Leca LWA has the ability to delay water runoff by a principle known as water detention. Proper detention provides a steady and manageable flow of water and reduces the risk of flooding. Leca LWA has a highly porous internal structure and an abundance of voids between the grains. This property allows Leca LWA to detain a flow and thereby reduce the peak intensity of runoff from an area. Thus, Leca LWA will diminish the intensity of water from severe storms and moderate loads through slow release of water during and after a serious down pour.
Without a detaining sublayer the value added from a vegetated or permeable surface can be limited, but with Leca LWA, the flood prevention properties of these surfaces can be maximised. Leca LWA can provide a dependable and robust sublayer, and its intrinsic water detention works regardless of ground infiltration.
Overview of Water Management with LECA LWA
Ideal ground conditions allow for infiltration of surface water to the groundwater level. Leca LWA has many air-filled voids and pores that act as temporary storage space for water. After adsorption, water can seep into the ground by infiltration or be discharged to a nearby deposit. By facilitating infiltration, a more manageable quantity of water is achieved through steady volume reduction of the total runoff.
Leca LWA is great for drainage applications. There are ample voids for water to flow between the grains and fillings. Leca LWA can divert water to more suitable locations, for example if used in construction of swales or closed drainage ditches. If the preservation of natural drainage lines of an area is important, i.e. the preferred pathways of water, Leca LWA can be installed as a load bearing backfill material without disrupting existing drainage plans.
The following examples illustrate how Leca LWA can be used in constructions as a subsurface detention medium. A solution can be constructed as an open-ended system by using the inherent detention capability of Leca LWA. Alternatively, a detention solution can be constructed with a restricted outlet for water. Assessments of components should be done independently and a suitable runoff coefficient for the complete solution should be estimated.