The GATE Grind

GATE 2025 CE (CE2) – Question 26

Hydrology · Reservoir capacity, flood estimation and routing, surface runoff models · 1 mark · Multiple select

In the context of the effect of drainage density on the run-off generation and the hydrograph at the catchment outlet, all other factors remaining the same, pick one or more CORRECT statement(s) from the choices given below.

  1. Lower drainage density results in higher peak in flood hydrograph compared to that when the drainage density is higher.
  2. Lower drainage density results in lower peak in flood hydrograph compared to that when the drainage density is higher.
  3. Lower drainage density results in a flood hydrograph with a longer time base compared to that when the drainage density is higher.
  4. Lower drainage density results in a flood hydrograph with a shorter time base compared to that when the drainage density is higher.

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Show answer and explanation

Correct answer: (B) Lower drainage density results in lower peak in flood hydrograph compared to that when the drainage density is higher.; (C) Lower drainage density results in a flood hydrograph with a longer time base compared to that when the drainage density is higher.

Explanation

A lower drainage density means fewer and longer flow paths, so the water takes longer to reach the outlet and arrives spread over more time. The hydrograph therefore has a lower peak and a longer time base. A higher drainage density gives a quick response with a higher, narrower peak.