Colmation and depth filtration within streambeds : Retention of particles in hyporheic interstices

摘要: Colmation refers to the retention processes that can lead clogging of top layer channel sediments and decolmation resuspension deposited fine particles. Internal colmation, interstices directly below armor layer, may form a thin seal disconnects surface water from hyporheic by inhibiting exchange processes. The settling particles under low flow conditions cause external colmation. Colmated are characterized reduced porosity hydraulic conductivity as well consolidated texture. term ‘depth filtration’ transport storage matrix in interstitial layers. Depth filtration is significance for colloidal particulate inorganic organic matter within into alluvial aquifer. role depth assessed content (given mg per liter) retained coarse framework sediment gravel-bed river Switzerland. Sediment samples were taken freeze-coring with liquid nitrogen down 70 cm piezometers 150 depth. Seventy-two percent mobile smaller than 0.1 mm 50% 0.03 mm. fines tended increase depth, although higher accumulations found at intermediate depths influenced exfiltrating ground water. Interstitial detrital >90 μm showed vertical distribution patterns opposing those total These relationships revealed differential import, storage, three types hydrological zones (infiltration, horizontal advection, exfiltration) cross-section stream.