圖書典藏及影音數位平台

本署目前共建置156處水位站，其中有83處水位站訂定警戒水位並公告在案，未訂定警戒水位者共計73站。惟莫拉克颱風後，各界對於警戒水位之應用有更高之期望，因此，實有必要對已訂定警戒水位之水位站重新進行警戒水位檢討，並對未訂定警戒水位之水位站評估是否須新增訂定警戒水位。 本署預定於99年度於中央管河川及區域排水增設約48處水位站，亦須配合新訂警戒水位。 另本署於98年度完成第五河川局之中央管區域排水警戒雨量訂定，包括北港溪支流三疊溪之興安排水、朴子溪之嘉義、麻魚寮排水與八掌溪之後庄與湖子內排水，今（99）年度應於汛期間進行颱洪事件之檢驗，經檢討評估後方能實際應用公告實施。

In Taiwan, the hydrologic characteristics have had obvious change in the past decade. The rainfall has a high intensity in a short duration at some areas. For example, the rainfall amounts of many watersheds sometimes were over those of design rainfalls. In addition, the drainage system could not timely drain surplus rainfall then result in inundation disaster in low-land region. Especially, after the Morakot typhoon in 2009, Fanapi typhoon and Magi typhoon in 2010, the application of the warning stages and the warning rainfalls will have more expectation at the inundation areas. This project results can provide the warning stage and warning rainfall information which is important to river safety and evacuation of residents at the inundation area. Therefore, the associated agencies can have more rescued time. The degree of difficulty of the rescue of the disaster at the inundation area will then be reduced. The major goals of the project are to review and establish the warning stages of 168 gauge stations of 25 central authority’s rivers, 4 gauge stations of 4 local authority rivers and 17 gauge stations of 15 central authority’s drainage systems. There are 189 gauges with the warning stages stations to be reviewed and established. Beside, the warning rainfall values have been established for the central authority’s drainage systems of the Fifth River Management Office of Water Resources Agency in 2009. In this year, they are further tested and verified during the typhoon or torrential rain period. In order to let the related staffs understand the establishment procedure of the warning stages, three training courses and four local discussion meetings were held in this year. The goal of the training courses is to train the related staffs having the ability of establishing or revising the warning stages of central authority’s rivers and drainage systems. According to the four local discussion meetings had obtained the same view of the early warning time in central authority’s rivers, included 2 hours of 1st degree warning stage and5 hours of 2nd degree warning stage to reach a river control level（e.g., top bank or design flood water level） and 2 hours of 3rd degree warning stage to reach river floodplain. The need of establishing the 3rd degree warning stage depends the land-used of the floodplain or not. Warning stages of central authority’s drainage systems are divided two degrees. The early warning times are 2 hours of the 1st degree and 3 hours of 2nd degree to reach the control level of the drainage systems. After the initial establishment of warning stages testing and possible revise is required in future. At central authority’s drainage systems of the Fifth River Management Office of Water Resources Agency, we designed and set up some water meter labels in the flood prone areas. In the future if the inundation events occur, neighborhood head or local inhabitant can assist to view the inundation depth and timely record data with time, and send it to related disaster prevention unit. Those inundation depth data can also be useful for overland flow model. On the practice operation of warning rainfall of drainage systems, the Central Weather Bureau released 727 torrential rain and 829 torrential rain, Namtheun typhoon, Lionrock typhoon,, Fanapi typhoon, and Megi typhoon in this year, we monitored the instant water level, rainfall and predicting rainfall and analyzed the warning rainfall. Besides 727 and 829 torrential rains, other typhoons had not reached the threshold of the warning rainfall. According to two torrential rains practice operation and testing, we obtained satisfactory warning predictions according to the warning rainfall establishment. Because the rainfall cases were limited, that the typhoon, torrential rain tests need to be carried out continuously in the future. After the warning rainfall testing finish, the Fifth River Management Office of Water Resources Agency central authority’s drainage warning rainfall values can be bulletined. Water Resources Agency set up 48 new gauge stations and the associated warning stages in this year. It is suggested that the first step is practice operation and testing the warning stages, second step obtain the water level data to review and revise, and finally bulletin the warning stages. On other hand, the central authority’s drainage warning stages and the warning rainfalls should be integrated to reach the inundation and over-bank flow early warning purpose. Finally, it also needs further to study and establish warning stages and the warning rainfalls at the local authority’s drainage systems in future.