Cover lesson · Geography · Year 8 · Intermediate
LNF: Literacy → Reading → Understanding, response and analysis
Also assessed, DCF: Data and computational thinking → Data and information literacy
Name: Class: Date:
What this practises: distinguishing fact from opinion in witness statements and synthesising multiple texts into a balanced 150-word enquiry report (LNF literacy: understanding, response and analysis), alongside reading storm hydrograph data, calculating lag time, and checking claims against river gauge numbers (DCF: data and information literacy).
Board: open the supply teacher presentation (/cover-lesson-resources/presentations/synthesising-witness-accounts-and-river-data-for-a-flood-enquiry.html) for board slides, countdown timers and a spoken script.
Print: this worksheet, one per pupil, and the stimulus sheet “The Pont y Glyn flood enquiry: storm hydrograph, rainfall data and witness accounts”, one between two. No computers are needed.
Run: 5 min settling starter · 5 min brief and key vocabulary · 10 min Step 1, reading the storm hydrograph and calculating lag time · 10 min Step 2, distinguishing fact from opinion and testing witness claims · 12 min Step 3 and Step 4, explaining impermeable surfaces and writing the 150-word community council summary · 5 min partner/self check against success criteria · 3 min plenary quick-check. Total 50 minutes.
Collect: this worksheet. Quick checks: total rainfall = 48 mm; peak rainfall = 18 mm at 14:00; peak discharge = 52.0 cumecs at 17:30; lag time = 3 hours 30 minutes (3.5 hours); river was above 40.0 cumecs bankfull from 16:00 to 19:00 (3 hours); Witness B (Mark Evans) is wrong (rain was 48 mm, not 100 mm, and discharge at 14:30 was only 18.0 cumecs, not flooding); compared with 2019, lag time fell by 1.5 hours (5.0 h to 3.5 h) and peak discharge rose by 14.0 cumecs (38.0 to 52.0 cumecs).
On 14 October 2026, the Afon Glyn burst its banks and flooded High Street in Pont y Glyn. Three residents have sent witness statements to Pont y Glyn Community Council: a bakery owner blaming a new retail park car park, the retail park manager blaming a “100 mm monsoon”, and a retired hydrologist. Using the stimulus sheet, you will calculate the storm’s lag time, test each witness’s claims against the river gauge table, explain how impermeable tarmac changed the hydrograph, and write a balanced 150-word enquiry summary.
Use Section 1 of the stimulus sheet.
(a) Complete the summary table for the 14 October 2026 storm at Pont y Glyn Bridge.
| Hydrograph measurement | Value and unit (use 24-hour clock times) |
|---|---|
| Total storm rainfall between 12:00 and 16:00 (mm) | |
| Time and amount of peak rainfall (mm) | |
| Time and amount of peak river discharge (cumecs) | |
| Lag time (Time of peak discharge − Time of peak rainfall) | |
| Time the river first reached 40.0 cumecs bankfull and time it dropped back to 40.0 cumecs | |
| Total number of hours the river stayed at or above 40.0 cumecs (flood duration) |
(b) How many cumecs above the 40.0 cumecs bankfull threshold was the river at its 17:30 peak?
Read the three witness statements in Section 2 of the stimulus sheet and compare them with the gauge table in Section 1.
(a) Complete the witness audit table below.
| Witness | One factual claim they make (times or numbers) | One opinion or biased phrase in their statement | Does the river gauge data support their factual claim? (Quote numbers) |
|---|---|---|---|
| Witness A: Siân Parry (Bakery owner) |
Water poured over the flood wall at 16:15 and reached 30 cm deep by 17:30. | “100% the fault of the greedy new Glanrafon Retail Park... worst planning disaster” | |
| Witness B: Mark Evans (Retail Park Manager) |
|||
| Witness C: Dr Owen Rhys (Hydrologist) |
None (uses an objective, balanced scientific tone). |
(b) Why might Witness A and Witness B each have a personal motive to exaggerate or blame a single cause?
Look at the 2019 versus 2026 storm comparison table in Section 3 of the stimulus sheet. Both storms dropped exactly 48 mm of rain with peak rainfall at 14:00.
(a) Work out by how many hours (or minutes) the lag time shortened between 2019 and 2026, and by how many cumecs the peak discharge increased.
(b) Explain step by step how replacing 4.5 hectares of permeable grass meadow with impermeable tarmac and storm drains shortened the lag time and pushed peak discharge above 40.0 cumecs. Use the words infiltration, surface runoff, lag time and peak discharge.
Write a balanced report of around 150 words (130 to 170 words) for Pont y Glyn Community Council synthesising the witness statements and river data. Follow the 3-paragraph plan on the board: (1) What the hydrograph shows (48 mm rain, 14:00 peak rain, 17:30 peak discharge of 52.0 cumecs, 3.5-hour lag time), (2) Witness evaluation (why Siân Parry’s timing is right and Mark Evans’s 14:30 / 100 mm claims are wrong), and (3) Physical + human causes (saturated upland peat bog plus the 4.5 ha impermeable car park compared with 2019).