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Discover how StormWiseTM helps professionals model underground drainage, storage, and connected surface-subsurface systems for more informed stormwater management.
When a storm moves across a developed landscape, the most visible story is often told at the surface: rainfall accumulating on streets, runoff moving toward inlets, and water collecting in low-lying areas.
But much of the system determining what happens next is out of sight.
Below streets, parking lots, buildings, and other developed areas lies an interconnected network of pipes, culverts, manholes, storage chambers, detention vaults, infiltration systems, and other infrastructure designed to receive, convey, store, and release stormwater. Understanding how that infrastructure performs, and how it interacts with conditions above and around it, is an essential part of effective hydrologic and hydraulic modeling.
StormWiseTM, Streamline Technologies’ advanced H&H modeling software, provides engineers, water resource professionals, and consultants with the tools to represent these underground systems as part of the larger hydrologic and hydraulic (H&H) environment rather than treating them as isolated infrastructure components.
Following Water from the Surface to the Subsurface
Underground H&H modeling begins before water ever enters a pipe.
The hydrologic phase determines how rainfall becomes runoff based on factors such as rainfall characteristics, soils, and impervious surfaces. From there, inlet interception helps characterize how efficiently runoff moves from streets, parking lots, and other surface areas into catch basins and inlets. Once collected, the hydraulic phase evaluates how that water moves through underground pipes, conduits, and storage systems under gravity and pressure-flow conditions.
StormWiseTM supports this process through an optimized one-dimensional link-node methodology that represents underground pipes, culverts, inlets, manholes, and related system components. These 1D networks can also be directly integrated with 2D overland flow and 2D groundwater modeling with StormWiseTM Expert to evaluate interactions across the broader system.
That integration becomes particularly important when a drainage system is influenced by conditions that cannot be understood by examining pipes alone.
Looking Beyond the Pipe Network
An underground system does not operate independently of its surroundings.
High groundwater conditions, downstream tailwater, surface flooding, and available storage can all influence how much water an underground system can receive, how quickly it can convey that water, and where water may ultimately go.
StormWiseTM Expert can solve 1D flow, 2D overland flow, and 2D surficial-aquifer groundwater conditions within an integrated modeling environment. Its groundwater capabilities calculate heads, horizontal flow, seepage, and leakage while facilitating interaction with surface water through intersecting computational meshes.
For modelers, this provides an opportunity to evaluate the system's complete response.
Instead of asking only, "Can this pipe convey the modeled flow?” the analysis can extend to questions such as: What happens if downstream water levels rise? How could surface flooding interact with the underground network? How might groundwater conditions influence the overall system?
Those connections can be particularly valuable when evaluating complex urban drainage environments where surface and subsurface processes occur simultaneously.
Representing Underground Storage with Greater Detail
Underground detention vaults, oversized pipes, storage chambers, gravel beds, and infiltration systems create another modeling challenge: their available storage can change significantly with elevation and surrounding conditions.
StormWiseTM addresses underground storage through stage-volume nodes, specialized 1D control volumes used to represent subsurface storage. During simulation, the software converts stage-volume relationships into effective stage-area values for solving the continuity equation. Modelers can provide refined stage increments to represent changes in underground storage geometry with greater resolution.
Storage is also considered in relation to connected infrastructure. StormWiseTM extends storage calculations from a node to the midpoint of connected links, allowing pipes connected to a storage feature to contribute their respective control volumes to the modeled system.
The result is a representation in which underground chambers, connecting conduits, inflows, outflows, and surrounding hydraulic conditions can be evaluated together.
Understanding Performance Beyond a Single Storm
A drainage facility’s performance is not always determined by a single design event.
What happens when another storm arrives before an underground storage system has completely recovered?
StormWiseTM Expert’s continuous-simulation capabilities allow modelers to evaluate conditions over extended periods while incorporating processes including evapotranspiration and soil-moisture tracking. This makes it possible to examine how systems respond across successive events rather than assuming every simulation begins from the same initial condition.
For underground storage, that broader perspective can help evaluate drawdown and recovery between storms and provide additional insight into how infrastructure may perform when events occur in close succession.
Turning Subsurface Complexity into Better Decisions
Underground infrastructure represents an important component of stormwater management, land development, roadway drainage, flood studies, and broader watershed analysis. StormWiseTM Pro supports one-dimensional H&H modeling across applications ranging from small-scale site drainage to large-scale watershed studies, while StormWiseTM Expert expands that environment with integrated 2D overland flow, groundwater modeling, and continuous simulation.
StormWiseTM also brings more than four decades of development in H&H modeling. StormWiseTM Pro is nationally accepted by FEMA for NFIP purposes, while StormWiseTM Expert has also received FEMA acceptance and approval for use within several jurisdictions.
That combination of modeling capabilities gives professionals a platform for examining not simply individual drainage assets, but how those assets function as parts of interconnected surface, subsurface, and groundwater systems.
Modeling the Complete System
As communities continue to evaluate drainage infrastructure, flood resilience, redevelopment, and future capital investments, understanding what occurs below ground will remain inseparable from understanding what occurs above it.
The opportunity ahead is to model these environments with greater continuity by connecting rainfall and runoff, surface conveyance, underground infrastructure, storage, groundwater, and downstream conditions into a more complete representation of the system.
That is where StormWiseTM is positioned to deliver meaningful value.
By integrating 1D infrastructure, 2D surface-flow, groundwater interaction, underground storage, and continuous simulation into an integrated H&H modeling environment, StormWiseTM enables engineering and water resources professionals to examine complex systems more comprehensively and use those insights to support informed infrastructure planning, design, and flood-risk management.
Because when it comes to stormwater performance, some of the most important answers may be found where they cannot be seen, below the surface.
Contact our team to discover how StormWiseTM can help you model underground drainage, storage, and connected surface-subsurface systems with greater confidence .
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