Kai Tak River Improvement Works (Wong Tai Sin Section), Hong Kong

The brief was to implement essential flood prevention works to an existing ugly and polluted drainage channel - Kai Tak Nullah – running though the dense urban area of Kowloon City and in doing so, convert the channel into a green and attractive urban river corridor that creates an asset for the local community.

Alexander Duggie was the URBIS landscape team leader, leading the landscape design from start to finish.

A 2-stage public consultation was undertaken in 2010-11, firstly to determine the public’s ideas and aspirations for the project and secondly to present the team’s design proposals responding to those ideas for the public’s further review and comment. The key public aspirations were to:
- improve the drainage capacity;
- create a landscape within the river that resembles a natural river;
- create more greening;
- preserve and incorporate the existing granite parapet walls.

Local schools and local artists were also invited to take part in activities and events that explored and reinforced the connection between the ‘river’ and the community.

The overall Design Vision for the project is to convert Kai Tak Nullah into an attractive urban green river corridor – Kai Tak River (KTR) – and to service community needs whilst meeting the need for flood protection. Drainage Services Department developed a multi-pronged strategic plan to prevent future flooding and improve the channel hydraulics by capturing illegal foul drains before they entered the channel; removing unsightly utility pipes and ducts that criss-crossed the channel, and piping treated grey water from Tolo Harbour to the head of the river so as to provide a constant flow of river water in all seasons.

To support the Design Vision, the landscape design concept promotes a ‘storyline’ in which the ancient natural KTR has been gradually encroached upon by urban development, necessitating the construction of man-made walls on top of the natural river bedrock, both to contain the river and prevent flooding of the adjacent urban areas. Thus for any given section through the River channel, the lower portion is ‘natural’ and the upper portion is man-made.

Sustainability is promoted by:
- preservation of all existing Ficus trees along the channel edge - they provide a beautiful greening effect, cooling shade and an important habitat for wildlife;
- preservation of the existing old granite parapet walls;
- use of locally/regionally quarried granite for the channel wall cladding, to match the retained parapet walls;
- use of recycled and permeable concrete block paving in adjacent public footpath improvements so as to promote SUDS;
- use of Tolo Harbour Effluent Export Scheme grey water to maintain minimum river flow during dry winter season;
- use of native plants to attract insects and birds and promote biodiversity;
- careful design of rockwork and boulders along the river edge to create swirls, eddies and calmer water for fish to rest;
- use of river bed planting of emergent plant species (with roots secured in submerged ‘grasscrete’ panels) to provide potential habitat for young fish and amphibians.

Key problems/challenges and their solutions included:
- The dense urban context meant that the channel footprint could not be widened, hence all critical hydraulic improvements had to be achieved by manipulating the channel cross-sections.
- Landscape within the channel must withstand vastly different seasonal conditions and occasionally strong river currents. Species are selected that can survive dry conditions with occasional inundation during summer floodwaters. Hollow artificial rock enables plant roots to establish within soil pockets protected from erosion.

KTR is revitalised as Hong Kong’s first urban green river corridor, serving as a major drainage channel, a visual resource for public enjoyment and an ecological resource bringing nature back into the city.