The seal increases with the height of flooding and the pressure of the liquid on the ground sheet.
The leakage rate is less than 4 L / min per linear metre of smooth ground (concrete type).
If this leakage rate is deemed too high it is possible to significantly reduce it. To do so, you have to spread a mastic or silicone seal (cartridge type) under the leading edge of the barrier, or any kind of natural product like treacle | viscous material, in order to increase the adhesion of the dam on the soil and fill micro cracks.
The sealing depends on the soil surface state (the smoother the floor, the better sealing) and its draining effect (to be considered for long lasting floods).
Leakage rate generally observed by type of ground, without extra sealing action.
Concrete or new asphalt < damaged concrete < cobblestones < lawn < topsoil < sand < gravel < pebbles < 10 L / min