Hydraulic Modeling in 2-D: Major Advances in Software Allow Engineers to Model Overland Flow Using 2-D Techniques
How Does It Work?
Generally, a 1-D hydraulic engine is used to model flow through storm sewers or channels, and the 2-D hydraulic engine is used to model the overland flow that occurs when the drainage system capacity is exceeded. However, the results from a 2-D model are only as good as the data used to build the surface model. So, the first requirement for 2-D modeling is an accurate surface model that represents the ground surface. If possible, the surface model should be built with breaklines that represent physical features such as curbs, walls, or changes in ground slope. From this point, the methods diverge depending on the software package.
There are two main approaches for 2-D modeling: triangle-based and grid-based. The advantage of triangle-based is that triangles can be different sizes and provide more detail only where detail is needed. Either way, the software’s mathematical engine solves complex differential equations as the water flows across one element to the next.
2-D modeling can be computationally intensive. It is recommended that engineers only use 2-D modeling where necessary. The best application for 2-D modeling is when flood waters are spreading out over a broad, flat area and moving in more than one direction. Conversely, if the excess runoff is completely contained within a constant cross-section (e.g. street geometry) and moving in only one direction, the engineer would not benefit from 2-D. Depending on the situation, the most appropriate hydraulic model for overland flow may be 1-D, 2-D or a combination of both.