圖書典藏及影音數位平台

配合主流河川環境管理規劃及計畫納入支流及水庫上游河川區域已達全流域環境管理計畫目標(126.43公里)

This document is preliminary planning with the aim to prepare the River Environmental Management Plan (REM Plan) for the seven tributaries of the Zengwen River—Guantian, Tsailiao, Houku, Houdan, Youche, Wanchiu and Michi. The main task is to propose the ideal image, management policy and an enhancement plan for each tributary. Information related to water quality, flow quantity, river morphology, ecological health and neighboring landuse has been collected and analyzed to understand the issues that needs to be addressed. Guantian is burdened with poor water quality and ecological health due to the lack of flow from the Wushantou reservoir. It is further restriced by channelization and private farming next to the channel. The planning proposes to release environmental flow from the reservoir and remove the concrete lining. The farming is to be allowed under the regulation of Green Preservation Certificate and the stream reconnected with the neighbouring farm ponds to restore the acquatic habitat. Two bridges are to be preservied as cultural heritage to revitalize a recreational trail along the river. The Tsailiao watershed is characterized by the mudstone and heavy fine sedimentation after storms. The geological context troubles the neighborhood with repeated flooding but also brings about rich fossil that get flushed to the stream bed. An endangered owl and a rare damselfly have been found in the riparian areas. The planning proposes to rebuild 8 bridges that form the bottle neck during the floods. It proposes an in-channel dredging and construction regulation that necessitates reports and halting the work when rare fossil is discovered. The mudstone banks are to be left undisturbed for natural revegetation. Exotic species from upstream reservoir is to be removed to restore the instream biota. The biodiversity of Houku is declining due to the lack of small floods and coarse sediment from the Nanhua reservoir. The longitudinal corridor is blocked by multiple groundsills and crossings. The planning emphasizes sophisticated flow and sediment management that simulates natural flood hydrographs and returns coarse gravel to the stream. Crossings are to be removed or changed to ensure longitudinal pathway. Exotic species that dominate the Nanhua reservoir needs to be removed and monitored continually. Houdan is largely restricted by hard revetment and the bed is scattered with broken concrete pieces. The watershed is underlaid by loose rock materials and lateral channel movement is active. The upper watershed has several resort hotels that draw hotspring from the creek and recent instream construction has not taken acquatic habitat into consideration. The planning stresses regulation on hotspring development and restoration of creek morphology by minimizing protection works and adopting environmental friendly methods in construction. Reforestation and camping ground development is proposed at the Zengwen confluence. Youche, Wanchiu and Michi are tributatry creeks with relatively undeveloped watersheds. The channels have been however largely engineered to prevent lateral movement. Exotic fish and plant species have invaded and resulted in poor bio-diversity. The planning strategies include renaturalizing stream morphology and removing concrete revetment and groundsills, invasive plant cleanning and exotic fish barriers near the confluences. A scenery spot is to be revitalized with access repair. All other development activities will be prohibited in these streams.