Hydrocad and infiltration
Hydrocad and infiltration
(OP)
hi
This is great forum. I'm new to Hydrocad and i have a issue with a infiltration. I have a parcel 3.108 ac. in central Wisconsin. Wisconsin code stands that for high imperviousness sufficient runoff volume of the post- development infiltration volume shall be at least 60% of the pre-development infiltrations volume based on 1 and 2 year 24h peak runoff. My problem is for 1 and 2 year event my runoff is 0 i`m not discharging water from the site. i`m not sure how i can find out how much rain is infiltrate at 2 year storm. Any suggestion how to solve this. Thank you all
This is great forum. I'm new to Hydrocad and i have a issue with a infiltration. I have a parcel 3.108 ac. in central Wisconsin. Wisconsin code stands that for high imperviousness sufficient runoff volume of the post- development infiltration volume shall be at least 60% of the pre-development infiltrations volume based on 1 and 2 year 24h peak runoff. My problem is for 1 and 2 year event my runoff is 0 i`m not discharging water from the site. i`m not sure how i can find out how much rain is infiltrate at 2 year storm. Any suggestion how to solve this. Thank you all





RE: Hydrocad and infiltration
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Hydrocad and infiltration
RE: Hydrocad and infiltration
RE: Hydrocad and infiltration
Most obvious error I can think of is you entered acres where the program expected square feet.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Hydrocad and infiltration
Sorry for confusion. I have 0 cfs in pre development and i need to infiltrate 60% of pre in post conditions.
RE: Hydrocad and infiltration
Please complete your statement: "I need to infiltrate 60% of pre..."
60% of what? Please be precise.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Hydrocad and infiltration
I think I understand what you're getting at, but I want to be sure. Let me just get this started and I'm sure Peter or beej will round out the edges.
Is your pre-development such that there is no runoff? 20 acre watershed, low CN, long Tc?? There just isn't any runoff because the design storm is too low for the watershed to produce any runoff, and HydroCAD is telling you this. So how do you infiltrate 60% of zero, because your pre-development site sure is infiltrating a lot of water, so we can't just pave the entire site and say this all works.
This seems to be one of those things you need to work out with your reviewer, and you may need to just do some math with a pencil and paper here.
Lets use that same 20-acre watershed, CN=31, Tc=65 mins, 2-year 24 hour storm = 3.30"/hr
Using the above 239,580 ft^3 is infiltrated across your site, 60% of which is 143,748 ft^3 which would be your infiltration requirement.
RE: Hydrocad and infiltration
Sorry for slow respond.
You are right with everything.
Everything has to be for 2 year event 2.90"/hr. The site is 3.108 ac, grassy field with flow path 330 ft (from SE to NW) CN=39, slope 1.3%, TC= 2.4 min. On the edge of the property there is a ditch (is going a round the property S to E to N). On the West there is a access road.
Can you tell me the formula you used?.
Also i would like to know, how i can enter the infiltrated volume in to the hydrocad to design underground infiltration device.
Thank you for your input
RE: Hydrocad and infiltration
But for you I would do:
(2.9/12 ft/hr)(24 hrs/day) = 5.8 ft/day * (3.108ac)(43560 sf) = 785,230 cf/day * 60/100 = 471,138 cf is your infiltration requirement.
RE: Hydrocad and infiltration
RE: Hydrocad and infiltration
I would expect the total 2-year 24-hour depth to be somewhere in the range of 2-5 inches, depending on the project location.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Hydrocad and infiltration
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.h...
Looking at the NOAA site the value that was provided 2.9" is the 2-yr 24-hr depth. not the intensity.
I suggest you take another look at your hydrology