Drainage studies are needed for the design of highway and railroad structures, for housing developments, and for construction projects. Hydrologic and hydraulic (H&H) analyses determine how water flow is affected by changes to the channel or floodplain.
Bridge & Stream drainage studies typically include a hydrologic analysis to estimate the design peak flow rates, estimated by comparing multiple hydrologic methods. A hydraulic analysis of the project site or the floodplain, with a comparison between the existing and proposed conditions, can determine if the drainage feature is properly sized.
The recent proliferation of LiDAR data across the U.S., combined with advances in two-dimensional (2D) modeling techniques has been a game changer in the water resources industry. Publicly-available LiDAR data provides topographic details of vast areas that previously would have required extensive on-site survey. When used in a 2D model, LiDAR digital elevation models answer questions surrounding split flows, ponding and flood attenuation, and complex flow scenarios. LiDAR data can allow for a cost-efficient desktop study ahead of or in lieu of on-site reconnaissance. Where LiDAR data is unavailable, Bridge & Stream can collect topographic data using imagery collected from UAS or drone systems.
Drainage study results may include floodplain elevations and boundaries, identification of proposed drainage structures, scour protection recommendations, and permitting requirements. Structural recommendations are generally based on constructability, cost, and environmental considerations.