Disaster Management · TEE · read
Runoff, urbanisation and the lecture formula
Floods
TEE core · taught concepts and descriptive answers; extended sums are optional
Runoff is the part of rainfall flowing over or through the catchment toward a drainage point. Paving and roofs often increase runoff and reduce the time available for drainage. M2 p 88 compares barren land with a township to explain that mechanism.
LaTeX: Q=0.27778CIA| Symbol | Meaning and units |
|---|---|
| Q | Estimated peak discharge in m³/s |
| C | Dimensionless runoff coefficient |
| I | Rainfall intensity in mm/h |
| A | Catchment area in km² |
With rainfall and catchment area held fixed, a higher runoff coefficient gives a larger estimated peak discharge. This explains why land cover, drainage capacity and storage matter in urban-flood answers.
The lecture p 88 mixes its conversion factor and area/output labels. The expression above has consistent units. Its worked barren-land/township example, full conversions and extra exercises are available separately.