FEMA Approved xp2D
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XP Software is pleased to announce that xpswmm2D and xpstorm2D (commonly known as xp2D) has been approved by the United States Federal Emergency Management Agency (FEMA) for two-dimensional flood modeling and mapping for the National Flood Insurance Program (NFIP).
This official approval further reinforces the suitability, accuracy and ease-of-use of these software programs for complex flooding analysis and mapping. The xpswmm and xpstorm programs have been FEMA approved for one-dimensional modeling since 2003.
xp2D is a program for simulating depth-averaged, two and one-dimensional free-surface flows such as occurs from floods and tides and has been the subject of extensive testing and validation. It is specifically orientated towards establishing the flow patterns in rivers, floodplains and urban areas where the flow patterns are essentially 2D in nature and would be awkward to represent using a 1D model. xp2D has been dynamically linked (fully integrated) with the xpswmm and xpstorm 1D solution engine.
XP Software has incorporated the above engines into a user-friendly graphical interface leading the user through preprocessing of input data and model simulation. All of xpswmm and xpstorm’s familiar tools for generating tables, graphs and animations are available for reviewing, analyzing and presenting model results. New 2D and 3D visualization and animation tools produce results that are more readily accepted and understood by managers, decision makers and other stakeholders.
“The ability of additional modeling tools and the ease-of-use of the xpswmm2D software provided a feasible modeling alternative for complex hydraulic and flood plain problems.”
Rohin Saleh, P.E.
Supervising Civil engineer
County of Alameda Public Works Agency
Benefits for the National Flood Insurance Program
The specific applications of the xp2D model that best serve the NFIP community relate to accurate zone determination and maping of flood-prone areas characterized by complex hydrologic and hydraulic features, such as:
- Urban floodplain areas with dual drainage systems, combination of enclosed drainage systems, open channels and overland flow paths where the surface and subsurface flows can interactively be simulated in 1D and 2D
- Braided river systems with significant overbank areas
- Levee-protected areas where flooding may be due to overtopping of levees and/or back up of internal drainage systems
- “Flat” areas where flooding may be caused by heavy rainfall excess rather than by drainage/river system capacity restriction, flow path and its recession over time
- Analyzing flows or overbank spills conveyed over flat terrain where the flow paths vary
- Analyzing dam breaks and levee breaches that cannot be accurately depicted using traditional one-dimensional flow assumptions
- Flood Hazard Mapping – xp2D provides a tool to map the extents of surface flooding (depth and velocity) that can be used to develop emergency response procedures and to design engineering solutions to mitigate the impact of the flooding.
“The xpswmm2D model more accurately accounts for the movement of water and storage within a wide, flat area of floodplain. Having the 2D model seamlessly integrated with the already FEMA-approved xpswmm (1D) allowed for an accurate representation of complex flooding in the semi-urbanized study area. Flood hazard maps have been prepared from the results of the xpswmm2D model and are currently the preferred source for flooding information and regulatory action.“
Candis S. Beaudry, AICP
Director
City of Billings Planning & Community Services Department
The reasons that xp2D serve NFIP goals well in the above areas are numerous.
- The system is designed as a comprehensive, integrated modeling solution for hydrology and hydraulics of riverine systems, complex urban scenarios that may include levees, flood walls, unique terrain features, as well as tidal floodplain areas.
- The 1D/2D linkage in xp2D has the flexibility to simulate inlet capture to storm sewer networks as well as link open channels (rivers and streams) directly to 2D.
- 2D engine is robust and descriptive for flooding simulation. The density of computational points in each cell (9 points) and the simulation of cell sides allow flood walls, road crowns, curbs, buildings and other “thin” edge features to be more precisely simulated in 2D.
- Advanced mapping and graphics, capabilities built into the xp2D software allow the user to create maps, profiles, video animations and accompanying data tables quickly and easily. These tools enhance the creation of DFIRMs and the ability to communicate critical flood information to insurers, government agencies and the public.
- xp2D can use either 1D (lumped parameter) hydrology that applied water to specified inlet points in a drainage system or 2D (distributed) hydrology that allows water to be applied directly to the land surface. The hydrologic results are directly connected to the hydraulic system. This func tionality allows a fully integrated hydrologic and hydraulic solution.
“The use of xpswmm2D provided the necessary solution to a complex hydraulic problem of flow in natural channels combined with wide overland flooding in an urban environment.”
Remleh Scherzinger, P.E.
Engineering Manager
City of Petaluma
Department of Water Resources & Conservation
Mapping and Graphics
xp2D provides the user the ability to visualize spatially varying flood depths and velocities as well as flood inundation boundaries. An extension of the flood mapping abilities include flood contouring for estimating Base Flood Elevations (BFE) to be included in Digital Flood Insurance Rate Maps (DFIRM). The integral connection between xp2D and GIS allows users to reproduce the xp2D flood depths and velocities as an aid to communicating risk to land owners, residents, community elected officials and general public. Additionally, xp2D allows the user to create dynamic replays of simulation results. In other words, video replays of the xp2D simulations with dynamic mapping of flood events can be replayed to audiences for visual aid in communicating flood risk.
