Rain Water Management
Storm Water Management
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 downpour.
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.
Due to urban densification, stormwater runoff in larger cities can cause major problems for the existing infrastructure. Runoff water accumulates rapidly when natural areas are replaced by impermeable surfaces, such as asphalt and roofscapes. Additionally, excess runoff results in proliferation of pollutants and pathogens that may pose a public health risk. In order to increase city resilience against stormwater, local authorities usually encourage local water management efforts. Especially cities have initiated official water management strategies and introduced incentives or regulations towards the reduction of overflows of drainage- and sewer systems.
A governing parameter for water efficiency is the capability to manage water by using sustainable and ecological methods with small environmental footprints. A healthy water cycle can be maintained by implementing measures that simulate mechanisms in natural environments such as forests and grasslands, for example water detention, retention and infiltration.
Basic Water Detention Principle with Leca® LWA
The diagram shows the basic water detention principle with Leca LWA. Reduction of runoff intensity with for an area managed with Leca LWA (blue line) is compared with an impermeable, unmanaged area (red line).
The orange line represents the quantity of water run off on the impermeable area with no water management. The water rapidly saturates and the peak intensity discharge is proportional to the peak rain intensity. Illustrated by the blue line, the porous Leca LWA detains the water, decreases the peak flow intensity, and reduces the average runoff intensity by slowly releasing water during an extended time period. The Leca LWA will rapidly regenerate its capacity for water, even when exposed to successive extensive rainfall.
Finely Crushed Leca® LWA Results
The diagram shows laboratory results of runoff behaviour for a finely crushed Leca-fraction. An extreme event of 27 L/m2 for a 15 minutes rain interval, in a 2 % slope, is simulated. The grey area represents the corresponding, incoming rainblock, and the single black line is the runoff intensity of a reference area without detention measures.
The green area shows runoff of water detained by a 200 mm layer of fine, crushed Leca LWA. The detention effect can clearly be seen, and the total amount of delayed runoff is calculated to be 71 % compared with the reference. In addition, the maximum peak intensity of the runoff is reduced by 53 %.
Coarsely Crushed Leca® LWA
The diagram shows laboratory results of runoff behaviour for a coarsely crushed Leca-fraction. An extreme event of 36 L/m2 for a 15 minutes rain interval, in a 2% slope, is simulated. Coarsely crushed Leca LWA has properties similar to finely crushed Leca LWA, but the larger grains support faster drainage in addition to a water detention effect. 41 % of the incoming water is detained, and the peak intensity is reduced by 35 % compared with the reference.
Round Leca® LWA
The diagram shows laboratory results of runoff behaviour for a large, round, uncrushed Leca fraction. An extreme event of 36 L/m2 for a 15 minutes rain interval, in a 2% slope, is simulated. The primary behaviour is drainage, but water detention can be observed. The high permeability will ensure a steady and almost unrestricted flow of water through the medium. This is ideal for systems where high volumes of water must be readily drained or diverted through the subsurface Leca LWA.
Water management calculator tool
This calculator shows the properties of Leca® lightweight aggregate in flood prevention.
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