SAJC Cluster 4 GI (Fluvial Flood Management Qn + notes)

SAJC/Geography/Fieldwork_Exercise_2025 Page 1 St Andrew’s Junior College H2 Geography Cluster 4: Fieldwork Topics in the syllabus: Fluvial flood risk and strategies to mitigate it (Cluster 2) Area chosen: Bishan Ang Mo Kio Park (BAMK Park) Hypothesis: Places near the Kallang River in BAMK Park have higher flood risk than places far from the riverbank. Geographical question: Does places near the Kallang River in BAMK Park have higher flood risk than places far from the riverbank? Develop a plan: • establishes the primary and secondary data needed to examine the question/hypothesis posed • identifies appropriate methods to determine sample size, select sample and collect data • ensures accuracy and reliability of data collected • addresses possible issues related to research ethics and the limitations imposed by resources • minimises potential risks in undertaking fieldwork. Craft Geographical Question or Hypothesis Students should be able to craft geographical questions/hypotheses based on geographical issues or phenomenon that are: • at a suitable scale • researchable or measurable • clearly defined

SAJC/Geography/Fieldwork_Exercise_2025 Page 2 • How does flood risk differ with distance from the Kallang River in BAMK Park? (Swamp Tea Tree and Aramsa) • How does flood risk differ with land use along the Kallang River in BAMK Park? (Students may opt to study Swamp Tea Tree and Aramsa/241 HDB) • How does flood risk differ with urban function along the Kallang River in BAMK Park? (Aramsa and 241 HDB) Flood Risk Index: Indicator Rating for Site A Rating for Site B Severity of Impact (1: Highly Severe; 5: Not Severe) Distance from river channel Elevation above river channel Land Use Human Flow River Efficiency (1: Low river efficiency; 5: High river efficiency) Hydraulic Radius Potential for OLF to Take Place (1: High potential for OLF; 5: Low Potential for OLF) Ground Cover Infiltration Rate Effectiveness of Mitigating Strategies (1: Ineffective; 5: effective) Hard Engineering Measures Soft Engineering Measures Average Rating: Data Collection Methods: Indicator Data Collection Method Severity of Impact (1: Highly Severe; 5: Not Severe) Distance from river channel Google Map Elevation above river channel Google Map Land Use Observation Human Flow Pedestrian Count River Efficiency (1: Low river efficiency; High river efficiency) Hydraulic Radius Measurement Potential for OLF to Take Place (1: High potential for OLF; 5: Low Potential for OLF) Ground Cover / Landuse pattern Observation Infiltration Rate Measurement Effectiveness of Mitigating Strategies (1: Ineffective; 5: effective) Hard Engineering Measures Observation Soft Engineering Measures Observation

SAJC/Geography/Fieldwork_Exercise_2025 Page 3 To measure infiltration rate, follow the steps below: a) Based on the considerations above, select two different areas at different distance from the Kallang River. ➢At different distance from the river: near and far ➢ Different land use: vegetated (permeable), impermeable surface ➢ Accessible For example: • Site A - Swamp Tea Tree (near the river, vegetated) • Site B - Aramsa/241 HDB (far from the river, building) b) Sink/hammer a bottomless round tube/container (15cm), about 3-5 cm, into the ground of one area you have selected. c) Place a ruler vertically inside the tube/container to record fall in water level. d) Fill the tube/container with water, perhaps to about 10 cm in height or even to the brim. e) Measure and record the drop in the water level after 5 minutes. f) Top up the water and record the drop in the water level after another 5 minutes. g) Repeat step f. Note that you should record the drop in water level for at least 3 successive periods of 5 minutes. It would be best to continue the experiment until infiltration appears to be at a constant rate (this would be the steady-state infiltration capacity of the soil). h) Record your results in the tables that follow. i) Repeat steps b to h for the ground of the other area (Sites B) you have selected. Example Suppose we fill the tube/container to the brim. Drop in water level after 5 minutes = x cm  Infiltration rate = x/5 cm per min or x/300 cm per s You are required to pick two sites to measure infiltration rate: • Site A - Swamp Tea Tree (near the river, vegetated) • Site B - Aramsa/241 HDB (far from the river, building) However, do take note of site chosen and take pictures of the site for reference. Record the drop in the water level after 5 minutes Above ground Ruler

SAJC/Geography/Fieldwork_Exercise_2025 Page 4 Description of Selected Site A: _________________________________________________ ___________________________________________________________________________ Attempt 1 Attempt 2 Attempt 3 Drop in water level after 5 minutes (cm) 2cm 1.8cm 1.6cm Average Infiltration rate Infiltration rate (cm/min) 2cm/5= 0.4cm/min 1.8cm/5= 0.36cm/min 1.6cm/5= 0.32cm/min 1.08cm/3= 0.36cm/min Description of Selected Site B: _________________________________________________ ___________________________________________________________________________ Attempt 1 Attempt 2 Attempt 3 Drop in water level after 5 minutes (cm) Average Infiltration rate Infiltration rate To improve accuracy of measuring infiltration rate: Use a double ring infiltrometer – you can also measure infiltration rates using a double ring infiltrometer, which can yield reliable and accurate results. Drive the infiltrometer 15-20 cm into the soil. Be sure the rings are level. Cover the soil surface in the inner cylinder with a perforated metal plate, in order to dissipate the force of applied water and distribute water uniformly inside the ring. Add water in both rings. Measure the amount of water infiltrated after every fixed interval, such as 15 minutes, for at least three successive periods. Ensure that the water in both the inner and outer cylinders is topped up after each interval. Note that the measurement is to be taken in the inner cylinder; the outer cylinder is used only as a tool to ensure that water from the inner cylinder will flow downwards and not laterally.

SAJC/Geography/Fieldwork_Exercise_2025 Page 5 Fluvial flood risk and strategies to mitigate it To determine flood risk, we need to measure 1) river discharge and 2) river efficiency 1) Measuring River Discharge (i.e. cross sectional areas and velocity) of the channel Many factors can influence flood risks. These include both natural (e.g. climate, geology, gradient) and anthropogenic factors (types of land use). Essentially, flood occurs when the channel exceeds its bankful discharge. Hence, it would be useful to measure the discharge of the river channel. Discharge refers to the volume of water that passes through a given cross section per unit time, usually measured in cubic meters per second (m/s). Discharge (Q) = Cross Sectional Area (A) x Velocity (V). Stage 2: Data Collection 1.1 Measuring the cross sectional area of the channel. Cross Sectional Area (A) = Width (W) x Depth (D) Measuring the width (W) of the channel: Follow the steps below: a) Requires at least two persons. b) Identify a section of the channel that you want to measure. c) One person stands with the measuring tape on one bank of the channel, where the water touches the bank. The other person walk across the river pulling the measuring tape across the water surface to the other bank of the channel. d) Record the length of the width in centimetres. A B

SAJC/Geography/Fieldwork_Exercise_2025 Page 6 Measuring the depth (D) of the channel Follow the steps below: a) Requires at least 3 persons. b) Depending on the width of the c