Proposal of Early-Warning Criteria for Highway Debris Flow Using Rainfall Frequency (1): Proposal of Rainfall Criteria

확률 강우량을 이용한 고속도로 토석류 조기경보기준 제안 (1) : 강우기준 제안

Abstract

In this study, we propose rainfall frequency criteria for the development of early-warning system based on the evaluation of the highway debris flow that includes the contents of the rainfall recurrence cycle. The rainfall criterion was recommended based on the results of previous researches and the recommended rainfall criterion was 1 hour, 6 hours, and 3 days. At this time, the study subjects were located in Gangwon area and the probability rainfall of 8 stations in Gangwon area was collected. Also, the probabilistic distribution of the 1 hour, 6 hour, and 3 day rainfall criteria to be used for the early warning for the highway debris flow in Kangwon area was estimated through the probability analysis. In addition, we analyzed the correlation between 3 types of rainfall criteria selected from the rainfall data and the actual destructive damages of debris flow at 12 points in 7 lines of Gangwon highways. At this time, the rainfall criterion on the probability distribution was divided into an average value and a lower limit value. As a result of the review, it was found that the case of using the lower limit value of the rainfall according to the recurrence intervalwell simulates the situation of actual debris flow hazards.

본 연구에서는 강우재현주기의 내용을 포함하고 있는 고속도로 토석류 평가를 기초로 하여 고속도로 조기경보 시스템 개발을 위한 강우기준을 제안하였다. 강우기준은 주의경보와 위험경보로 구분하여 선행연구결과를 기초로 하여 적절한 강우기준이 추천되었으며 추천된 기준은 재현주기에 따른 토석류 평가등급별 1시간, 6시간, 3일 확률 강우량이다. 이때, 연구대상은 강원지역으로 하였으며 강원지역 8개 관측소의 확률 강우량을 수집하였다. 또한, 8개 자료의 확률 분석을 통해 강원지역 고속도로 토석류 조기경보에 이용될 1시간, 6시간, 3일 강우기준에 대한 확률분포를 산정하였다. 또한, 강우기준으로 선택된 3가지 강우정보와 실제 토석류 피해와의 연관성 분석을 실제 토석류가 발생한 강원지역 고속도로 7개 노선, 12개 지점의 피해발생시의 강우자료를 수집하여 검토에 이용하였다. 이때, 확률분포 상의 강우기준을 평균값과 하한값을 구분하여 검토하였다. 검토결과, 재현주기별 강우량의 하한값을 사용하는 경우가 실제 토석류 피해시의 상황을 잘 모사하는 것으로 나타났다.

Fig. 1. Severity Rating according to disaster score and fragile score (Kim, 2009)

Fig. 2. Time continuous rainfall and rainfall (Yune et al., 2010)

Fig. 3. Damage shipments of domestic landslide(http://sansatai.forest.go.kr)

Fig. 4. Landslide prediction criteria of the Forest Service (http://sansatai.forest.go.kr)

Fig. 5. Korea precipitation frequency data server (www.k-id.re.kr)

Fig. 6. Location of main area

Fig. 7. Normal distribution table according to rainfall frequncy

Fig. 8. Monthly rainfall before debris flow occurred

Table 1. Comparison of debris-flow decision table

Table 2. Severity level of risk (Kim, 2009)

Table 3. Landslide early warning criteria the Forest Service

Table 4. Latitude and longitude of main area

Table 5. 1 hour rainfall Status

Table 6. 6 hours rainfall Status

Table 7. 3 days rainfall Status

Table 8. Average and standard deviation of probable rainfall

Table 9. Debris-flow hazard example at highway in Gangwon area

Table 10. Rainfall criterion for early warning of highway debris flow

Table 11. Assessment of rainfall criterion by comparison with rainfall data at debris flow occurrence