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HydroCAD Stormwater Modeling - Since 1986

What Are Nodes?
Node Capacity Subcat FAQ Reach FAQ Pond FAQ Link FAQ Pipe FAQ

What are nodes?

Each HydroCAD model consists of a set of nodes that are combined to simulate the behavior of the entire system.  Each node represents a hydrograph operation, such as generating runoff from a subcatchment or routing the hydrograph through a reach or pond.  The individual nodes are interconnected by the routing diagram (shown at right), which specifies how the hydrographs are routed from one node to another.  Please use the links at the top of this page for details on each type of node.

Priced to suit any budget

HydroCAD is available in various node capacities to match your individual needs. For most applications, we recommend the 20-node HydroCAD system for just $825. This is our most popular system and will handle the majority of projects, such as the 9-node watershed shown above.  We also offer smaller systems starting at just $275.  See the order page for full pricing.

How many nodes do I need?

Use this worksheet to estimate the number of nodes in one of your typical projects:

Subcatchment symbol_____ Number of separate subcatchments. Each subcat may contain an unlimited number of flow segments (used to calculate the time-of-concentration), plus an unlimited number of sub-areas and curve numbers.

Pond symbol_____ Number of separate ponds you wish to model. Each pond may include an unlimited number of outlet devices, such as weirs, culverts, standpipes, etc. In addition to detention areas, be sure to consider catch basins or roadway impoundments that create a headwater on a culvert or other "outlet device."  Each of these is modeled as a pond.

Reach symbol_____ Number of reaches you wish to model separately. Do not include open channels that will be handled as a flow segment within a subcatchment, or pipes that will be modeled as a culvert outlet on a pond. Many projects will have no separate reaches.

Link symbol_____ Number of links, used to manually enter a hydrograph, or import a hydrograph from another routing diagram. Most projects will have no links.

_____ Number of text/image nodes, used to enhance the routing diagram with additional text or images.


Your best choice is a program that meets or exceeds this number. (See the order page for details.) If your budget is tight, you can use a smaller program by breaking your project into two (or more) pieces and tying them together with a link. You can always upgrade to a larger program for the difference in cost. Many customers start with a smaller program for their first project, and then enlarge it for a later job. This provides the immediate benefits of HydroCAD while spreading the cost over several projects.

If you need additional assistance in determining the necessary number of nodes, our how-to page can provide some general guidance about setting up your project.

Important: For project review, HydroCAD can open and calculate a project of any size, even if it exceeds your node capacity.  You only need to purchase enough nodes for your actual design work.  For example, a reviewing agency might purchase a 10-node program in order to do some occasional design work, but would be able to open and review projects with up to 1000 nodes.

For further details please read about node capacity.


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