Estimation of runoff peak is needed to assess water availability, in order to support the multifaceted water uses and functions, hence to underscore the modalities for efficient water utilization. The magnitude of storm rainfall acts as a primary input for basin level runoff computation. The rainfall-runoff linkage plays a pivotal role in water resource system management and feasibility level planning for resource distribution. Considering this importance, a case study has been carried out in the Hancheon basin of Jeju Island where distinctive hydrological characteristics are investigated for continuous storm rainfall and high permeable geological features. The study aims to estimate unit hydrograph parameters, peak runoff and peak time of storm rainfalls based on Clark unit hydrograph method. For analyzing observed runoff, five storm rainfall events were selected randomly from recent years’ rainfall and HEC-hydrologic modeling system (HMS) model was used for rainfall-runoff data processing. The simulation results showed that the peak runoff varies from 164 to 548 m3/sec and peak time (onset) varies from 8 to 27 hours. A comprehensive relationship between Clark unit hydrograph parameters (time of concentration and storage coefficient) has also been derived in this study. The optimized values of the two parameters were verified by the analysis of variance (ANOVA) and runoff comparison performance were analyzed by root mean square error (RMSE) and Nash-Sutcliffe efficiency (NSE) estimation. After statistical analysis of the Clark parameters significance level was found in 5% and runoff performances were found as 3.97 RMSE and 0.99 NSE, respectively. The calibration and validation results indicated strong coherence of unit hydrograph model responses to the actual situation of historical storm runoff events.

Abstract
 1. Introduction
 2. Study area and data sources
  2.1. Study area
  2.2. Data sources
 3. Methodology
  3.1. Storm events selection
  3.2. Initial value selection
  3.3. Calibration of Clark parameters
  3.4. Model performance
 4. Results and discussions
  4.1. Data calibration for unit hydrograph parameterestimation
  4.2 Statistical performance analysis for unit
  4.3 Model validation
 5. Conclusions
 REFERENCES

• Kanak Kanti Kar(Department of Civil Engineering, Jeju National University)
• Sung-Kee Yang(Department of Civil Engineering, Jeju National University) Corresponding author
• Jun-Ho Lee(Department of Civil Engineering, Jeju National University)