A storm, its hydrograph and flood management
Connect an exact storm record with exposure, land cover and several management choices.
A storm, its hydrograph and flood management
Original fictional unfamiliar-resource pack. Work across the resources; each describes the same teaching scenario. This is not an official examination paper or a real project forecast.
One fictional storm record
Scroll the diagram sideways to see the full resource.
| Hour | Rainfall in preceding hour (mm) | Discharge (m³/s) |
|---|---|---|
| 0 | 0 | 5 |
| 1 | 4 | 5 |
| 2 | 11 | 5 |
| 3 | 6 | 5 |
| 4 | 0 | 7 |
| 5 | 0 | 13 |
| 6 | 0 | 19 |
| 7 | 0 | 13 |
| 8 | 0 | 7 |
| 9 | 0 | 5 |
| 10 | 0 | 5 |
| 11 | 0 | 5 |
| 12 | 0 | 5 |
Resource description
Hour 0: 0 mm rainfall, 5 m³/s discharge; Hour 1: 4 mm rainfall, 5 m³/s discharge; Hour 2: 11 mm rainfall, 5 m³/s discharge; Hour 3: 6 mm rainfall, 5 m³/s discharge; Hour 4: 0 mm rainfall, 7 m³/s discharge; Hour 5: 0 mm rainfall, 13 m³/s discharge; Hour 6: 0 mm rainfall, 19 m³/s discharge; Hour 7: 0 mm rainfall, 13 m³/s discharge; Hour 8: 0 mm rainfall, 7 m³/s discharge; Hour 9: 0 mm rainfall, 5 m³/s discharge; Hour 10: 0 mm rainfall, 5 m³/s discharge; Hour 11: 0 mm rainfall, 5 m³/s discharge; Hour 12: 0 mm rainfall, 5 m³/s discharge
Land cover and homes
| Reach | Impermeable surface (%) | Homes | Homes in mapped flood extent (%) |
|---|---|---|---|
| Upper reach | 20 | 800 | 20 |
| Town reach | 65 | 1800 | 50 |
| Lower reach | 35 | 1200 | 30 |
Resource description
The extent is one scenario footprint. It is not an annual probability map or a map of all future floods.
Management alternatives
| Option | Capital cost (£ million) | Benefit | Limitation |
|---|---|---|---|
| Upstream storage and wetland restoration | 4.2 | May attenuate peak flow and provide habitat | Land agreements and maintenance are required; storage may fill in extreme events |
| Town flood wall | 7.5 | Protects selected assets up to its design conditions | Overtopping and downstream consequences remain possible |
| Property adaptation and warnings | 3.1 | Reduces some damage and improves preparation | Does not stop floods or secure all transport links |
Resource description
Available capital budget: £8 million. Options are alternatives; their benefits cannot simply be added. Operating costs are separate.
Options
Upstream storage and wetland restoration
Capital cost: £4.2 million
May attenuate peak flow and provide habitat
Land agreements and maintenance are required; storage may fill in extreme events
Town flood wall
Capital cost: £7.5 million
Protects selected assets up to its design conditions
Overtopping and downstream consequences remain possible
Property adaptation and warnings
Capital cost: £3.1 million
Reduces some damage and improves preparation
Does not stop floods or secure all transport links
Stakeholder statements
Town resident: Our road and homes need protection.
Downstream resident: Reducing risk in the town must not increase our risk.
Upstream farmer: Storage on my land needs an agreed payment and responsibilities.
Limits of this resource model
- Peak and lag describe one synthetic storm.
- Surface cover alone does not establish discharge or annual flood risk.