Studies on the Rainfall Characteristics in Chungnam Region(I) Probable Rainfall Intensity in Short Duration in Daejeon Area

충남지방(忠南地方)의 강우특성(降雨特性)에 관(關)한 연구(硏究)(I) 대전지역(大田地域)의 단시간(短時間) 확률강우강도(確率降雨强度)

The characteristic of rainfall intensity in short duration is very important to calculate short-term runoff in small watershed by Rational method. Therefore, the purpose of this study is to derive the most proper formula on the probable rainfall intensity in each return period in Daejeon area. And the results of this study could be utilized for the design of drainage-structures in small watershed, drainage system in urban area and flood control in small river basin. The result s of this study are summerized as follows. 1. Gumbel-Chow method which shows the mean value was chosen to calculate the probable rainfall in tensity in each return periods. 2. According to statistical judgement, probable rainfall intensity formula of Japanese type($I={\frac{a}{t+b}}$, see Table-6) shows the most proper one among other types of formula like Talbot type, Sherman type and Characteristic coefficient method. Probable rainfall in tensity value of Japanese type in Daejeon area shows well coincidence with the one obtained by applying prof. Park's n-coefficient to Monobe formula $I=({\frac{R_{24}}{24}})({\frac{T}{t}})^{0.5486}$. On the other hand, the value by Monobe formula with n-coefficient of 2/3 which is being used as a disign criterison by M. O. C. shows large difference from the fore-mentioned results (see Table-7). Consequently the value by Monobe formula might be judged that it is too much overestimated one as a design criterion. 3. Short-term runoff in small water shed could be calculated more reasonably in Daejeon area through this probable rainfall in tensity formula.

대전지역(大田地域)에 있어서 재현기간별(再現期間別)에 따른 단시간(短時間) (2시간이내(時間以內)) 강우강도특성(降雨强度特性)을 분석고찰(分析考察)하여, 확률(確率) 강우강도(降雨强度)의 최적식(最適式)을 유도(誘導)해 내므로서 소구역(小區域)의 배수공(排水工)과 도시하수도(都市下水道) 및 하천(河川)의 치수(治水) 이수(利水) 공사(工事)를 위한 신빙성(信憑性) 있는 유출량산정(流出量算定)에 기여코저 본연구(本硏究)를 시도(試圖)한바 다음과 같은 결과(結果)를 얻었다. 1. 단시간(短時間)의 확률강우강도계산(確率降雨强度計算)은 재현기간별(再現期間別)로 거의 평균치(平均値)가 되는 Gumbel-Chow법(法)에 의(依)한 계산치(計算値)를 대표치(代表値)로 채택(採擇)하였다. 2. 강우강도식형별(降雨强度式型別)로 적합도(適合度)를 검정(檢定)하였던바 각(各) 재현기간별(再現期間別) 공(共)히 Japanese type(석흑(石黑)의 엄밀법(嚴密法))인 $I={\frac{a}{\sqrt{t}+b}}$(Table-6 참조)가 최적식(最適式)으로 나타났다. 또한 박교수(朴敎授)가 발표(發表)한 $I=({\frac{R_{24}}{24}})({\frac{T}{t}})^{0.5486}$은 신빙성(信憑性)이 매우 높았으나 반대(反對)로 사용(使用)하고 있는 물부(物部)의 강우강도식(降雨强度式)에서 $n={\frac{2}{3}}$를 사용(使用)함은 매우 불합리(不合理)함을 확인(確認)하였다. (표(表)-7 참조) 3. 2항(項)의 확률강우강도식(確率强雨强度式) 정립(定立)으로 대전지역(大田地域)에 있어서 단시간(短時間) 강우강도(降雨强度)로 합리식(合理式)에 의(依)한 보다 신빙성(信憑性)있는 유출량(流出量) 산정(算定)을 기대(期待)할 수 있게 되었다.