During the past few decades in Fengshan creek basin of northern Taiwan, land excessive reclamations were conducted and more and more golf courses have been built on the hillside. As rainy and typhoon season comes, heavy rainfall induced flash floods and surface inundations usually brings significant damages to local populations and destroyed their properties. In order to study the impacts as environment changes, the Fengshan Creek basin is selected as our study site. This study, aimed to understand the effects of climate and land cover changes by modeling future scenarios. We used weather generation model (WGEN) and general circulation models (GCMs) to study scenarios of climate change, and the conservation and land use and its effects model (CLUE-s) was applied to model land cover changes. We then applied the software of HEC-HMS to calculate surface runoff on mountainous area, and implemented WASH123D numerical model for entire watershed simulations. Modeling results were linked to hydraulic routing to discuss the scenarios on the periods of (1) near future (2020-2039 years), (2) future (2050-2069 years), and (3) far future (2080-2099 years). Simulations results indicated that the influence of climate change reveals much apparently effects as comparing to land cover changes. And the future climate tends to getting dryer during dry season, and more wetted of raining season in this area. The ground water levels tended to drop down as land cover changes in the future.