I don't have the hydrological constants for the location of my design - can I use another set of data?
No, data is specific to a location, and there are no default or general values that can be used. Use the maps to get the data for your location from the National Grid reference, interpolating values as necessary.
Can I take data directly from a CAD package?
No, this is not a CAD program as such. You will have to extract the data that is required and enter it into the program. If you are content to let the program calculate gradients, then all you need are the areas drained and the length of each section. Data can be exported as a DXF file.
When I run the surcharge option for my design, there is one section that always shows up as flooded - should I enlarge this section?
Your system has been sized for the return period that you entered - the default is a five year storm. Obviously, increasing the return period will increase the rainfall intensity, and potential problems will become apparent. There is no need to increase the pipe diameter of this section unless you want to utilise the normal spare capacity as storage during the greater storm.
How can I increase the storage capacity of the system?
One easy way is to increase the diameter of the pipes near the outfall, both in the index run and in any branches that come in near this point - use the Preferred diameters option to over-ride the calculated sizes. Another option is to create a blind branch with a minimal gradient of large diameter pipes at the outfall to act as an underground reservoir. Both of these possibilities are only applicable if there is sufficient cover for the larger pipes.
I need to culvert a small stream towards the end of the index run - how do I allow for this?
You will need to obtain the flow rate of the stream, and enter this as extra flow to the section that will carry it into the system. A small weir or backdrop from the incoming pipes to the outgoing section will help prevent backing up and flooding of the incoming index run. The stream may need a small lagoon and a flow regulator to maintain a constant flow during times of raised water level in the stream, and possibly a bypass weir to prevent serious flooding. The section on weir calculations will be useful.
The proportional velocity varies with the hydraulic mean depth, whereas the pipe full velocity is often slower - which value should I take?
Always use the pipefull velocity, as you would in hand calculations using Lloyd-Davies and charts. The proportional velocity is what is actually happening at that moment with those parameters (proportional area and hydraulic mean depth). The problem with using proportional velocity, with its increased flows is that a small wave can occlude the lumen of the pipe, causing the HMD to drop to unity and thus giving a decreased flow rate (hydraulic jump) due to a decreased velocity that is perpetuated while those flow conditions persist.
Can I use the excavations data for QS work?
No, it is safer to use your QS. This option is there so that different designs of the same system can be compared or approximately costed - for example, a shallower gradient will reduce the depth of excavations, but the possibly larger diameter pipes will increase the excavation width.
I need to produce a design for Spain - how can I use a UK based program for this?
You will need to obtain rainfall data for the location of the design. You will need the intensity of rainfall for the first 30 minutes of the storm that you are designing for. Enter the data in the normal way, and when sizing, load in the rainfall intensity profile that you have generated. The format of the file is fixed - see the manual for an example file. Note that this file must be stored as ASCII text, and not from an office word-processor - use Notepad to create the file
