modeling stormwater flow through a stone trench
modeling stormwater flow through a stone trench
(OP)
I was hoping for some guidance on how to model stormwater flow through a stone trench in HydroCAD. What I have is a gravel access road which was constructed across the end of a field without a roadside ditch. The property owner is complaining about flows from the road causing erosion in his field. There isn't enough space within the r/w to construct a full ditch but I was thinking I could construct a stone trench along the road which would discharge to the culverts. I'm just not sure how to model that. Any thoughts?





RE: modeling stormwater flow through a stone trench
The answer depends on the design details and how you expect the system to behave. If it behaves like a level pool, you could use a pond with a void setting for the stone, plus appropriate outlets.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: modeling stormwater flow through a stone trench
What I have done so far is to use PA DEP's E&S Channel Worksheet to determine the cross-sectional area needed carry the flows for the 100-year/24-hour event assuming the trench was empty, then check the cross-sectional area of the trench filled with stone. This is the same method used for riprap channels. I just have no way to show these trenches in the model.
RE: modeling stormwater flow through a stone trench
Another option is to estimate the travel time through each trench section and include it in the travel time for the adjacent subcatchment.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: modeling stormwater flow through a stone trench
RE: modeling stormwater flow through a stone trench
RE: modeling stormwater flow through a stone trench
RE: modeling stormwater flow through a stone trench
psmart, your recommendation for an equivalent cross-section seems to be my best option for modeling.
cvg, I'm not overly concerned with capacity as even my longest stretch of road generates less than 1 cfs and there is no upslope runoff which would reach the trench. There are existing culverts under the road that I am running these trenches to.
As for cost, frankly a pipe and inlet system would double if not triple the cost. Your still importing stone for bedding material and your adding other material. Plus with inlets, you still need to concentrate and convey flows to those inlets which leads back to my original problem. No room.
Siltation may be an issue. Although this is a gas well access road with infrequent use. My concern is more with vegetation working into the stone. I am indicating they should do a biannual inspection and either clean or replace the stone as needed.
RE: modeling stormwater flow through a stone trench