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1.雲林溪原為縣管河川，雲林縣政府87年10月8日87府建水字第8703102988號函公告治理計畫，公告範圍為與虎尾溪匯流口至朱丹灣排水匯入處。 2.民國89年，移撥為中央管河川，本次計畫辦理治理規劃檢討。

Yunlin Creek used to be administered by Yunlin County Government, and was promulgated the River Administered by Gentral Government in 2000 by MOEA. Due to several times of earthquakes and typhoons during recent decades, the riverside and surroundings have changed. To meet the social demand, the the original improvement planning of Yunlin River has to reviewed. Yunlin River basin is located in Yunlin County. It is one of the branch of Huwei River of Beigang River basin. The area of the basin is 48.18 km2. It is a typical plain river which has an average basin slope ranged 1/231~1/779. Landuse in Yunlin River basin is dominated by agriculture. The irrigation areas belong to Yunlin Irrigation Association. In recent years, the construction of industrial parks causes heavily water pollution. Most constructions have been established on both sides. However, There are no utilization of floodplain in River zone beacues of Narrow channel and heavily water pollution. Over the years, the mainly flooding areas include the confluence to National Highway No. 1 Bridge, the channel silted up seriously in midstream, and Sec.22 to 23. The flooded areas are mainly farmland. We adopted rainfall data of Da-pu, Dou-liu(Water Resources Agency), Dou-liu(Yunlin Irrigation Association) Dou-nan, and Gou-ba rainfall gauge stations for rainfall analysis. The hydrological rainfall frequency analysis via Log-Pearson Type III (LPT3) Distribution to analyze the storm of yearly maximum 24 and 48 hours in every recurrence (return period, TR). Then, according to Triangular unit hydrograph Method, Dimensionless unit hydrograph Method with the 24 and 48 hours rainfall type to analyze the peak-flow of yearly maximum 24 and 48 hours in every recurrence (return period, TR). After comprehensive comparison, the peak flow in the confluence of Yunlin River, we selected Dimensionless unit hydrograph Method with the 48 hours rainfall type. The peak flow in 25-years recurrence (return period, TR) is 573 cms at the Yunlin River outlet. After the comparison between the riverbed elevations in 1998 and 2016, it’s shown that most sections are deposition trends for a long time. The reasons include the slope of the bed is gentle, flow velocity is slow, and high outward backwater in the outlet section. They make sediment transport efficiency greatly reduce. According to the hydrological flood routing result, Sec.1 to Sec.3 rightbank, Sec.3 to Sec.6 are insufficient due to high outward backwater of the Huwei River. Sec.20 to 21-1 are insufficient due to lower elevation of cross-sections. Sec.22-1 is insufficient because of narrow channel. Elevation of the other cross-sections are higher than water level in TR=25 yr of Yunlin River. The channel and environment of Yunlin River have been improved based on various units management for a long time. It many has completed improvement works according to the original announcement government plan. Most sections of river also can satisfied the protection standard. According to formerly flooded reasons, development situation, land utilization and analysis, the partial river still needed to built constructions, it contains the cross section 3~6, cross section 19~21-1 cross section 22~23 leftbank, and cross section 24~25. Moreover, cross section 7~14 needed dredge by siltation situation. The engineering plans inciude new flood-control structures are about 4,571 meters (levee are about 1,405 meters, embankment are about 3,166 meters). The area of expropriation is 47,725 square meter. Others are not necessary to increase the structure, but they have to strengthen foundations by scoured situation. Overall improvement works funds are about 457.8 hundred million NT. dollars. All costs are hardly available simultaneously in short term; priority process includes the most urgent improvement measure and safety concern for the resident and community. Thus, there’re 2 phases in the execution plan, shown as follows : (I)1st phase: In order to improve the flooded disaster at population crowded districts. The first phase works include levee Works at cross section 3~6, and The widened channel at cross section 22~23 leftbank. All works of this phase cost is about 249.25 hundred million NT. dollars. (II) 2nd phase: The 2nd phase works include levee Works at cross section 19~21-1 and cross section 24~25. it will promote the protection standard of above two areas. All works of this phase cost is about 208.55 hundred million NT. dollars. The annual benefit of whole plan is 5.9735 million NT. dollars and annual cost is 34.367 million NT. dollars. The ratio of benefit to cost is 0.17 that less then 1. However, it has benefit and the positive influence in many aspects after this project completion, including natural disasters prevention, land utilization, landscape, human outdoors activity, ecology, education, water quality improvement, and so on. It also increase residents’ support to the government and the development . Therefore the whole project is quite value and immediate emergency of the investment.