Factors affecting runoff from a watershed:\r Which of the following catchment characteristics significantly affect the magnitude and timing of runoff response to a given storm?

Question

Accepted Answer

Introduction / Context: Runoff magnitude and hydrograph shape depend not only on rainfall but also on the watershed’s physiographic characteristics. Understanding these controls is essential for peak discharge estimation, hydrograph synthesis, and flood risk assessment. Given Data / Assumptions: The question lists size, shape, and elevation/relief as influencing factors. Other factors (soil, land cover, drainage density) also matter but are not listed here. Concept / Approach: Hydrologic response is affected by concentration time and storage within the basin. Larger areas typically spread runoff generation over longer times; compact shapes (high form factor) yield flashier peaks; higher relief promotes faster overland and channel flow, reducing lag time. Step-by-Step Reasoning: Size influences travel time and attenuation of flow peaks.Shape influences synchronization of tributary flows (compact → higher simultaneous arrival).Elevation/relief influences energy gradient and velocities, affecting lag and peak magnitude. Verification / Alternative check: Empirical design methods (e.g., SCS Curve Number coupled with time-of-concentration formulas) embed these variables; regional flood equations also account for basin area and slope proxies. Why Other Options Are Wrong: Each of a–c is correct but partial; only (d) captures the complete set of listed factors. (e) conflicts with established hydrologic understanding. Common Pitfalls: Assuming rainfall alone dictates runoff without considering watershed controls. Ignoring the combined effect of slope and shape on peak timing. Final Answer: All of the above

Water Resources Engineering Questions