History of Mapping Hong Kong Part 12 – Post War Geological Maps

September 12, 2024 Tymon General

Tymon Mellor: Between 1923 and 1933, four Canadian geologists mapped and documented the territory’s geology. This resulted in the first geological map being published in 1936, along with a memoir published much later in 1952. In the post war environment, the high population growth and economic development required new and extensive infrastructure, in turn requiring a better understanding of the territory’s geology. However, the Colonial government was short of funds and technical skills, and so they needed to look to London for support.

Military Needs

While war was raging in the Pacific, the British military was planning to return to Southern China. The Geographical Section, General Staff (GSGS) formed the Inter-Service Topographical Department in May 1940 with the responsibility to provide topographic intelligence for the British forces^[1]. Within the organisation of over 300 staff, the geological section was founded in November 1943 by two geologists, Tom Phemister and Jack Farrington from Canada and Australia respectively. By the summer of 1945, the team had grown to 12, producing reports and specialist geotechnical maps. The military had identified that existing geological maps were of little use without specialist interpretation. Thus, the team was tasked with the development of geological maps focused on military needs relating to construction materials, quarrying, airfield construction etc., all the things you would need when planning an extensive military campaign.

Using available information, the team produced several maps for Hong Kong and the Canton area, the first being a simplified geology of the territory dividing the rocks into five categories and provided details of the category characteristics. Two maps were produced, one for Hong Kong and one for the wider region.

Hong-Kong Canton Area Simplified Geology GSGS Misc 192A (1944)

A second map, covered the same Hong Kong and Canton area, but identified land suitable for rapid airfield construction. The colours providing a simple guide to the suitability of the ground. Lighter shades equating to good conditions, while darker shade equated to bad.

Airfield Construction colour Scheme (1944)

Hong-Kong Canton Area suitability for Airfield Construction GSGS (1944)

With the end of the Pacific War in August 1945, the new geological maps were never used in earnest. However, the benefit of maps to indicate variations in features or categories had been demonstrated, and which would go on to be extensively adopted for many applications.

Need for a New Map

During the initial post war boom, the government was focussed on re-construction and providing the basic needs for the growing population. While there was a general recognition that a new geological survey would be beneficial, no government department had the funds to undertake the work.

In 1963 the Government commissioned Hunting Survey Ltd to undertake a detailed aerial survey of the territory. With the boom in construction, the quarrying industry was running out of capacity, prompting the Director of the Public Works Department, J J Robson to ask Hunting if the new aerial photographs could be used to identify new quarry sites in the Kowloon foothills. As Robson noted^[2]:

“The results were most impressive as even from the rather crude source of information they were able not only to locate potential quarry sites but also express an opinion on the nature of the rock, overburden, etc”

It is probably no coincidence that the existing quarries at Anderson Road were developed to become the largest supplier of aggregate to Kowloon.

Based on the discussion with Robson, in the autumn of 1963, a sister company, Hunting Technical Services Ltd provided a technical proposal to the Government for geological services^[3]. The proposal included:

preparation of a geological map identifying the rock formations, mineral veins and cross sections;
preparation of a geotechnical map for use by engineers showing rock and soils; and
preparation of a hydrogeological map identifying areas of relative permeability and water infiltration.

The maps would be prepared at 1:25,000 with a higher scale of 1:10,000 in selected areas, for a total cost of around $1 million. Robson could not justify this cost just for the Public Works Department and following internal discussion, no other department would provide financial support.

Local Talent

While the Government was trying to find funds for a new survey, Professor S G Davis at Hong Kong University continued to research and publish reports on mineral deposits while B P Ruxton, a new lecturer at the University pursued the broader geological field, publishing several review papers on the matter. Ruxton was critical of the previous work undertaken by the Canadian geologist before the war and proposed a new stratigraphic nomenclature along with a sketch map at 1:250,000 scale in a 1956 paper, The Geology of Hong Kong^[4].

The Geology of Hong Kong, Ruxton, 1956

Return of the Geologist

In the summer of 1965, the Colonial Government became aware that the Overseas Geological Survey was to be merged with the Geological Survey of Great Britain under the Department of Scientific and Industrial Research. Part of the new remit included; “provision should be made for extended visits of experts overseas to help inform local Governments of facilities available in the United Kingdom for technical assistance”. The Governor requested assistance to undertake a preliminary review into the possibilities of a geological survey and recommendations into how to implement the survey^[5].

By chance, the Director of the Overseas Geological Surveys, Dr S H Shaw was planning a visit to Tokyo in November, 1965 for a conference. He arranged to stop in Hong Kong for a few days on his return to be briefed on the situation and assess the scale of the work. Landing on the 21 November, he met senior members of the Government, was taken on a helicopter tour, visiting Hong Kong University and had working meetings with the Public Works Department before departing on the 26 November. The conclusion from the visit was that a representative from the Overseas Geological Survey would be appointed to the Government for around 12 months to provide technical advice on geological matters^[6].

This was not what the government was looking for, as they wanted a geologist to prepare a map of the territory. During 1966 negotiations continued with the Overseas Geological Survey and subsequently in January 1967, Dr E A Stephen and Dr P M Allen of the Overseas Division of the Institute of Geological Sciences arrived in the territory to lead a small team to prepare a new map and report on the geology of the territory.

Geological Survey Report 1971

Over the next 26 months the group mapped the geology, studied aerial photographs to identify faulting and other features and sampling stream sediments to support a geochemical survey. The team also put considerable effort into establishing the geomorphology or study of the landscape to understand the processes that had occurred. Hong Kong was considered to be a drowned portion of a larger mountain range as a result of rising sea levels, but there was much debate surrounding when and by how much the water had risen.

The geochemical survey was used to identified trace elements indicating possible areas of economic mineral deposits. Six areas were identified for further detailed analysis and possible prospecting. A review by government departments was not positive, as the majority of the areas were in sensitive water catchment zones or private agricultural land. There was no enthusiasm to pursue the commercial opportunity.

Identified Areas of Mineral Interest

The survey resulted in a new geological map, published in 1972 on two sheets at a scale of 1:50,000. This was a significant improvement on the previous maps as not only did it have more details but included geological structure and the work undertaken by Ruxton.

Geological Map of Hong Kong (DOS1184A 1972)

Disaster Strikes

By the early 1980s the geological map was considered to be out-dated and not in sufficient detail for use by the local engineering community. Rapid development, major infrastructure projects, and particularly the construction of buildings on hillsides required a good understand of the ground conditions. Landslides and the growing number of manmade slopes were becoming a greater risk, or as a government source noted in 1981, “Since a lot of buildings were built at midslopes and foothills where only scrubs and trees were found in 1965 when the existing geological map was made, there is a need to update the information”^[7].

The risk became very real within a few months. On the 18 June 1972, after three days of heavy rain and multiple landslides throughout the territory, two major landslides occurred of different sides of the harbour. In Kowloon a fill slope supporting Hiu Kwong Street of Sau Mau Ping collapsed releasing tonnes of debris, destroying 78 squatter huts of the resettlement area and killing 71 people.

On Hong Kong Island, a landslide happened on the natural slope above Po Shan Road in the Mid-Levels. The landslide debris struck the 12-storey Kotewall Court and a six-storey house, causing both to collapse and resulting in 67 fatalities.

These two incidents were just the culmination of early landslides but with relatively few fatalities. In most cases the slips were attributed to the unprecedented rainfall. However, local construction works allowed water to infiltrate faster which destabilised the slopes and reducing the safety of the slopes.

The recommendations of the enquiry into the incidents^[8] published in November 1972 concluded, “We are of the opinion that the risk of landslips in Hong Kong arises more from deficiencies in supervision and control of works than from deficiencies in design”.

The recommended actions included: regular inspections by experienced engineers of risk areas, and, the setting up of a new section of the Public Works Department to carry out:

geological and topographical studies of urban areas to identify where landslips may occur;
comprehensive investigation of landscape risk areas identified;
inspection of potential risk areas;
identify measures to improve hillside stability;
review the site investigations and foundation proposals for developments in risk areas;
powers to ensure all excavations in risk areas are protected and completed without delay;
review foundation designs of existing structures in risk areas; and
patrol potential landslip areas during periods of intense rainfall and advise the immediate evacuation of areas in danger.

In response to the report, the PWD set up the Geotechnical Control Office, employing ten geologists by 1980 primarily engaged in slope stability work^[9]. Within the group, a small team was focused on geotechnical studies to support development planning, using aerial photographs and extensive field mapping. They had noted that the 1972 geological map lacked sufficient detail for engineering design and errors had been identified. A new map was needed.

Hong Kong Geological Survey

On the 5^th May 1982 the Hong Kong Geological Survey (HKGS) team was created within the Engineering Development Department^[10], and its task was to carry out a detailed geological survey of the territory to assist with land planning. It was also to establish itself as the knowledge centre for geotechnical information and understanding, providing advice to both government, public and private parties.

The team was to produce a new set of maps of the territory’s geology at a scale of 1:20,000, comprising 16 sheets and six memoirs in total. The first sheet and associated memoir covered the Shatin area, no doubt in support of the new town development.

Initially, the small team was led by Dr R Addison, a geological mapping consultant from the Overseas Division of the British Geological Survey (BGS). There were four mapping geologists, and six technical and support staff. Another mapping geologist joined the HKGS in late 1984 to be responsible principally for mapping of superﬁcial deposits in the offshore areas and undertaking weathering studies. Dr A D Burnett led the HKGS team with the geological survey section being led by Mr R. S. Arthurton. The team spent 1983-84 mapping the Shatin area for the new geological map. The team continued to grow, bringing specialist resources from the BGS for particular issues and recruiting locally trained staff where possible. New maps and memoirs were published on a regular basis with the last volume covering Lantau published in December 1995.

The Hong Kong Geological Survey in January 1994

By now the team was part of the Geotechnical Engineering Office of the Civil Engineering and Development Department and a review was undertaken on its future role. Its scope of activities was expanded to include geological mapping of major landslides, tunnel geology, regional geochemical surveys, concrete petrography and geological input into land use planning. In 2003 the team embarked on a programme to update the 1:20,000 maps and release them in digital form between 2005 and 2015 with a staff of five geologists and four technical support staff.

In addition to the 1:20,000 map series, the HKGS also produced 23 geological sheets at 1:5,000 for strategic development areas. These include areas around Yuen Long underlain by marble or marble related rocks that present challenges for foundation design^[11].

From the initial request for a geological map in 1920 to the most recent digital versions, the level of knowledge and information has greatly improved and has been refined. Hong Kong now has some of the most advanced and sophisticated geological maps in the world, driven by a need to help the planners, designers and builders to address the complex and challenging geology necessary to support world leading infrastructure.

Development of the Geological Map of Hong Kong

Sources

Wartime Geotechnical Maps, Ted Rose, The Geological Society ↑
Geological Survey of the Colony, Director of Public Works, 8 Nov 1963 ↑
Proposal for Geological Services, Hong Kong, 4 Oct 1963, HKRS 934-3-39 ↑
The Geology of Hong Kong, Bryan P Ruxton, Quarterly Journal of the Geological Society 31 Oct 1956 ↑
Savingram Geological Survey of Hong Kong, 24 Aug 1965, HKRS 934-3-39 ↑
Memo Director of Public Works, 1 Dec 1965, HKRS 934-3-39 ↑
Govt to decide soon on new geological chart, SCMP 23 Sep 1981 ↑
Final Report of the Commission of Inquiry into the Rainstorm Disasters 1972, GEO Report No 229 ↑
Plans in hand for a new geological survey, SCMP, 29 Nov 1980 ↑
Hong Kong Geological Survey, R J Sewell, Episodes, Dec 2007 ↑
The Work of the Hong Kong Geological Survey, R J Sewell, KC Ng, CW Lee and CF Wong, Conference Paper, Aug 2008 ↑

This article was first posted on 12th September 2024.

History of Mapping Hong Kong Part 12 – Post War Geological Maps

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