AASHTO HDG

Abstract

<strong>INTRODUCTION</strong> <br>The planning and locating of highway facilities are the first steps in a challenging process of providing a safe and efficient transportation system. Hydrologic and hydraulic requirements are among the facets that must be considered during the early phases of the design process. <br>Water and its related resources are important considerations in the planning and locating of highways and their appurtenant facilities. Although historically only major drainage features (e.g., large rivers, environmentally sensitive areas) have been considered during these early stages, the overall drainage solution must be visualized and studied so that substantial design and construction changes are not required later. The possible effects that highway construction may have on existing drainage patterns, river characteristics, potential flood hazards, and the environment in general, and the effects the river and other water features may have on the highway, should be considered at this time. <br>Hydrologic and hydraulic specialists must be actively involved during the initial project phases to ensure that proper consideration is being given to drainage aspects. This involvement should include participation during the highway location selection phase. Early input from these specialists will result in a better design, both hydraulically and economically. <br>It must be emphasized that early studies are not comprehensive, detailed, technical designs. Rather, most are cursory studies to consider obvious drainage-related problems that may be encountered or created and what type of data needs to be collected for evaluation of possible impacts. The degree and extent of preliminary hydraulic studies should be proportionate with the cost and scope of the project and the perceived flood hazards that may be encountered. This chapter presents a comprehensive overview of possible considerations in the planning and locating of a highway.