Sheet drain for basement wall

[EngMan40]

I am designing geocompisite sheet drain system for a basement wall where there is no space for pipe and stone due to shoring. link below is what I have in mind. The typical value for flow rate is for 100% gradient (vertical flow) and Koerner has example for design calcs. for the bottom portion (hydroduct coil 600) where the horizontal flow will have smaller gradient, I am thinking the flow rate will be magnitudes lower than published value. how do I obtain the horizontal flow rate given the published value for vertical one? I have 1 ft of vertical space to place the 600 to horizontally carry the groundwater inside it to the edge where I have the outlet and connector going to stormwater system. with a 100 ft long stretch of wall, I will have 1% gradient if water is up to top of coil 600 sheet drain.

https://gcpat.com/en/solutions/products/hydroduct-drainage-composite/hydroduct-coil-600