French first stage Vertical Flow Constructed Wetlands (VFCWs) differ from other wetland typologies on granular materials (gravel instead of sand). At the beginning of its operation, raw wastewater flows readily through coarse filter media. However, as time goes by, suspended solids (SS) settle and bacterial biofilm grows within interstitial pore spaces. On the surface, a sludge deposit layer builds up and its structure evolves according to operating (feeding/resting alteration; batch volume) and climate (season; rainfall) conditions (Molle 2014). Finally plants, micro- and macro-fauna participate to the structuration of both sludge deposit and porous media. All these phenomena significantly modify VFCW functioning as they age. Aging participates in improving VFCWs performance but may also be responsible of certain VFCW malfunctions. Furthermore, the accumulation of organic matter and its degradation products inevitably lead to clogging, which may make necessary removals of the sludge layer and clogged porous media. Therefore, understanding how aging acts on VFCWs may help improving their operation and our perception of their life cycle. An ongoing project was conducted/initiated to better quantify and understand how aging acts on porous media of French VFCWs through different combinable complementary approaches: (i) mass-balance analyses based on a recently developed database on French VFCW (Morvannou et al., 2015), (ii) direct observations of porous structures using thin sections and (iii) numerical modelling using a mechanistic model combining multispecies transport, biokinetic degradation and bioclogging (Samsó et al., 2016).