Hydrological Calculations

Hydrology is the study of water movement, distribution, and quality. The hydrologic cycle includes precipitation, evaporation, infiltration, and runoff. The rational method (Q = C × i × A) estimates peak runoff from rainfall. The SCS Curve Number method estimates runoff volume. Frequency analysis (e.g., 100-year flood) uses probability distributions. Rainfall intensity-duration-frequency (IDF) curves relate rainfall intensity to duration and return period.

Governing FormulaQ = C × i × A (Rational method), CN (Curve Number), P_100 = (T/TR) × P

Knowledge Check

10 Questions

1.A catchment has an area of 2 km², runoff coefficient C = 0.6, and rainfall intensity i = 50 mm/hr. What is the peak runoff using the rational method?

2.In hydrology, what is a 100-year flood?

3.The SCS Curve Number (CN) is used to estimate:

4.A catchment with CN = 70 receives 80 mm of rainfall. What is the approximate runoff depth (S = 25400/CN - 254)?

5.Rainfall intensity-duration-frequency (IDF) curves show the relationship between:

6.What is the primary factor affecting the runoff coefficient (C) in the rational method?

7.A catchment area of 10 km² has a mean annual rainfall of 1200 mm and runoff coefficient of 0.4. What is the mean annual runoff volume?

8.The return period (T) of a flood is related to its probability of exceedance (P) by:

9.What is the standard duration used for the rational method in urban hydrology?

10.The Gumbel distribution is commonly used in hydrology for: