Analysis of hydrological characteristics of volcanic sedimentary regions : focused on the Jeju island

다국어 초록 (Multilingual Abstract)

Jeju Island, a volcanic sedimentary region, has totally different hydrological characteristics from those of the inland area of mainland Korea. Basalt, a volcanic rock, shows high permeability and thus low surface runoff. This geographical characteristic affects the island’s hydrology changing most channels on Jeju Island to be dry, and runoff to occur only when the rainfall intensity is high. There are several problems in the rainfall-runoff analysis in Jeju Island. Most of the problems are related the rainfall loss by infiltration. This study proposed an appropriate SCS-CN method in Jeju Island considering these characteristics and the applicability of the proposed method was evaluated. The major results of this study can be summarized as follows.
First, in this study, the SCS-CN method was re-established in consideration of the hydrological characteristics of the volcanic sedimentary region. To this end, from 2012 to 2019, major rainfall events in the Hancheon basin of Jeju were selected, and the runoff data of the 2nd Dongsan Bridge located in the downstream part of the Hancheon basin were analyzed. The initial abstraction was determined as the amount of rainfall occurred from the time when the rainfall event occurred to the time when the direct runoff occurred. Potential maximum retention and curve number (CN) were determined by applying the initial abstraction and the effective rainfall and initial abstraction of each rainfall event to the SCS-CN method. Finally, the distribution of each factor such as the potential maximum retention, initial abstract, CN, etc. was reviewed to determine the appropriate CN and initial abstraction scale of the Hancheon basin. The appropriate conditions for the antecedent moisture conditions (AMC) in the Hancheon basin were determined from the sensitivity analysis according to the AMC.
Second, in this study, the re-established SCS-CN method was verified through analysis of effective rainfall. To this end, the independent rainfall event was extracted and analyzed using rainfall data from the Eongtto waterfall basin in Jeju Island from 2011 to 2019. For each independent rainfall event, the effective rainfall was estimated by applying the method proposed in Chapter 4 of this dissertation and the method of the Guideline for Design Flood Estimation. Next, the occurrence characteristics of Eongtto waterfall were analyzed by comparing the cases of Eongtto waterfalls surveyed through news, newspaper articles, and SNS with the previously estimated effective rainfall. Through sensitivity analysis on the hydrological soil group classification method, the initial abstraction ratio, and the AMC, it was confirmed that the AMC had the greatest effect in estimating the effective rainfall.
Finally, in this study, the agricultural water supply in the Udo region was evaluated, using the proposed SCS-CN method. To this end, first, the topographical characteristics and the agricultural activities of Udo were investigated. Then the overall status and scale of reservoir in Udo was identified through existing literature and field survey. Next, the monthly consumptive water use for major field crop in the Udo region was estimated and compared with the monthly precipitation to estimate the agricultural water shortage. Finally, the effect of the storage of the reservoir on the field crop production in the Udo region was evaluated by comparing the irrigation intervals before and after the consideration of the reservoir.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1 Background of Research 2
• 1.2 Objective and Organization of the Dissertation 8
• 1.2.1 Research Objectives 8
• 1.2.2 Organization of the Dissertation 10
• 2. SCS-CN Method 12
• 2.1 Theory of SCS-CN Method 13
• 2.2 Components of the SCS-CN Method 17
• 2.2.1 Initial Abstract 17
• 2.2.2 Maximum Potential Retention 18
• 2.2.3 Antecedent Moisture Condition 18
• 3. Soil Characteristics of Jeju Island 21
• 3.1 Soil of Jeju Island 22
• 3.2 Classification of hydrological soil group in Jeju Island 28
• 4. Determination of the Maximum Potential Retention, Initial Abstract, CN Using Rainfall-Runoff Data 39
• 4.1 Introduction 40
• 4.2 Estimation Method of Maximum Potential Retention, Initial Abstract, CN by Analyzing the Rainfall-Runoff Data 44
• 4.3 Study Basin and Data 46
• 4.3.1 Study Basin 46
• 4.3.2 Data 48
• 4.4 Determination of Maximum Potential Retention, Initial Abstract, CN 52
• 4.4.1 initial abstraction and CN 52
• 4.4.2 Effect of AMC 58
• 4.5 Conclusion 63
• 5. Verification of the SCS-CN Method through Effective Rainfall Analysis 66
• 5.1 Introduction 67
• 5.2 The SCS–CN Method for Volcanic Sedimentary Regions 71
• 5.3 Study Basin and Data 75
• 5.3.1 Study Basin 75
• 5.3.2 Rainfall Data 78
• 5.4 Evaluation of Waterfall Occurrences at Eongtto Falls 83
• 5.4.1 Derivation of the Effective Rainfall 83
• 5.4.2 Occurrences of the Waterfall 86
• 5.4.3 Analysis of the Parameter Sensitivity of the SCS–CN Method on the Estimation of Effective Rainfall 96
• 5.5 Conclusion 99
• 6. Evaluation of Agricultural Water Supply Using the SCS-CN Method 102
• 6.1 Introduction 103
• 6.2 Agricultural Water Supply Evaluation Method 106
• 6.2.1 Agricultural Water Consumption Estimation Method 106
• 6.2.2 Agricultural Water Irrigation Estimation Method 109
• 6.3 Study Basin and Data 114
• 6.3.1 Study Basin 114
• 6.3.2 Data 116
• 6.3.3 Irrigation Facilities 119
• 6.4 Evaluation of Agricultural Water Supply 133
• 6.4.1 Estimation of Agricultural Water Consumption 133
• 6.4.2 Evaluation of Agricultural Water Supply Considering Irrigation Facilities 142
• 6.5 Conclusion 157
• 7. Summary and Discussion 160
• References 165