary disturbance during the construction phase. Additionally, the construction of the PNH Flood Bypass Channel would cause habitat disturbance due to excavation works. These affected habitats would be re-instated following

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the completion of works. Temporary construction phase disturbance is summarised in Table 7.5 below. Table 7.5 Habitats Temporarily Directly Affected by Proposed Drainage Improvement Works*

Habitat Type Pak Ngau Heung Tai Tei Tong Luk Tei Tong Ling Tsui Tau River River Rivers U-Channel Secondary 0.03ha - - 0.02ha Woodland Open Woodland - 0.15ha - - Inactive Wet 0.41ha - 0.56ha - Agriculture Active Dry - - 0.01ha - Agriculture Developed Land 0.09ha 0.05ha 0.07ha 0.17ha Wasteland 0.05ha - 0.07ha - Tree/Orchard - - 0.12ha - Fishpond - - 0.01ha - Total 0.58ha 0.2ha 0.84ha 0.19ha *Aside from River/Stream Habitats 7.6.5 In addition to direct impacts to habitats and vegetation, the proposed works have the potential to cause direct injury/mortality to wildlife. No substantial direct impacts to wildlife with high levels of mobility (e.g., avifauna) are anticipated. Animals with lower mobility (e.g., amphibians, fish) would be at a higher level of risk, and could potentially be injured/killed by construction phase activities. Of particular concern would be potential direct impacts to fish species of conservation interest that have been recorded in the works areas (Flagtail, Kuhlia marginata & Predaceous Chub, Parazacco spilurus). As noted in Section 7.4, avifaunal, herpetofaunal and dragonfly species of conservation interest have previously been recorded from Luk Tei Tong Marsh. However, the area of marsh affected by LTT (2) Bypass Channel construction is substantially degraded (Section 7.5.5 refers) and is unlikely to provide suitable foraging/breeding habitat for these species: direct impacts are therefore considered unlikely. Nevertheless, Chinese Bullfrog (Rana rugulosa) has been recorded from the Luk Tei Tong Marsh area during recent surveys, and could possibly occur within the LTT (2) Bypass Channel works area on an occasional basis. Additionally Romer’s Tree Frog (Philautus romeri) has been recorded from the Mui Wo Area in previous studies. Although not recorded during surveys conducted for this Report, it is possible it could occur within or close to some of the proposed works areas, particularly woodland habitats close to PNH River. Indirect Impacts

7.6.6 Habitat loss summarised in Tables 7.4 and 7.5 would result in reduced foraging opportunities and breeding grounds for some species. With a key concern being the loss of inactive wet agricultural land within Luk Tei Tong Marsh. However, as described in the previous sections, areas of Marsh affected by LTT Bypass Channel construction are not considered a important feeding or potential breeding habitat for species of conservation interest recorded from the Mui Wo Area. 7.6.7 Habitats and associated fauna adjacent to works areas could be subject to disturbance resulting from increased human activities and noise-generating construction plant, with potential disturbance to avifauna in the Assessment Area being a key concern. Noisy

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construction phase activities and general increases in human activity could disturb wildlife utilising habitats close to the works areas. Potential disturbance effects may include the avoidance of areas adjacent to works areas, abandonment of breeding sites, and reductions in wildlife density close to the source of disturbance. 7.6.8 Habitats outside of the works areas could be disturbed as a result of improper storage or dumping of construction material. 7.6.9 Aquatic communities downstream of works areas within existing river channels could be impacted due to increased sedimentation. Increased sedimentation can have a number of adverse effects on aquatic communities. In addition to direct physical damage (particularly to small invertebrate taxon) caused by larger particles (e.g., sand/gravel), small particles (e.g., silt) can clog the respiratory and feeding organs of fish and invertebrates. Increases in turbidity caused by high sediment levels can inhibit photosynthesis by aquatic plants, and impede feeding and other activities in animals that are largely dependant on sight (e.g., some fish species). Dudgeon (1995) studied the effects of increased sedimentation on the macroinvertebrate community of a Hong Kong River, and found substantial decreases in species richness resulting from the impact. A similar response to increased sediment inputs in an Indonesian River was reported by Yule (1995). 7.6.10 Aquatic communities close to works areas could be impacted through potential spills of oils and other pollutants during construction phase. Potential spillage of oils/chemicals could lead to direct lethal/non-lethal effects on aquatic organisms.

Operation phase

7.6.11 Potential direct and indirect impacts to aquatic and riparian communities in newly established channels could result from routine maintenance works such as removal of accumulated sediments and control of vegetation. 7.6.12 Due to the increased capacity of the improved drainage channels, discharge during peak-flow events (such as after extended periods of heavy rain) could be higher than in the existing river channels. Increased discharge could affect aquatic communities, with increased flow rates ‘washing out’ aquatic and riparian plants and animals. 7.6.13 Luk Tei Tong Marsh could be indirectly affected by hydrological disturbance following drainage channel construction. These changes could have an effect on vegetation and aquatic communities within the marsh, and potentially affect the value of the marsh as a feeding resource and potential breeding resource for avifauna and as a habitat for dragonflies, herpetofauna and other wildlife.

7.7 Impact Evaluation

Impacts to Rivers

7.7.1 The scale of impacts to river habitats would be determined largely by the design of drainage channels built to replace existing rivers. Ecological requirements have been considered during the design of drainage improvement works, and are described in the following sections. General layouts of the drainage improvement works are presented in Figs. 2.1-2.3.

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Pak Ngan Heung River

7.7.2 The proposed improvement works to PNH River have been considered to avoid major impacts to natural sections of the River. Drainage improvements would be implemented by constructing an underground channel that would bypass a sharp bend in the river close to Butterfly Hill. Under normal conditions, flow would be maintained within the existing river channel. During high flow events, excess floodwaters would be conveyed through the Bypass Channel, thus avoiding the sharp bend and bottleneck in the River and alleviating flooding risk. 7.7.3 Under this design, modification to the existing PNH River would be limited to two short sections upstream and downstream of the proposed Bypass Channel. At the downstream section, the river channel would be slightly widened, with new vertical concrete retaining walls constructed along the banks of the channel. The channel widening would result in some new sections of riverbed being created, which would be lined with natural materials such as small cobbles and boulders. The existing riverbed and substrates would be retained. 7.7.4 The upstream section of PNH River would be widened and slightly re-aligned. The new channel banks would be trapezoidal in cross-section, and lined with rock-filled gabion. Pits would be provided in the gabion bank to allow for planting and establishment of riparian vegetation. The depth of the new channel bed would be varied to re-create the pool-riffle sequence found in the existing River, and a small weir at the upstream end of the existing river currently maintained for crop irrigation would be re-instated. Similar to the downstream section, the newly constructed sections of riverbed would be lined with natural materials such as cobbles and boulders. Tai Tei Tong River

7.7.5 The original design of drainage improvement works at TTT River included the widening and straightening of approximately 370m of the existing river, leading to the disturbance of much of the slow-flowing lowland section of the river, and the loss of a substantial amount of riparian habitat including numerous mature trees. Following a review of drainage improvement requirements and public consultation, the proposed drainage improvements at TTT River would now be limited to the widening of three small bottlenecks along the existing river, with the total length of the river affected by the works reduced by almost half to 160m. The bottleneck at the downstream end of TTT River (close to the confluence of the three rivers) would be widened along one bank only, with a new concrete retaining wall constructed along this bank. At the two upstream bottlenecks, the newly widened banks would be stabilised with rock-filled gabion. Luk Tei Tong River

7.7.6 The lower section of LTT River would be slightly widened and deepened (total length 225m). Ecological enhancement features to be included along the improved river section would include:

• The channel bed would be constructed using natural materials such as small cobbles and boulders.

• The depth of the channel would be varied to re-create the pool-riffle sequence found in the existing river.

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• The new channel banks would be trapezoidal in cross-section, and lined with rock-filled gabion. Pits would be provided in the gabion bank to allow for planting and establishment of riparian vegetation.

Luk Tei Tong (2) River

7.7.7 The design of drainage improvement works for LTT (2) River has been extensively revised taking into account public consultation during the EIA Study. The proposed works would largely avoid direct impacts to the river by creating a flood bypass channel, with just small sections of the existing river connecting to the upstream and downstream ends of the Bypass Channel affected. Similar to the PNH River, existing flow within the flow LTT (2) River would be maintained under normal conditions, with excess floodwaters diverted to the Bypass Channel during high flow events. Unlike the PNH River Bypass Channel, the LTT Bypass Channel would be open (not routed underground) due to the hydraulic constraints imposed by the high water table in the area. The design of the bypass channel itself is described in the later section 7.8.19. 7.7.8 Using the basic design parameters described in sections 7.7.1-7.7.7 for reference, potential ecological impacts to rivers/streams from construction/operational phase activities, without further mitigation, have been evaluated according to Table 1 of Annex 8 of the EIAO-TM, and are summarised in Tables 7.6a-7.6d below. Table 7.6a Overall Impact Evaluation to Pak Ngan Heung River.

Evaluation Pak Ngan Heung River Criteria Habitat quality Moderate-high Species Potential disturbance and temporary habitat loss for avifauna species of conservation interest, (Grey Heron, Ardea cinerea; Little Egret, Egretta garzetta; Chinese Pond Heron, Ardeola bacchus; Striated Heron, Butorides striatus; Black-crowned Night Heron, Nycticorax nycticorax; White-throated Kingfisher, Halcyon smyrnensis; and Plumbeous Redstart, Rhyacornis fulignosus).

Potential direct impact, disturbance and temporary habitat loss for fish species of conservation interest (Flagtail, Kuhlia marginata & Predaceous Chub, Parazacco spilurus) Size/Abundance Two small sections of the river totaling approximately 175m in length would be directly affected Duration Direct impacts would last for the duration of the construction phase, and a period of re-colonisation during the operation phase.

Periodic minor disturbance throughout the operation phase due to routine maintenance (e.g., de-silting works). Reversibility Direct impacts to river habitat would be reversible; the newly constructed channel sections are expected to provide suitable habitats for aquatic communities previously recorded from the river.

Periodic minor increase in disturbance during operational phase would be temporary and reversible. Magnitude The scale of the impacts is considered minor-moderate, given the relatively short sections of river affected. Overall impact Construction Phase: Moderate. conclusion Operation Phase: Minor.

Table 7.6b Overall Impact Evaluation to Tai Tei Tong River.

Evaluation Tai Tei Tong River Criteria Habitat quality Moderate

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Evaluation Tai Tei Tong River Criteria Species Potential disturbance and temporary habitat loss for avifauna species of conservation interest, (Little Egret, Egretta garzetta; Chinese Pond Heron, Ardeola bacchus; Striated Heron, Butorides striatus).

Potential direct impact, disturbance and temporary habitat loss for fish species of conservation interest (Predaceous Chub, Parazacco spilurus) Size/Abundance Three small sections of the river totaling approximately 160m in length would be directly affected Duration Direct impacts would last for the duration of the construction phase, and a period of re-colonisation during the operation phase.

Periodic minor disturbance throughout the operation phase due to routine maintenance (e.g., de-silting works). Reversibility Direct impacts to stream/river habitats would be reversible; the newly constructed drainage channels are expected to provide suitable habitats for aquatic communities previously recorded from the stream/river.

Periodic minor increase in disturbance during operational phase would be temporary and reversible. Magnitude The scale of the impacts is considered minor. Overall impact Construction Phase: Minor. conclusion Operation Phase: Minor.

Table 7.6c Overall Impact Evaluation to Luk Tei Tong River.

Evaluation Luk Tei Tong River Criteria Habitat quality Moderate Species Potential disturbance and temporary habitat loss for avifauna species of conservation interest, (Great Egret, Casmerodius alba; Little Egret, Egretta garzetta; Striated Heron, Butorides striatus; Black-crowned Night Heron, Nycticorax nycticorax; White-throated Kingfisher, Halcyon smyrnensis; and Common Teal, Anas crecca). Size/Abundance 225m of river channel directly affected Duration Direct impacts would last for the duration of the construction phase, and a period of re-colonisation during the operation phase.

Periodic minor increase in disturbance during operational phase would be temporary and reversible. Magnitude The scale of the impacts is considered minor-moderate. Overall impact Construction Phase: Moderate. conclusion Operation Phase: Minor.

Table 7.6d Overall Impact Evaluation to Luk Tei Tong (2) River.

Evaluation Luk Tei Tong (2) River Criteria Habitat quality Low-moderate. Species Potential disturbance and temporary habitat loss for avifauna species of conservation interest, White-throated Kingfisher, Halcyon smyrnensis. Size/Abundance Impacts limited to two very small sections of the river totaling about 80m in length at the upstream and downstream ends of the proposed bypass channel.

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Evaluation Luk Tei Tong (2) River Criteria Duration Direct impacts would last for the duration of the construction phase, and a period of re-colonisation during the operation phase.

Periodic minor increase in disturbance during operational phase would be temporary and reversible. Magnitude The scale of the impacts is considered very minor. Overall impact Construction Phase: Very Minor. conclusion Operation Phase: Very Minor.

Construction Phase Direct Impacts 7.7.9 Impacts to PNH and LTT Rivers are considered moderate in scale during and immediately after the construction phase. During this period, there would be localised disturbance to aquatic and riparian communities. This would include potential direct impacts and disturbance to fish species of conservation interest recorded from the rivers (Flagtail, Kuhlia marginata & Predaceous Chub, Parazacco spilurus). Overall impacts to these watercourses are rated moderate in scale only, as the design of drainage channels replacing the affected river sections would provide a suitable habitat for existing aquatic communities recorded in the rivers/streams. Following the re-establishment of aquatic and riparian habitats, longer-term impacts would be relatively minor. 7.7.10 Direct impacts to TTT and LTT (2) Rivers are considered relatively minor due to the limited scale of works proposed at these rivers.

Indirect Impacts Due to Construction Phase Habitat Loss and Disturbance 7.7.11 Impacts to waterfowl and other wildlife using the rivers would result from temporary loss of feeding habitats and disturbance caused by habitat loss, increased human activity and noise generating construction phase activities. On the whole, these impacts are considered relatively minor, as construction phase disturbance impacts would be temporary and generally short-lived in nature (please refer to the Construction Programme in Appendix 2.2 for details), and the newly created drainage channels are expected to provide suitable foraging grounds for waterfowl and other wildlife using the existing river channels. Furthermore, as works would be confined to relatively short sections of each river, wildlife (particularly avifauna) potentially displaced or disturbed by the proposed works would be able to ultilise less disturbed river sections during the construction phase. Potential indirect impacts resulting from construction phase habitat loss and disturbance at each river are summarised as follows:

• Impacts to PNH River are expected to be minor in scale only. Works at the downstream and upstream sections of river to be improved would not be conducted concurrently, with the downstream works limited to two consecutive dry seasons (Nov.-March). Works on the upstream section would commence following

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completion of downstream section, and are scheduled to be completed in just over a year.

• Impacts to LTT river are expected to be minor-moderate in scale. The works period is scheduled to last for approximately one and a half years in total, although works would not be conducted along the whole channel concurrently.

• Indirect disturbance impacts resulting from works at TTT and LTT (2) Rivers are expected to be very minor in scale. Works at the three bottlenecks at TTT River would be completed within 3-5months at each location, and would not be conducted concurrently. All works at LTT (2) River would be finished within one dry season (Nov.-Mar.).

Indirect Impacts Due to Increased Sedimentation and Other Water Quality Impact 7.7.12 Construction methods described in Section 5 of this report would serve to limit sedimentation impacts to aquatic communities in sections of the Rivers downstream of the proposed works areas. The excavation works would be carried out by land-based plant. Impacts would be further minimised by restricting the excavation works to an enclosed dry section of the river. Containment measures such as bunds and barriers would be used within the river to minimize the impacts upon the downstream water body. 7.7.13 With these measures in place, sedimentation is expected to have only local and temporary effects on water quality and aquatic ecology. These impacts are therefore considered relatively minor. 7.7.14 Indirect impacts resulting from potential spills of oils and other pollutants during construction phase are considered relatively minor. Standard good construction practice and simple mitigation measures would limit the scale and incidence of potential impacts.

Operation Phase Impacts

7.7.15 Disturbance impacts resulting from maintenance works such as de-silting operations and vegetation management are expected to result in minor ecological impacts only. Works would be limited to localised areas of the river channels, and would be conducted on an annual or bi-annual basis. Disturbance impacts resulting from the works (e.g., reduction in vegetation cover, removal of sediments) would be temporary and reversible in nature. 7.7.16 Due to the increased drainage capacity of the TTT and LTT River channels, discharge during peak-flow events (such as after extended periods of heavy rain) could be higher than in the existing channels. Increased discharge could affect aquatic communities, with increased flow rates ‘washing out’ aquatic and riparian plants and animals. 7.7.17 Flooding events in watercourses is a natural and relatively frequent phenomenon in Hong Kong owing to the monsoonal climate which delivers heavy rains in summer, causing watercourses to flow in spate. During spate, aquatic communities are affected due to increased flow rates causing “washing-out” of aquatic and riparian plants and animals. Locally, lotic communities are well adapted to survive flood spates. For example: many insects with aquatic life-cycle larval stage time the emergence of adult stage before the wet season, therefore avoiding peak flow events (Dudgeon, 1999). Stream fish also have

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behavioural adaptations to high flow rate by taking refuge between bottom substrate on the streambed. 7.7.18 The improved capacity of the rivers would not be expected to cause significant impact to stream organisms beyond natural impacts under normal summer flood spates. During higher magnitude flood events, flow velocity in the channelised streams with improved drainage capacity would be expected to be greater than existing stream channels. These infrequent and temporary high flow rate conditions are not expected to have long-term negative adverse impacts on aquatic communities in the rivers. Impacts on aquatic insects are unlikely to be significant due to their avoidance of high flow conditions. Owing to the natural substrate of the channels, freshwater stream fish populations would have suitable streambed refuges to escape temporary high flow conditions.

Impacts to Other Habitats

7.7.19 Potential ecological impacts to habitats aside from rivers, if unmitigated, have been evaluated according to Table 1 of Annex 8 of the EIAO-TM, and are summarised in Tables 7.6e-7.6h below.

Table 7.6e Overall Impact Evaluation of Woodland and Active Agriculture (Dry & Wet) Habitats.

Evaluation Woodland Active Agriculture (Dry & Wet) Criteria Habitat quality Secondary Woodland: Moderate. Low. Open Woodland: Low-moderate. Species Potential direct impact to Romer’s Tree Frog. No direct impact to species of conservation interest, although there may be potential indirect Potential indirect impact to wildlife due to impact to wildlife. construction phase disturbance. Size/Abundance Direct impact to 0.13ha of secondary woodland Direct impact to 0.03ha of Active Agricultural due to PNH River Channel Construction. Land due to TTT River Channel Construction.

Direct impact to <0.01ha of secondary woodland due to Ling Tsui Tau U-Channel Construction.

Direct impact to 0.06ha of open woodland due to TTT River bottleneck widening. Duration Loss of habitat would be permanent. Loss of habitat would be permanent.

Indirect impacts such as noise disturbance would Indirect impacts such as noise disturbance would be largely limited to the construction phase. be largely limited to the construction phase. Reversibility Loss of habitat would be irreversible. Loss of habitat would be irreversible.

Indirect disturbance impacts would be temporary Indirect disturbance impacts would be temporary and reversible. and reversible. Magnitude The scale of the impact is considered low. The scale of the impact is considered low. Overall impact Low-moderate. Very Low conclusion

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Table 7.6f Overall Impact Evaluation of Inactive Agriculture (Dry & Wet) and Shrubland Habitats

Evaluation Inactive Agriculture (Dry & Wet) Shrubland Criteria Habitat quality Luk Tei Tong Marsh: Moderate-high Low-moderate. Other Inactive Agriculture: Low-moderate. Species Potential direct impact to Chinese Bullfrog. No impact. Potential indirect impact to wildlife due to construction phase disturbance. Size/Abundance Direct and permanent impact to 0.8ha of Luk Tei No impact. Tong Marsh due to LTT River & LTT (2) River Channel Construction, although affected area of marsh is fairly dry, disturbed and not considered of particular ecological interest.

Direct impact to 0.02ha of low-moderate ecological value inactive agricultural land due to PNH River Channel Construction. Duration Loss of habitat would be permanent. No impact.

Indirect impacts such as noise disturbance would be largely limited to the construction phase. Reversibility Loss of habitat would be irreversible. No impact.

Indirect impacts such as noise disturbance would be largely limited to the construction phase. Magnitude Luk Tei Tong Marsh: Low-moderate. No impact. Other Inactive Agriculture: Low. Overall impact Luk Tei Tong Marsh: Moderate. No impact. conclusion Other Inactive Agriculture: Low.

Table 7.6g Overall Impact Evaluation of Fishpond and Plantation & Tree/Orchard Habitats

Evaluation Fishponds Plantation & Tree/Orchard Criteria Habitat quality Low-Moderate. Low. Species No direct impact to species of conservation No direct impact to species of conservation interest, although there may be potential indirect interest, although there may be potential indirect impact to wildlife. impact to wildlife. Size/Abundance No direct impact to fishpond habitats. Direct impact to 0.03ha of tree/orchard habitat due to LTT River Channel Construction. Duration Indirect impacts such as noise disturbance would Loss of habitat would be permanent. be largely limited to the construction phase. Indirect impacts such as noise disturbance would be largely limited to the construction phase. Reversibility Indirect disturbance impacts would be temporary Loss of habitat would be irreversible. and reversible. Indirect disturbance impacts would be temporary and reversible. Magnitude The scale of the impact is considered low. The scale of the impact is considered very low. Overall impact Low. Very Low. conclusion

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Table 7.6h Overall Impact Evaluation of Developed Land, Bare Ground & Wasteland Habitats

Evaluation Developed Land, Bare Ground & Wasteland Criteria Habitat quality Very Low. Species No direct impact to species of conservation interest, although there may be potential indirect impact to wildlife. Size/Abundance Direct impact to 0.18ha of disturbed habitat due to PNH River Channel Construction.

Direct impact to 0.18ha of disturbed habitat due to LTT River Channel Construction.

Direct impact to <0.01ha of disturbed habitat due to Ling Tsui Tau U-Channel Construction. Duration Loss of habitat would be permanent.

Indirect impacts such as noise disturbance would be largely limited to the construction phase. Reversibility Loss of habitat would be irreversible.

Indirect disturbance impacts would be temporary and reversible. Magnitude The scale of the impact is considered very low. Overall impact Negligible. conclusion

Construction Phase Impacts Direct Impacts 7.7.20 Direct impacts to habitats other than Rivers (discussed in Sections 7.7.8-7.7.10 above) would include small areas of relatively low ecological value habitat (open woodland, active agricultural land, inactive agricultural land, tree/orchard and disturbed areas). These impacts are considered minor in scale. 7.7.21 The most substantial direct impact identified would be to Luk Tai Tong Marsh. It is estimated that 0.8ha of the marsh would be directly impacted due to the LTT River improvements and construction of the LTT (2) Bypass Channel. Further to this, approximately 0.56ha of marsh habitat that falls within the proposed works area (but outside of the channel alignments) would be temporarily impacted during the construction phase. The marsh is considered of moderate-high ecological value due to its importance as a foraging ground and potential breeding habitat for avifauna, herpetofauna and insects (as determined by a review of literature and surveys conducted for this Report). However, it should be noted that direct impacts to the marsh would largely be limited to the area north of Luk Tei Tong Village. As described in Section 7.4.15, this area was found to be drier, dominated by the exotic weed Mikania micrantha, and was subject to higher levels of disturbance than marsh areas to the north-east and north-west of the village. The impacted areas are not considered a key foraging or breeding habitat for wetland species that may occur within the Marsh area. For these reasons, impacts to Luk Tei Tong Marsh were considered moderate in scale only. 7.7.22 Impacts to secondary woodland habitat resulting from the Project would be limited to the loss of very small areas (totalling 0.13ha) of woodland fringe at the base of Butterfly Hill due to PNH River and Ling Tsui Tau U-Channel construction. There would be additional disturbance to approximately 0.05ha of secondary woodland habitat within the PNH River and Ling Tsui Tau U-Channel Works Areas during the construction phase. Although the area of habitat affected is small, secondary woodland habitat is considered of moderate ecological value, and provides a potential breeding habitat for RTF. The loss of woodland habitat would

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therefore require mitigation. No impacts to the two plant species of conservation interest recorded from woodland habitat (Aquilaria sinensis and Diospyros vaccinioides) are expected. 7.7.23 As discussed in Section 7.6.5, the proposed works have the potential to cause direct injury/mortality to wildlife. Animals with low mobility would potentially be at risk, including two amphibian species of conservation interest (Chinese Bullfrog, Rana rugulosa and Romer’s Tree Frog , Philautus romeri) that could occur within the works areas. Any possible injury/mortality to individuals of these species is considered a moderate-high (Chinese Bullfrog) or high level (Romer’s Tree Frog) impact, and would require mitigation.

Indirect Impacts Due to Construction Phase Disturbance 7.7.24 Indirect impacts to habitats and associated communities adjacent to the works areas could result from increased human activities/disturbance during the construction phase. Such impacts would arise from noise-generating machinery, general increases in human activity, and potential improper storage or dumping of construction material. The ecological effects of disturbance are complex and difficult to measure (Treweek, 1999), and therefore the extent to which any particular disturbance source affects nearby communities is difficult predict with any degree of accuracy. With regard to the current Project, the greatest concern would be disturbance to wildlife (particularly avifauna) utilising areas of Luk Tei Tong Marsh close to the proposed Luk Tei Tong Bypass Channel works area, and also potential disturbance close to the Disused Watchtowers, which are used as a nesting site by the locally rare White-Shouldered Starling (Sternus sinensis). The scale of potential disturbance to these two sensitive receivers is discussed in the following sections. 7.7.25 Disturbance impacts to Luk Tei Tong Marsh are anticipated to be minor in scale only. This prediction is based largely upon the short construction period for the LTT (2) River Bypass Channel, with works anticipated to be completed within five months. Furthermore, as the works would be completed within the dry season, minimal impacts to avifauna that may use the marsh as a breeding habitat are expected. Finally, works (and therefore potential disturbance impacts) would largely be restricted to a small area of degraded habitat to north of Luk Tei Tong Village which forms less than 10% of the total marsh area; large areas of the marsh (including more established and less disturbed areas of the marsh to the northeast and northwest of the Village) would remain relatively undisturbed during the construction period. It is therefore likely that any birds subject to disturbance from the proposed works would relocate to undisturbed areas of the marsh further from the works area. 7.7.26 Disturbance close to the Disused Watchtowers, which are used as a nesting site by the locally rare White-Shouldered Starling (Sternus sinensis), would largely be avoided through the scheduling of the proposed works programme. Works close to the disused Watchtowers (at the river outlets) is scheduled for the dry season only (November-March). This would avoid the main breeding season of the Starling, which is in the wet season (generally starting in May, Viney et al., 1994).

Operation Phase Impacts Disturbance Resulting From Maintenance Works 7.7.28 Disturbance impacts resulting from maintenance works such as de-silting operations and vegetation management are not expected to substantially affect habitats outside of the river channels; Works would be limited to localised areas of the river channels, and would be

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conducted on an annual or bi-annual basis. Any disturbance impacts resulting from these activities would be temporary and reversible in nature.

Hydrological Disturbance 7.7.29 Hydrological disturbance to Luk Tei Tong Marsh is expected to be minor. The LTT (2) River Bypass Channel (which would run through the marsh) would only be slightly lower (by approximately 800mm) than the surrounding area of marsh, and no substantial ‘draining down’ of the marsh is anticipated. Furthermore, each bank of the proposed Bypass Channel would be topped with a low (200mm high) earth bund, which would prevent surface water in the marsh from draining into the Bypass Channel. Impacts resulting from increased drainage of the marsh into the Channel are therefore expected to be negligible. 7.7.30 The LTT (2) Bypass Channel would contain floodwaters during periods of heavy rainfall that currently inundate areas of Luk Tei Tong Marsh. Under existing conditions, floodwaters from the River only inundate the Marsh once every few years, with floodwaters usually receding within a few hours. The cessation of these occasional and ephemeral flooding events is therefore expected to have a negligible impact on the ecology of the Marsh.

Cumulative Impacts 7.7.31 The proposed drainage improvement works discussed in this Chapter are scheduled to begin in mid 2006 and end in mid 2009. One other Project in the Assessment Area, ‘construction of emergency vehicular access and sewerage at Luk Tei Tong, Mui Wo’ (hereafter referred to as EVA) would still be under construction during this period, with works scheduled for completion towards the end of 2006. Because of the short overlap in the construction programmes of the two Projects, there is some scope for cumulative ecological impacts resulting from increased disturbance levels. However, the EVA works would largely be confined to the area between Tai Tei Tong Village to the north and Luk Tei Tong Village to the south. No drainage improvement works are scheduled to be conducted in this area until April 2007, when widening of the upstream bottleneck at Tai Tei Tong River is due to commence (Appendix 2.1 refers). It is therefore anticipated that cumulative disturbance impacts resulting from the two Projects would be very minor.

Impacts to Species of Conservation Interest

7.7.32 Potential impacts to species of conservation interest recorded during recent surveys are described in sections 7.7.9-7.7.31 above, and summarised in Table 7.7 below. 7.7.33 Further to species recorded during recent surveys conducted for this Report, a number of wildlife species of conservation interest have been recorded from Mui Wo Area in previous surveys, and could still occur in the Assessment Area. Of particular concern are potential direct and indirect impacts to RTF, which are considered moderate-high in scale (section 7.7.23 refer). Potential impacts to RTF are also summarised in Table 7.7.

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Table 7.7 Overall Impact Evaluation to Species of Conservation Interest

Species of Conservation Interest Construction Phase Impacts Operation Phase Impacts Common Name Scientific Name Description Evaluation Description Evaluation Flora Incense Tree Aquilaria sinensis Individuals of these species fall outside of works areas, no No impact. Individuals of these species fall outside of works areas, No impact. Small Persimonn Diospyros impacts predicted. No Impact. no impacts predicted. No Impact. vaccinioides

Fauna Avifauna Grey Heron Ardea cinerea Grey Heron recorded from lower PNH River. Impacts Low. Following re-establishment, newly constructed Very Low. anticipated to result from temporary loss of feeding habitats drainage channels expected to provide suitable foraging due to river channel construction, and disturbance caused by habitat for this species. Impacts would be limited to increased human activity and noisy construction phase periodic and temporary disturbance due to maintenance activities. works. Great Egret Egretta alba Great Egret recorded from lower LTT River. Impacts Low. Following re-establishment, newly constructed Very Low. anticipated to result from temporary loss of feeding habitats drainage channels expected to provide suitable foraging due to river channel construction, and disturbance caused by habitat for this species. Impacts would be limited to increased human activity and noisy construction phase periodic and temporary disturbance due to maintenance activities. works. Little Egret Egretta garzetta Little Egret recorded largely from river habitats. Impacts Low. Following re-establishment, newly constructed Very Low. anticipated to result from temporary loss of feeding habitats drainage channels expected to provide suitable foraging due to river channel construction, and disturbance caused by habitat for this species. Impacts would be limited to increased human activity and noisy construction phase periodic and temporary disturbance due to maintenance activities. works. Cattle Egret Bubulcus ibis Cattle Egret recorded from river and marsh habitats. Impacts Low. Impacts would be limited to loss of small area of marsh Very Low. anticipated to result from permanent loss of small areas of habitat, and periodic and temporary disturbance due to marsh habitat, temporary loss of feeding habitats due to river maintenance works. channel construction, and disturbance caused by increased human activity and noisy construction phase activities. Chinese Pond Heron Ardeola bacchus Chinese Pond Heron various habitats within the Assessment Low. Following re-establishment, newly constructed Very Low. Area. Impacts anticipated to result from permanent loss of drainage channels expected to provide suitable foraging small areas of marsh habitat, temporary loss of feeding habitat for this species. Impacts would be limited to habitats due to river channel construction, and disturbance loss of small area of marsh habitat, and periodic and caused by increased human activity and noisy construction temporary disturbance due to maintenance works. phase activities. Striated Heron Butorides striatus Striated Heron recorded from river/stream habitats within the Low. Following re-establishment, newly constructed Very Low. Assessment Area. Impacts anticipated to result from drainage channels expected to provide suitable foraging temporary loss of habitat due to river channel construction, habitat for this species. Impacts would be limited to

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Species of Conservation Interest Construction Phase Impacts Operation Phase Impacts Common Name Scientific Name Description Evaluation Description Evaluation and disturbance caused by increased human activity and noisy periodic and temporary disturbance due to maintenance construction phase activities. works. Black-crowned Night Nycticorax Night Heron recorded from estuarine and downstream reaches Low. Following re-establishment, newly constructed Very Low. Heron nycticorax of the rivers. Impacts anticipated to result from temporary loss drainage channels expected to provide suitable foraging of feeding habitats due to river channel construction, and habitat for this species. Impacts would be limited to disturbance caused by increased human activity and noisy periodic and temporary disturbance due to maintenance construction phase activities. works. Common Teal Anas crecca Teal recorded from LTT River. Impacts anticipated to result Low. Following re-establishment, newly constructed Very Low. from temporary loss of feeding habitats due to river channel drainage channels expected to provide suitable foraging construction, and disturbance caused by increased human habitat for this species. Impacts would be limited to activity and noisy construction phase activities. periodic and temporary disturbance due to maintenance works. Black Kite Milvus migrans Black Kite recorded soaring over the Assessment Area. Negligible. No impact. No Impact. Negligible impact anticipated. White-throated Halcyon smyrnensis Kingfishers recorded from various habitats within the Low. Following re-establishment, newly constructed Very Low. Kingfisher Assessment Area. Impacts anticipated to result from drainage channels expected to provide suitable foraging permanent loss of small areas of marsh habitat, temporary loss habitat for this species. Impacts would be limited to of feeding habitats due to river channel construction, and periodic and temporary disturbance due to maintenance disturbance caused by increased human activity and noisy works. construction phase activities. Pacific Swift Apus pacificus Recorded flying over Assessment Area. No impact predicted. No Impact Recorded flying over Assessment Area. No impact No Impact predicted. Zitting Cisticola Cisticola juncidis Zitting Cisticola recorded from Luk Tei Tong Marsh. Impacts Low-moderate. Impacts would be limited to loss of small area of marsh Very Low. anticipated to result from temporary and permanent loss of habitat, and periodic and temporary disturbance due to habitat due to channel construction, and disturbance caused by maintenance works. increased human activity and noisy construction phase activities Plumbeous Redstart Rhyacornis Plumbeous Redstart recorded from PNH River. Impacts Low. Following re-establishment, newly constructed Very Low. fuliginosus anticipated to result from temporary loss of feeding habitat drainage channels expected to provide suitable foraging due to river channel construction, and disturbance caused by habitat for this species. Impacts would be limited to increased human activity and noisy construction phase periodic and temporary disturbance due to maintenance activities. works. Yellow-breasted Bunting Emberiza aureola Buntings recorded from Luk Tei Tong Marsh area. Impacts Low-moderate. Impacts would be limited to small loss of marsh habitat, Very Low. anticipated to result from temporary and permanent loss of and periodic and temporary disturbance due to feeding habitats due to channel construction, and disturbance maintenance works. caused by increased human activity and noisy construction phase activities. Yellow-billed Grosbeak Eophona Grosbeak recorded flying over the Assessment Area. Impacts Very Low. No impact. No Impact. migratoria expected to be minor. White-shouldered Sturnus sinensis Starlings recorded breeding in the disused watchtowers. Moderate. Impacts would be limited to periodic and temporary Very Low.

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Species of Conservation Interest Construction Phase Impacts Operation Phase Impacts Common Name Scientific Name Description Evaluation Description Evaluation Starling Potential construction phase disturbance to breeding birds disturbance due to maintenance works. would largely be avoided, but is still considered a potentially low-moderate impact.

Herpetofauna Chinese Bullfrog Rana rugulosa Potential direct impact to this species during construction Moderate-high Impacts to Luk Tei Tong Marsh would result in loss of Low-moderate phase.. small area of habitat for this species, although newly constructed LTT (2) Channel would provide partial compensation for habitat loss. Romer’s Tree Frog Philautus romeri Potential direct impact to this species during construction High Impact to 0.13ha woodland habitat would be Very Low phase. permanent, although the affected area is small in the context of similar habitats in the Mui Wo area as a whole.

Fish Flagtail Kuhlia marginata Potential direct impact to these species’ during construction Moderate-high Following re-establishment, newly constructed Low Predaceous Chub Parazacco spilurus phase. Potential disturbance during construction phase due to Low-moderate drainage channels expected to provide suitable habitats Low habitat loss and increased sedimentation. for these fish species. Impacts would be limited to periodic and temporary disturbance due to maintenance works.

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Agreement No. CE49/2002 (DS) Drainage Improvement in Southern Lantau Drainage Services Department Final EIA Report

7.8 Mitigation of Adverse Environmental Impacts

7.8.1 Following EIAOTM Annex 16 guidelines mitigation measures are proposed in this section to avoid, minimise and compensate for identified ecological impacts.

Avoidance

7.8.2 The design of drainage improvement works has been considered to avoid impacts to existing river habitats where possible (Sections 7.7.1-7.7.7 refer). For example, the adoption of a flood bypass channel for LTT (2) River would largely avoid impact to the existing LTT (2) River. 7.8.3 The works programme has been considered to avoid impacts to breeding wildlife where possible. For example, works within Luk Tei Tong Marsh and the confluence of the three rivers would be restricted to the dry season, thereby avoiding impacts to White-shouldered Starlings (Sternus sinensis) that have been recorded breeding in the Disused Watchtowers close to the river confluence, and also to other avifauna and herpetofauna species that may breed within Luk Tei Tong Marsh and adjacent areas.

Minimising

General

7.8.4 Where avoidance of impacts has proved impracticable, the design of drainage improvement works have been considered to minimise impacts to existing river habitats (Sections 7.7.1-7.7.7 refer). For example, the scope of works along the TTT River have been much reduced in scale from the originally proposed drainage improvements. The original design called for the widening and straightening of approximately 370m of the existing river, leading to the disturbance of much of the slow-flowing lowland section of the river, and the loss of a substantial amount of riparian habitat including numerous mature trees. Following a review of drainage improvement requirements and public consultation, the proposed drainage improvements at TTT River would now be limited to the widening of three small bottlenecks along the existing river, with the total length of the river affected by the works reduced by almost half to 160m. 7.8.5 All excavation works carried out within or close to water bodies should be carried out in the dry season where possible, with construction carried out by land-based plant. Excavation works within river/stream channels should be restricted to an enclosed dry section of the river, with containment measures such as bunds and barriers used within the river to minimize the impacts upon the downstream water body. Site runoff should be directed towards regularly cleaned and maintained silt traps and oil/grease separators to minimise the risk of sedimentation and pollution of river water. The silt and oil/grease separators should be appropriately designed for the local drainage and ground conditions. To minimize leakage and loss of sediments during excavation in narrow channels, tightly sealed closed grab excavators should be deployed where material to be handled is wet. 7.8.6 Noise mitigation measures including the use of quiet construction plant and temporary noise barriers (Section 4 of the report refers) should be implemented to minimise disturbance to habitats adjacent to the works areas. 7.8.7 Standard good site practice measures should be implemented throughout the construction phase. The measures should include:

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• Placement of equipment or stockpile in designated works areas and access routes selected on existing disturbed land to minimise disturbance to natural habitats and vegetation, particularly mature trees. • Construction activities should be restricted to work areas that should be clearly demarcated. The work areas should be reinstated after completion of the works. • Waste skips should be provided to collect general refuse and construction wastes. The wastes should be disposed of timely and properly off-site. • General drainage arrangements should include sediment and oil traps to collect and control construction site run-off. • Open burning on works sites is illegal, and should be strictly prohibited.

7.8.8 Potential operational phase activities in newly constructed river channels would be limited to regular channel maintenance such as de-silting. Impacts to aquatic communities resulting from these activities are expected to be minor. Nevertheless, the following measures are recommended to minimise potential impacts resulting from operational phase activities:

• To minimise sedimentation, de-silting should be limited to the dry season (November-March). • For maintenance desilting of the re-profiled river channels, temporary barrier walls shall be used to provide a dry zone for desilting work. • The implementation of de-silting and other activities that could disturb aquatic fauna should be phased to ensure some areas of relatively undisturbed habitat remain available for resident aquatic fauna at all times. • Waste material produced during de-silting should be disposed of in a timely and appropriate manner.

Luk Tei Tong Bypass Channel

7.8.9 A standard design feature of most engineered drainage channels in Hong Kong is the inclusion of a footpath or access road along one or both banks of the channel. To minimise impacts to Luk Tei Tong Marsh, no footpath would be constructed along the by-pass channel. 7.8.10 Construction of the Bypass Channel would be limited to one dry season only, thereby minimising disturbance impacts to wetland fauna potentially breeding in the Marsh Area. 7.8.11 Operation phase impacts resulting from desilting works within the LTT (2) Bypass Channel are expected to be very minor in scale, given that water flow (and therefore sediment deposition) within the channel would be minimal for much of the year, except during spate events. Vegetation control would be required 1-2 times per year at most to prevent the excessive growth of (especially woody) vegetation that would impede the drainage capacity of the channel. These measures do not necessarily conflict with the maintenance of the channel as marshland, as the removal and control of vegetation would be required anyway to maintain the sub-climatic vegetation community found in marsh habitats. It is recognised, however, that regular cutting of vegetation could prevent the re-establishment of wetland communities, with potential disturbance to breeding fauna of particular concern. It is therefore recommended that vegetation control is undertaken outside of the main breeding season for wildlife (April-August) to avoid potential impacts.

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Ling Tsui Tau U-Channel

7.8.12 The construction of the Ling Tsui Tau U-Channel is expected to cause minor impacts to woodland habitats close to Butterfly Hill. To minimise these impacts, the results of the Tree Survey Report for this Project should be considered when finalising the alignment of the proposed works. The U-Channel alignment should be ‘fine-tuned’ to avoid nearby mature trees. Impacts to Fish and Amphibian Species of Conservation Interest

7.8.13 As discussed in Section 7.7.9, proposed works at the rivers have the potential to impact fish species of conservation interest. To minimize these potential impacts, it is recommended that capture-surveys of the proposed works areas are conducted prior to the commencement of construction works in the channel. These surveys should include fish species of conservation interest recorded during the surveys (Flagtail, Kuhlia marginata & Predaceous Chub, Parazacco spilurus), with particular attention paid to the Flagtail. Either of these species caught during the surveys should be re-located to areas of the watercourse upstream of the proposed works areas, or to aquaria set up close to the works areas. Maintenance of the fish prior to translocation would be undertaken by an ecologist appointed by the Project Proponent. The capture surveys should be conducted in the dry season by a suitably qualified ecologist(s) appointed by the Project Proponent. For the Flagtail (which will probably occur in low densities at PNH River), further surveys should be conducted to confirm the presence and numbers of fish in the streams closer to the time of construction. A detailed methodology for fish translocation (based in part upon the Flagtail survey results) should be formulated during the detailed design stage of the Project. 7.8.14 In addition to fish species of conservation interest, the proposed drainage improvement works could also result in direct impacts to two amphibian species of conservation interest, RTF and Chinese Bullfrog. It is therefore recommended that additional capture surveys are conducted prior to the commencement of works to locate any individuals of these two species within the works areas. The surveys should be conducted in the wet season (March/April-October), when these species are calling and are generally more conspicuous. Any individuals captured during the survey should be relocated to similar nearby habitats outside of the works areas. The capture surveys should be conducted by a suitably qualified ecologist(s) appointed by the Project Proponent. A detailed methodology for faunal translocation should be formulated during the detailed design stage of the Project.

Compensation

Rivers

7.8.15 Various features have been incorporated into the design of drainage channels to minimise long-term loss of river habitat resulting from the Project (Section 7.7.1-7.7.7 refers). Following a period of establishment and re-colonisation, the newly created channels are expected to provide a suitable habitat for aquatic communities recorded in the existing rivers. 7.8.16 As the new drainage channels would be approximately the same width as the existing watercourses, it is anticipated that most of the substrates used to line the new channel beds can be taken from the existing rivers. Rocks unearthed during excavation works for this Project or material purchased from local quarries would be used as material to fill gabion bank linings and as additional substrate to line the riverbeds if required

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7.8.17 In time, it is expected that vegetation will naturally re-colonise newly constructed channel sections. To expedite this process, planting of suitable aquatic, emergent and riparian plant species within the beds and gabion-lined sections of channels will be undertaken following the completion of works (Table 2.7 lists some suggested species for use in this planting). Additionally, the gabion lining will be hydroseeded. Planting design will be finalised in the detailed design stage. 7.8.18 The newly created PNH River drainage channel is expected to provide a suitable habitat for the fish species of conservation interest (Flagtail, Kuhlia marginata) previously recorded from the river. To further increase the value of the PNH River for this and other fish species, it is recommended that a small fish ladder is constructed at the upstream end of the new channel. The existing agricultural weir at this location currently impedes the movement of fish between upstream and downstream sections of the river. The fish ladder would facilitate movement past this obstacle, extending the range of fish communities in both upstream and downstream areas. A conceptual layout of the proposed fish ladder is given in Figure 7.3, showing a basic design of rock-ramp fishway commonly adopted in Australia and other countries to facilitate the passage of various fish species over low obstructions. The detailed design of the ladder would be finalised at a later stage of this Project.

Luk Tei Tong Marsh

7.8.19 As outlined in Table 7.4, the proposed Luk Tei Tong River drainage improvement works and Luk Tei Tong By-pass Channel would result in the permanent loss of approximately 0.8ha of habitat within the Luk Tei Tong Marsh Area. Although the affected area was found to be degraded and of less ecological interest than more established areas of the Marsh, the proposed Luk Tei Tong Bypass Channel has been designed to incorporate wetland habitats, providing compensation and enhancement of habitats within the channel alignment. The area of marsh habitat within the Channel is depicted in Figure 7.2, and a typical cross-section of the proposed Bypass Channel is shown in Figure 2.3. The following key features would be included in the Channel design:

• The Bypass Channel bed would be approximately 800mm below the existing ground level, and would be lined with turf taken from areas of Luk Tei Tong Marsh that fall within the footprint of the proposed Channel. This area would be maintained as compensatory marshland habitat. So as to maintain the flood protection function of the channel, vegetation within the Channel would be maintained at a height of about 300mm.

• A low weir would be constructed at the downstream end of the Bypass Channel, serving to retain rainwater and some diverted floodwaters in the Channel. As the channel would be slightly lower than the existing ground level, and water within the channel would be retained, it is anticipated that habitats within the channel provide a more valuable wetland habitat than adjacent areas of Luk Tei Tong Marsh, where wetland vegetation is not particularly well established.

• The banks of the proposed Channel would be lined with rock-filled gabion, and topped with small (200mm high) earth bund. The gabion lining is required to stabilize the banks of the Channel, and the earth-bund would prevent surface water from surrounding areas of the marsh from draining into the Channel.

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7.8.20 The intention of re-using turf from the channel alignment is to provide suitable soil conditions for wetland habitats within the Bypass Channel. Additionally, roots and seeds of some plant species within the turf would speed up the establishment of wetland vegetation within the Channel. It should be noted though that parts of the Channel alignment are currently dominated by the weed Mikania micrantha, which would require removal prior to the construction phase. Reference should be made to Nature Conservation Practice Note No. 01/2003 for clearance of Mikania. A copy of the Practice note is included in the Appendices for ease of reference (Appendix 7.5 refers). 7.8.21 The construction of the LTT(2) by-pass channel is expected to take approximately 5 months. There is some concern that during this period, vegetation in sods of turf removed from the channel alignment would suffer some die-back before being replaced within the channel. To minimize potential die-back, it is recommended that turf removal (and channel construction) is limited to sections no more than 100m in length. The construction sequence would involve excavating the first 100m of the channel (at the downstream end of the alignment). Turf from this section would be moved to a temporary storage area. To minimize potential damage to this vegetation, the turf would not be stacked in layers during storage, and would be adequately watered for the duration of the storage period (i.e., 1-2 times daily). Following removal of the first 100m of turf, the second 100m of the channel would be excavated, and turf from this section immediately installed in the first excavated section of the channel. This process would be repeated until the last section of the channel is excavated. Turf removed from the first 100m section and stored during the construction would be used to re-vegetate this area. Even if some die-back occurs, it is expected that the roots and seed-bank within the turf will provide adequate material for the re-generation of vegetation following re-introduction into the LTT (2) Bypass Channel. Furthermore, vegetation from adjacent areas of the marsh would also be expected to re-colonise substrates within the Channel, which would provide a suitable growing medium for vegetation recorded from the marsh area. A programme would be established to monitor the ecology (including vegetation communities) of the LTT (2) Channel during the operation phase (section 7.10.4 refers). If there appears to be any problem with vegetative re-establishment, remedial measures (including the planting of riparian/emergent /aquatic vegetation) would be implemented (section 7.10.6 refers). 7.8.22 The new wetland area within the Bypass Channel would cover an area of approximately 0.6ha. Although this would be slightly smaller than the 0.8ha of existing habitat affected by the improvement works, wetlands provided within the channel alignment would be of higher ecological value than the habitats they would replace, providing adequate compensation for habitat loss. A full discussion of residual wetland habitat loss is presented in the later sections 7.9.2-7.9.3. 7.8.23 Temporary works areas adjacent to the Bypass Channel alignment would be re-instated with the planting of appropriate wetland plant species following the completion of construction works. No long-term impact to these areas are expected.

Woodland Habitat

7.8.24 Planting of trees and other vegetation along the banks of the newly created channels would provide compensation for unavoidable tree-felling and loss of small areas of open and secondary woodland habitat resulting from the proposed TTT and PNH River Channel and Ling Tsui Tau U-Channel works. Compensatory planting would make use of native plant species with flowers/fruits attractive to wildlife. Compensation in terms of woodland area and trees planted would be on at least a 1:1 ratio, covering an area of at least 0.13ha.

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7.9 Residual Environmental Impacts

7.9.1 With the proposed mitigation measures in place, residual impacts resulting from the proposed works would largely be limited to the loss of small areas of relatively low ecological value habitats. These would include, 0.2ha Inactive Wet Agriculture, 0.03ha Active Dry Agriculture, 0.36ha Developed Land/Wasteland and 0.03ha Tree/Orchard. Given the low ecological value and small areas of habitat affected, these impacts are considered minor and acceptable. 7.9.2 Habitat creation within the newly constructed LTT (2) River Bypass Channel is expected to fully compensate for the loss of ecological function resulting from the proposed works. However, even with habitat creation, the Project would result in the net loss of 0.2ha of habitat area within the Marsh, largely due to the necessity of providing support to the banks of the Channel. Based on criteria listed in the EIAO-TM, the scale of this residual impact is assessed in Table 7.8 below.

Table 7.8 – Evaluation of Residual Ecological Impact Due to Habitat Loss Within Luk Tei Tong Marsh

Impact Criteria Residual Impact Effects on health of biota or risk to life. No impact. Magnitude of impacts Small in relation to total area of Luk Tei Tong Marsh. Geographic extent of impacts Negligible. Duration and frequency of impacts Loss of habitat would be permanent. Size of the environment that may be effected. Small in the context of Luk Tei Tong Marsh as a whole (1.3% of the total marsh area). Reversibility of the impact Loss of marsh habitat would last for the duration of the bypass channel operation phase. If the channel were to be decommissioned, marsh habitat could be re-instated Ecological context Luk Tei Tong Marsh as a whole is considered of moderate-high ecological value, although the area subject to residual habitat loss is considered of lower ecological value, being relatively dry, disturbed, and dominated by the exotic weed Mikania micrantha. The 0.2ha of Marsh area lost does not form an important habitat for wetland species of conservation interest. International and regional importance Luk Tei Tong Marsh supports some wetland species of regional conservation concern, although the marsh is not recognised as being of regional or global conservation importance. Furthermore, the area subject to residual habitat loss is considered of lower ecological value, being relatively dry, disturbed, and dominated by the exotic weed Mikania micrantha. The 0.2ha of Marsh area lost does not form an important habitat for wetland species of conservation interest. Certainty regarding prediction of impact High degree of certainty regarding habitat loss. Residual Impact Very Minor

7.9.3 The loss of a small area (0.2ha) of Luk Tei Tong Marsh is considered a very minor residual impact. The affected area is small in the context of the Marsh as a whole, which covers an area of approximately 15ha. The permanently affected area of habitat therefore constitutes just 1.3% of the total marsh area. Furthermore, the compensatory wetland habitat provided by the

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Bypass Channel is expected to be of higher ecological value to wetland communities than the existing habitat it would replace. As described in section 7.8.19, the Channel has been designed to retain rainwater and some diverted floodwaters, thus providing a suitable habitat for the establishment of wetland vegetation. Therefore, although the proposed drainage improvement works would result in the small loss of habitat within the Marsh area, no substantial impact to the ecological function of Luk Tei Tong Marsh is anticipated. The loss of 0.2ha of habitat is therefore considered a very minor and acceptable residual impact. 7.9.4 While the scheduling of the proposed works close to the Disused Watchtowers would avoid the White-shouldered Starling breeding season, it is possible that other works under this Project (e.g., works further upstream of LTT (I) River) could cause disturbance to breeding Starlings. For this reason, a specific EM&A Programme to monitor Starling breeding activity and minimise potential impacts is recommended.

7.10 Environmental Monitoring and Audit Requirements

7.10.1 The proper implementation of mitigation measures recommended in Section 7.9 should be audited. 7.10.2 A specific monitoring programme of improved sections of PNH and LTT Rivers is recommended. The programme should provide data on the re-establishment of aquatic/riparian communities in the channels, and allow an assessment of the relative success of mitigation measures to be made. Baseline data should be collected on at least one occasion 2-3 months before the commencement of the construction phase, with monitoring conducted on a monthly basis during the construction phase, and every two months a year for 4 years after the completion of works. For the purposes of baseline, construction and operation phase monitoring, the improved sections of the PNH and LTT rivers should be divided into 50m long sections, and data collected from each of the sections should include the following parameters: ♣ Water quality (e.g., dissolved oxygen, pH, conductivity, salinity, BOD, suspended sediments, ammonia, nitrate and phosphate concentrations); ♣ Sediment characteristics; ♣ Water flow; ♣ Avifauna species and densities; ♣ Aquatic macroinvertebrate community species composition and abundance; ♣ Fish community species composition and abundance; ♣ Adult odonate community species composition and abundance; and ♣ Aquatic, emergent and riparian vegetation community species composition and abundance. 7.10.3 Reports on the findings of each monitoring trip should be submitted to Agriculture, Fisheries and Conservation Department (AFCD) and the Environmental Protection Department (EPD) for review. A final report summarising the monitoring results over the entire monitoring period should be prepared to serve as a reference for future projects of this kind. Monitoring should be conducted by a qualified ecologist(s) with over 6 years relevant experience.

7.10.4 Monitoring of the LTT (2) Bypass Channel would be required to confirm that the proposed Channel design has provided suitable compensation for impacts to Luk Tei Tong Marsh. It is

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suggested that ecological monitoring of habitats within the Channel should be undertaken for a period of at least 4 years. Data collected should include the following key parameters: ♣ Water quality (e.g., dissolved oxygen, pH, conductivity, salinity, BOD, suspended sediments, ammonia, nitrate and phosphate concentrations); ♣ Sediment characteristics; ♣ Water depth and flow; ♣ Avifauna species and densities; ♣ Aquatic macroinvertebrate community species composition and abundance; ♣ Fish community species composition and abundance; ♣ Herpetofauna community species composition and abundance; ♣ Adult odonate community species composition and abundance; and ♣ Aquatic, emergent and riparian vegetation community species composition and abundance. 7.10.5 To provide baseline data, it is suggested that the same parameters are measured along a strip of existing marsh habitat adjacent to the Channel alignment. A comparison of species diversity and densities along the Bypass Channel alignment and at the reference site would allow the effectiveness of habitat creation to be assessed. Monitoring of both the Channel and Reference Site should be conducted 6 times a year for 4 years after the completion of works. For the purposes of monitoring, the Channel and Reference site should be divided into 50m long sections, with the majority of biotic and abiotic parameters listed in section 7.10.4 monitored in each of the 50m sections. However, water quality (e.g., dissolved oxygen, pH, conductivity, salinity, BOD, suspended sediments, ammonia, nitrate and phosphate concentrations) would be measured at four locations along the channel and reference site alignments only, as there would be little expected variation in water quality along the length of the channel. Reports on the findings of each monitoring trip should be submitted to AFCD and EPD for review. A final report summarising the results of monitoring over 4 years should be prepared to serve as a reference for future projects of this kind. Monitoring should be conducted by a qualified ecologist(s) with over 6 years relevant experience. 7.10.6 The newly constructed PNH and LTT River Channels, and LTT (2) Bypass Channel are expected to provide a similar habitat to the habitats they would replace. It is therefore anticipated that wildlife found in the existing rivers and marsh would successfully re-colonise the new channels. However, if the post-construction phase monitoring demonstrates that re-colonisation is unsuccessful the following contingency plan should be implemented:

• Baseline/reference data should be compared with post-construction phase data. Any substantial differences in habitat characteristics (e.g., water quality, aquatic/emergent vegetation) should be noted.

• The potential cause of differences between baseline/reference and post-construction phase habitat characteristics (e.g., changes in water depth, sediment characteristics) should be identified.

• Measures to further rehabilitate the habitat characteristics of the channels should be implemented. Such measures could include:

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− Minor re-profiling of the channel bed(s) could be implemented to increase micro-habitat diversity within the channels. By excavating small areas of the bed, areas of slow flowing water would be created within river habitats, and small pools of very slow-flowing or standing water would be created within the marsh.

− Increasing heterogeneity of substratum would again increase micro-habitat diversity: providing substrates of different sizes would provide niches for organisms preferring small sediments (e.g., burrowing dragonfly larvae) and larger cobbles/boulders (e.g., Heptageniid mayfly nymphs).

− Planting of suitable aquatic, emergent and riparian vegetation could serve to increase vegetative cover.

− Management of water levels within the LTT (2) River Bypass Channel could be implemented by modifying the height of the weirs at either end of the Channel; thus optimizing conditions for wetland habitat establishment within the Channel.

• Further monitoring of abiotic and biotic parameters should be conducted to determine the relative success of the contingency habitat rehabilitation measures.

7.10.7 A specific monitoring programme for the White-shouldered Starlings is recommended. A qualified ecologist with over 6 years relevant experience should conduct the monitoring. Monthly baseline surveys of the Disused Watchtowers should be undertaken in the wet season prior to the commencement of construction phase activities. The aim of baseline surveys should be to establish whether or not any breeding Starlings are still present. If breeding activities are identified, the number of breeding pairs, the success of breeding and responses to any disturbance should be recorded. During the construction phase, monthly surveys of the Watchtowers are recommended. Information should be collected on behaviour, breeding activity, and any response to disturbance. The source of any disturbance impacts should be identified. A simple Event and Action Plan is recommended in Table 7.9.

Table 7.9 Monitoring White-shouldered Starlings: of Event and Action Plan

Event Action Environmental Manager Contractor Identification of disturbance 1. Increase frequency of monitoring to 1. Check all construction actions and to breeding twice weekly. working methods. White-shouldered Starlings 2. Notify Site Engineer 2. Submit proposals for remedial action to prevent abandonment of the breeding site. 3. Review construction activities of 3. Implement remedial action. pervious week. 4. Identify any changes in construction 4. Liaise with EM regarding activities in previous week. effectiveness of remedial actions. 5. Discuss remedial actions with Site Engineer.

References

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Memoirs of Hong Kong Natural History Society 22:183-209.

Agriculture, Fisheries and Conservation Department (2002) Checklist of Hong Kong Plants 7th Edition 407p.

Bascombe, M.J., Johnston, G. & Bascombe, F.S. (1999) The Butterflies of Hong Kong. Academic Press, London: 422p.

Carey, G.J., Chalmers, M.L., Diskin, D.A., Kennerley, P.R., Leader, P.J., Leven, M.R., Lewthwaite, R.W., Melville, D.S., Turnbull, M., and Young, L. (2001): The Avifauna of Hong Kong. Hong Kong Bird Watching Society, Hong Kong.

Chan, B.P.L. (2001) Sustainability and Biodiversity: the Impact, Alternative Design and Prospects for Restoration of Channelized Lowland Streams in Hong Kong: Unpublished Ph.D. thesis, University of Hong Kong

Dudgeon, D. (1995) Environmental impacts of increased sediment loads caused by channelization: A case study of biomonitoring in a small river in Hong Kong. Asian J. of Env. Manage. 3: 69-77.

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