台北市山坡地之开发特性与其对下游水文环境冲击之研究

Study on the Impact of Hillslope Land Development in Taipei City on Hydro-environment in the Lower Reaches

本研究系针对台北都会区四周之山坡地，进行连续之地文与水理分析，目的在了解都市化山坡地之迳流特性，期就定量之研究分析，推估不同型态之土地利用及开发度，对下游水文环境所造成之冲击，并提出对应之建议。本研究首先建立台北市山坡地开发程度与其地文条件之评估模式，再配合於山沟谷口间设置水文环境监测站，以掌握山坡地之动态水文资料。经评估结果，本研究共规划设置六座水文环境监测站，对都市化山坡地之尖峰流量、稽延时间、泥砂产量、地下水位及水质变化进行长期监测。其监测资料，经验证分析之结果显示，当集水区不透水面积提高至４０％时，其洪峰流量将提高２．７倍；同时亦发现当集水区不透水面积在５％以下时，其洪峰流量增加并不显著，但不透水面积提高至２０％～４０％范围之间时，其洪峰流量则有显著提升之现象。故於高度都市化集水区进行水理分析时，应特别考虑都市化现象对迳流机制之影响，同时该集水区之总开发度亦不宜超过３０％，以避免对下游之水文环境造成冲击。

The objective of this research is to study the impact on rainfall-runoff characteristics of slopeland urbanization in Taipei by the investigation of the hydro-environmental change for slopeland development and different types of landuse sites. The hydrologic characteristics studied include the evaluation of the relationships between percentage of development and allowable landuse capability. And, the results achieved are then applied to the planning of field monitoring system for the hydro-environmental study in the future.As the results, six observation stations were established in Taipei. The observation items include the rainfall intensity, sedimentation, water quality and hydrograph. on the time scale.The preliminary analysis of field records compared with unit hydrograph shows that, the impervious area of watershed has been increased 40%, the peak discharge will increase 269%.And for low percentage of impervious area (0￣5% ), the increase of it will cause the peak discharge to increase mildly. But for high percentage of impervious area (20%￣40%), the increase of it will cause the peak discharge to increase dramatically. As a whole, the critical point of the degree of impervious area for the slopeland is around 30%. Above it, the impact of urbanization will accelerate.