Water Management Tools
XP 2D Integrated Flood Model

A Realistic View of How Overland Flow Interacts with Existing Systems.

Floods and storm tides cause extensive damage, stress, loss of life, and dislocate communities. To fully understand and manage these risks requires a reliable hydrodynamic engine that accurately predicts flood inundation patterns. FEMA-approved and UK benchmark tested xp2D meets this challenge effectively and reliably.

xp2D, a 2-dimensional overland flow module for xpswmm and xpstorm, gives you the power to analyse and predict potential flood extents, depth and velocity and accurately models the interaction of surface and underground systems in an integrated 1D/2D modelling environment. The software can also be effectively used to simulate and analyse tidal surges, dam breaks and breaches on sewer networks.

xp2D simulates the complex hydrodynamics of floods and tides by combining the full 1D St. Venant equations and the full 2D free-surface shallow water equations.


xp2D is a TUFLOW-based overland flow module available for both xpswmm and xpstorm. This fully dynamic 2D flow capability, coupled with the 1D capability of xpswmm or xpstorm, allows simulation of flows in and out of urban drainage networks and river systems. It provides an incredibly accurate tool to predict the extent, depth, velocity and duration of flooding to evaluate flood mitigation technologies and management practices. Features supporting structural failures (dams, levees, floodwalls, etc.) allow detailed analysis of emergency response scenarios.

All of xpswmm and xpstorm’s familiar tools for generating tables, graphs, and animations are available for reviewing, analysing and presenting model results. New 2D and 3D animation tools make it easy to present results to managers and decision makers.

xp2D is an integrated 1D/2D model that analyses the whole of a drainage area – hydrology, hydraulics, channel flow, pipe flow, overland flow — and is an excellent choice for accurate flood mapping.

Levee Breach Analysis
xp2D is ideal for the following applications:

  • Analysing trouble spots in an existing 1D network – simulating surface flooding, its flow path and its recession after the storm.
  • Analysing tidal surges, dambreaks and breaches on 1D storm/sewer networks – the impact of surface flooding on an existing 1D network can be simulated far more accurately.
  • Analysis of dual drainage – modelling of a road/subdivision design is enhanced with the ability to interactively simulate the surface flows in 2D and the 1D stormwater/sewer network.
  • Analysis of broad surface drainage – perfect application to design and analyse drainage of car parks, commercial sites, golf courses, etc.
  • Analysing impact of flooding of non-connected 1D models – ideal for analysing the impact of cross surface flooding on adjacent non-connected 1D models such as parallel rivers, drainage canals, irrigation systems, etc.

According to the U.S. National Flood Insurance Program (NFIP), there are specific applications of xp2D that relate to accurate zone determination and mapping of flood-prone areas characterised by more 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 over-topping 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.
  • Analysing flows or overbank spills conveyed over flat terrain where the flow paths vary.
  • Analysing 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.

WHY ADD xp2D TO xpswmm/xpstorm?

Accuracy. When it comes to flooding, accurate simulation and forecasting can save lives and property. A simulation model that can demonstrate how water moves over land and how it interacts with its terrain as well as the existing system is essential in protecting lives, homes, businesses and public dollars.

1D/2D Integration. The combination of the 1D network flow with 2D surface flow uses the best description of the flow for each case — no need to use inadequate approximations. See how flood waters on the surface interact with an existing river or pipe system. Watch as storm sewers surcharge, waters flow down streets or across land surfaces and either pool or re-enter the system.

Structures and Terrain. Model not only the land terrain but its specific attributes. Factors in a model can include different types of land use, buildings, structures, dams, levees, fences and more.

Powerful Analysis. Using the powerful and well-accepted TUFLOW analysis engine coupled with the versatile xpswmm or xpstorm 1D analysis engine, xp2D solves the full 2D shallow-water equations on a finite-difference grid. This means that you will get accurate hydraulics answers, stable model runs, and relatively fast run times — key requirements that must be balanced in a model suited for real-world use.

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