2d Modeling versus 1d Modeling: I still like 1d modeling and it works excellent in areas like the Piedmont or hilly regions where the velocity stays up. Those places that have the typical tear drop watershed. But 2d modeling is a very smooth process for those flat watersheds where the water pools or runs in many different directions. And you can have multiple upstream and downstream boundary conditions. It is ideal for coastal plains, where there are distributary canals or ditches, and especially for evaluating the feasibility of wetland restoration projects for the USACE or the NRCS.
No-Rise Certifications: Ultimately, it is up to the local jurisdictions to manage their community floodplains. FEMA is simply the purveyor of the mandated flood insurance rate maps. Local jurisdictions receive guidance on how to keep those rates low and one way is to require the No-Rise Certification for development projects around the floodplain. It usually requires finding the effective HECRAS model or sometimes building one from scratch; having design contours and high resolution LiDAR derived digital elevation models or contours for the immediate surrounding area. Typically flows are kept the same although if there is a site specific hydrology report for stomwater capture and management, flows could potentially be adjusted in proposed conditions. It is according to the goals of the No-Rise Certification. Typical outcomes: 1. There is indeed no impact to the floodplain. 2. There is minor impact to the floodplain/floodway and the analysis will have to be submitted to FEMA for a CLOMR. 3. The impact is not feasible to the client and/or the community and the project is abandoned or re-designed. Examples of common sense projects in the floodway that would most likely not impede it: 1. Soccer fields 2. Bike Trails 3. Any temporary/recreational use that is not obstructive
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