Belmonte (2016) Flash floods in Mediterranean ephemeral streams in Valencia Region (Spain)

Identification

• Journal: Journal of Hydrology
• Year: 2016
• Date: 2016-03-19
• Authors: Ana María Camarasa Belmonte
• DOI: 10.1016/j.jhydrol.2016.03.019

Research Groups

• Department of Geography, University of Valencia

Short Summary

This study evaluated rainfall-runoff conversion and flash flood generation in five Mediterranean ephemeral streams in Spain using long-term hydrological data, revealing key rainfall characteristics and basin responses influencing flood events. It identified two distinct types of flash flood events based on seasonality and rainfall patterns.

Objective

• To evaluate the processes of rainfall-runoff conversion and flash flood generation in five Mediterranean ephemeral streams in the Valencia Region, Spain.
• To analyze the influence of rainfall characteristics on basin response, particularly under dry antecedent moisture conditions, using the Carraixet Basin as a case study.
• To assess correlations between main indicators of precipitation and flow.

Study Configuration

• Spatial Scale: Five Mediterranean ephemeral streams in the Valencia Region, Spain, with basin sizes ranging from 25 square kilometers to 450 square kilometers. A detailed analysis was conducted for the Carraixet Basin.
• Temporal Scale: 142 flash flood events registered between 1989 and 2007. Hydrological data were collected every 5 minutes since 1988.

Methodology and Data

• Models used: A simple index called Momentum of Maximum Intensity (MMI) was developed to describe the influence of rainfall intensity on hydrographs. Correlations between precipitation and flow indicators were assessed. Initial abstractions (Ia) were calculated from basin characteristics.
• Data sources: Detailed hydrological information from the SAIH network (Automatic Hydrological Information Systems) of the Jucar River Water Authority.

Main Results

• Flash floods were generally generated by average accumulated rainfall of approximately 100 millimeters at high intensities, which could exceed 300 millimeters per hour.
• Initial abstractions and average water losses during rainfall-runoff conversion were significant, with runoff coefficients of 6% and runoff thresholds of 62 millimeters.
• No correlation was found between initial abstractions (Ia) calculated from basin characteristics and empirically obtained runoff thresholds (P0), raising doubts about the validity of the Ia method for predicting floods in ephemeral streams.
• Accumulated rainfall was highly correlated with flood volume, peak flow, and water balance indicators, while intensity indicators were more related to basin response times and influenced lag time.
• High peak flow was well predicted by accumulated rainfall in combination with high reduced mean intensity and low persistence.
• Two types of events were identified:
  1. Summer and early autumn events: Characterized by fast responses, intense rainfall concentrated at the beginning of the storm, and high values of persistence and irregularity, generating hydrographs resembling the rain pattern.
  2. Winter and spring events: Characterized by less intense rainfall, accumulating more total rain but with lower maximum intensities occurring at the end of the episode, leading to delayed basin responses and hydrographs significantly influenced by the basin characteristics.

Contributions

• Utilized a unique, long-term, high-resolution dataset from the SAIH network for Mediterranean ephemeral streams, where data availability is typically scarce.
• Developed the Momentum of Maximum Intensity (MMI) index to quantify the influence of rainfall intensity on hydrographs.
• Provided an empirical evaluation of rainfall-runoff processes and flash flood generation in Mediterranean ephemeral streams, offering insights into their hydrological behavior.
• Challenged the applicability of the initial abstraction (Ia) method for flood prediction in ephemeral streams based on empirical findings.
• Characterized and differentiated two distinct types of flash flood events based on seasonal patterns and rainfall characteristics, enhancing understanding of flood dynamics in these environments.

Funding

[No funding information was provided in the article text.]

Citation

@article{Belmonte2016Flash,
  author = {Belmonte, Ana María Camarasa},
  title = {Flash floods in Mediterranean ephemeral streams in Valencia Region (Spain)},
  journal = {Journal of Hydrology},
  year = {2016},
  doi = {10.1016/j.jhydrol.2016.03.019},
  url = {https://doi.org/10.1016/j.jhydrol.2016.03.019}
}