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Rating curve and factors affecting runoff

Short answer

A rating curve is a stage-discharge relationship (Q=C(G-a)^b) that converts stage records to discharge. Runoff is affected by climatic factors (rainfall intensity, duration, antededent moisture), catchment properties (area, slope, land cover, soil), channel geometry, and human influences (urbanisation, dams).

What is rating curve? What are the factors affecting run off? Explain.

Rating curve

A rating curve is the graph (or equation Q=C(G−a)bQ=C(G-a)^b) that gives the discharge of a river corresponding to the stage at a gauging section. It is used to convert the observed stage record into discharge.

Factors affecting runoff

1. Climatic factors

  • Rainfall intensity, duration and areal distribution; direction of storm movement.
  • Antecedent moisture (soil wetness), temperature, evaporation and snow-melt.

2. Catchment factors

  • Size and shape: large area gives more volume; fan-shaped basins give sharp peaks.
  • Slope and elevation: steep slopes give fast runoff and less infiltration.
  • Land use and vegetation: forest increases interception and infiltration; urban areas and bare soil increase runoff.
  • Soil and geology: permeable soils give less runoff; clay and rock give more.
  • Drainage density and storage (lakes, ponds, depressions) which delay and reduce peaks.

3. Channel factors: cross-section, roughness, slope and bank storage.

4. Human factors: dams, diversions, irrigation, drainage, urbanisation.

✓ Answer checked by Claude Sonnet 5.5

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