There is varied natural landscape in Taiwan. Erosion and sediment control engineering used to be a major strategy for watershed management and planning but ecological conservation in natural environments and industrial development, as well as the development of a sustainable watershed, have become priorities. This study established the factors that are used for landscape assessment for stream regulation works and their weights using a questionnaire survey of experts with different professional backgrounds in order to determine a method to assess the landscape. The factors, “texture and form”, “color”, and “ecology” were used to assess scenic beauty. The analytic hierarchy process (AHP) and the analytic network process (ANP) were used initially and an expert questionnaire was used to determine the criteria and weights for landscape assessment for watershed stream regulation works. The questionnaire results showed that “integration with natural environment” was the most important factor for the assessment of landscape aesthetics for watershed stream regulation works, followed by “availability of greening and vegetation space”. To preserve scenic beauty after watershed stream regulation works, an expert landscape assessment was undertaken beforehand. This study established a means to integrate the design of engineering structures with the natural landscape. Landscape assessments, strategies for architecture, and landscape design were combined to give an aesthetic solution for soil and water conservation engineering in Taiwan.