Where adequate long-term tide data are not available or when it is necessary to capture the dynamics of a complex shoreline or large-scale project (Level 3), numerical simulation of water levels can provide higher confidence in the selection of a design stillwater level. Numerical models account for site specific details and processes that give rise to complex interactions between water and the surrounding natural and built environments. The use of numerical models reduces the uncertainty associated with the representation of relevant coastal processes needed to design roads, bridges, and any other facilities TxDOT may develop. In general, a numeric modeling effort will need to be applied to appropriately capture the complexity of the study area. Table 15-3 describes the applicability of commonly used numerical models for roadway design.

Table 15-3: Applicability of Storm Tide Numerical Models Based on Level of Analysis

	Level 1 Analysis	Level 2 Analysis	Level 3 Analysis
Design or Modeling Inputs	FEMA flood map elevations, NOAA tide station data, USACE sea level maps, CHAMP outputs	FEMA flood map elevations, NOAA tide station data, USACE sea level maps, CHAMP outputs	2D and 3D hydrodynamic models including coupled wave, storm surge, and morphologic inputs (ADCIRC, Delft3D, MIKE21)

Additional information regarding model specifics (e.g., inputs, outputs) for each example can be found in the FHWA’s

A Primer on Modeling in the Coastal Environment

or through consultation with a TxDOT Precertified Coastal Engineer.