2025 ACJC Prelims P2 Answers

© ACJC 2025 [Turn over READ THESE INSTRUCTIONS FIRST You should follow the instructions on the cover sheet. If you need additional answer paper, ask the invigilator. Write your index number and name on the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer Question 1 in Section A. Answer Question 2 in Section B. Answer one question in Section C. Start your answer to each question on a fresh sheet of answer paper. At the end of the examination, your answers should be separated and securely fastened into 2 bundles. Attach a cover sheet on top of bundle 2. • Bundle 1: Answers to Question 1. Name and index number to be clearly indicated on the first page of the answers. • Bundle 2: Cover sheet and answers to Question 2 and Question 3 or 4. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 5 printed pages and 1 blank page. ANGLO-CHINESE JUNIOR COLLEGE JC2 Preliminary Examination Higher 2 GEOGRAPHY 9173/02 Paper 2 16 September 2025 3 hours Additional Materials: Insert Cover Sheet Answer Paper

2 © ACJC 2025 9173/02/JC2 Preliminary Examination Answer Questions 1 and 2 and EITHER Question 3 OR Question 4 Section A Cluster 4 Fieldwork 1 There are plans to turn the coastal mangrove area around the Sungai Mandai Besar River in northern Singapore into a nature park that will be named the Mandai Mangrove & Mudflat Nature Park. A group of five students wanted to assess the flood risk around the Sungai Mandai Besar River. The river is concretised into a canal for most of its course except for the short stretch at the river mouth. The hypothesis the students chose: ‘Fluvial flood risk is lower near the river mouth than around the canalised parts of the Sungai Mandai Besar River.’ To assess the flood risk of the areas surrounding the river, the students collected data on infiltration rates and selected river variables. They collected data on a week day in December from 10 am to 4 pm. At each site, two students worked on the infiltration test, while three worked on collecting data on selected river variables. All five of them worked at Site A first. They were only able to start work at Site B after the thunderstorm ended at 3 pm. They collected infiltration data around Site B, and only the river velocity data at Site B. The equipment that the students used for their field investigation included: • A single-ring infiltrometer made of white plastic tubing with a diameter of 10 cm and a height of 30 cm • Two brightly marked half-filled plastic mineral water bottles as the velocity-floats • Two stop watches • A pail to fetch water from the river for the infiltration test For the infiltration test, the students chose two locations at each site . At Site A, the infiltration test was taken at the grassy patch next to the river bank (indicated as A1 in Resource 1) and on forested land (indicated as A2). At Site B, two infiltration sites were chosen [indicated as B1 (concrete surface) and B2 (muddy river banks) in Resource 1]. Resource 1 is a land use map of the area adjacent to the Sungai Mandai Besar River, showing Sites A and B and the four infiltration sites A1, A2, B1 and B2 . Resource 2 shows the photographs of Sites A and B. Resource 3 shows the infiltration rates at each of the four sites around the Sungai Mandai Besar River. Resource 4 shows the findings of the investigation at Sites A and B

3 © ACJC 2025 9173/02/JC2 Preliminary Examination [Turn over (a) Explain whether the hypothesis chosen is suitable for their investigation of flood risk around the Sungai Mandai Besar River. [4] Award 1 mark for each explanation of the suitability of the hypothesis for the investigation of flood risk around Sungai Mandai Besar River. Award a maximum of 1 additional mark for further development of each explanation. Possible responses include: • Scale: The hypothesis is suitable because the area of study around the Sungai Mandai Besar River is small in scale and manageable for the group of five student investigators [1 mark]. The distance between Sites A and B is not more than 300 metres making it easily accessible for the students. [1 additional mark] • Accessibility: The sites (A and B) are safe and accessible, with clear contrasts in channel form and land use shown in the resources, allowing data to be easily collected [1 mark] When the river at Site B is too wide and there is no overhead bridge, there was a ready source of data from secondary data derived from an environmental assessment report. [1 additional mark] • Equipment: The measurements needed, such as infiltration rates and cross - sectional profiles, can be obtained using standard fieldwork equipment and available manpower [1 mark]. • However, the hypothesis is limited as it does not consider wider influences on flood risk such as upstream rainfall inputs or tidal effects, which are beyond the study site [1 mark]. Examiner’s comments

4 © ACJC 2025 9173/02/JC2 Preliminary Examination (b) With reference to Resources 1 and 2, describe how the students could reduce the impacts of their investigation at the two sites A and B. [6] Award 1 mark for each suggestion on how the students could reduce the impact of their investigation at the two sites. Award 1 mark for each explanation on how the students could reduce the impact of their investigation, to a maximum of 6 marks. Award a maximum of 1 additional mark for further development of each explanation, where applicable. Possible response: At Site A (channelised canal with concrete banks): • Students could avoid obstructing the narrow footpath and at the overhead bridge and ensure equipment does not block movement along the canal [1 mark]. • Avoid throwing materials or litter into the concrete channel to prevent pollution, and bagging the thrash would be the right thing to do [1 mark]. • Avoid making loud sounds to avoid causing alarm or disturbance to the wildlife in the forests around the bridge location [1 mark]. At Site B (natural channel with clay and silt banks in swamp/mudflat setting): • Students should keep to existing paths and avoid trampling swamp and mudflat vegetation to minimise habitat disturbance [1 mark]. • To prevent excessive disturbance to the soft and weak sediment, trampling may be reduce if a small plank can be placed gently on the surface and one investigator will be using the plank as the stepping point to sampling groups to reduce pressure on any single part of the site and minimise erosion of the soft riverbanks [1 additional mark]. • For infiltration tests refill holes after measurements so the ground surface is restored [1 mark]. • Since Site B is located at the natural swamp forest, it is necessary to keep noise to the minimum to prevent disturbing or alarming the wildlife [1 mark]. For both sites, a plastic bottle velocity float is used. As plastic is not biodegrable, using an orange would be more suitable since it is biodegrable, and knowing that the float cannot be retrieve without compromising safety. Try to retrieve the plastic bottle using a net on a pole. Examiner’s comments:

5 © ACJC 2025 9173/02/JC2 Preliminary Examination [Turn over (c) Explain how the students could overcome potential risks when they conduct their fieldwork i