Karmokar (2025) Do morphometry and unit hydrograph consistently reflect the flood generation potential? Insights from the analysis of the Himalayan watersheds

Identification

• Journal: Journal of Hydrology
• Year: 2025
• Date: 2025-11-06
• Authors: Shuvasish Karmokar
• DOI: 10.1016/j.jhydrol.2025.134532

Research Groups

• Department of Geography, Lady Brabourne College, University of Calcutta, Kolkata, West Bengal, India
• Murshidabad (Govt.) Model Madrasah (English Medium), Berhampore, Murshidabad, West Bengal, India

Short Summary

This study investigates the consistency between morphometric parameters and unit hydrographs in assessing the flood generation potential of 30 Himalayan watersheds. It finds that a plot of Melton’s ruggedness number (MRn) versus log first order stream magnitude (F1m) provides 100% accuracy in categorizing watersheds by relative peak magnitude, showing 85% agreement with the CWC Synthetic Unit Hydrograph (SUH) model.

Objective

• To investigate the consistency between static morphometric parameters and unit hydrographs in assessing the flood generation potential and susceptibility of watersheds.

Study Configuration

• Spatial Scale: 30 Himalayan watersheds.
• Temporal Scale: Focus on inherent watershed characteristics related to flood potential and susceptibility, not a specific temporal event analysis.

Methodology and Data

• Models used: CWC Synthetic Unit Hydrograph (SUH), Geomorphic Instantaneous Unit Hydrograph (GIUH), multivariate morphometric approaches, bivariate morphometric approaches (specifically MRn vs log F1m).
• Data sources: Derived from watershed morphometry (e.g., stream networks, elevation data for parameters like Melton’s ruggedness number and first order stream magnitude).

Main Results

• The Melton’s ruggedness number (MRn) vs log first order stream magnitude (F1m) plot demonstrated 100% accuracy in categorizing watersheds by relative peak magnitude.
• This morphometric approach showed an 85% agreement with the regionally devised CWC SUH model for flood susceptibility assessment.
• The GIUH model exhibited only 70% accuracy, indicating less consistent and reliable performance compared to the MRn vs log F1m plot and CWC SUH.
• The MRn vs log F1m plot is a practical alternative for classifying watersheds based on relative flood magnitude and flashiness, especially where regional hydrograph models are absent.
• However, morphometric plots cannot estimate quantitative flood parameters like peak discharge (Qp) and time to peak (tp).
• A combined approach is recommended, utilizing bivariate morphometric relationships (e.g., MRn vs log F1m) for relative flood risk assessment and regional synthetic hydrograph models (e.g., CWC SUH) for quantitative flood metrics.

Contributions

• Clarifies the relationship between hydrological behavior, morphometric parameters, and unit hydrograph components, enhancing scientific understanding.
• Provides a practical alternative (MRn vs log F1m plot) for relative flood susceptibility classification in data-scarce mountainous regions.
• Recommends a combined approach for flood risk assessment and quantitative flood metric estimation, improving flood management strategies.
• Supports the development of more accurate flood susceptibility models and improved flood prediction capabilities for researchers and policymakers.

Funding

Not specified in the provided text.

Citation

@article{Karmokar2025Do,
  author = {Karmokar, Shuvasish},
  title = {Do morphometry and unit hydrograph consistently reflect the flood generation potential? Insights from the analysis of the Himalayan watersheds},
  journal = {Journal of Hydrology},
  year = {2025},
  doi = {10.1016/j.jhydrol.2025.134532},
  url = {https://doi.org/10.1016/j.jhydrol.2025.134532}
}