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View Full Version : Understanding base flow and its implications on flooded/lost volumes



Abbie
March 11, 2014, 08:13 AM
Hi all,

I'm fairly new to InfoWorks and am trying to assess the impact of various surface water management solutions on flooding using InfoWorks CS. A couple of the options I am considering include constructing overland channels which are quite wide (in an attempt to model water flowing over a road surface). Since base flow is limited to 20mm depth, and the channel is particularly wide and long, the volume of water appears to be significant. This option also appears to fix my flooding problem (with a channel depth of only 21mm).

From my understanding the base flow is a depth applied to each link. Just wondering whether this has any impact on the amount of water going into/out of a node? And whether the baseflow applied is assumed to be "real" i.e. does the model allow the channel to fill from the bottom of the link or does it begin filling from a depth of 20mm? (this seems improbable but clarification would be useful).

Help would be much appreciated.
Thanks in advance,
Abbie

Duncan Kitts
March 19, 2014, 02:14 AM
Hi Abbie,

This is from the help:-

"The simulation engine adds base flow to maintain numerical stability at low depths. It does this by altering the true upstream (higher) boundary condition so that there is effectively a wall of the base flow depth at the upstream end of the conduit. The simulation engine then adds the normal flow for the base flow depth to the flows in the conduit.

At the true downstream end of the conduit, the boundary condition uses the true flow, so that in effect the base flow is lost between the conduit end and
the connected node. This means that node volume balance calculations are based on the true flows."

This means that there is no net generation of flow.