THE EFFECTS OF GEOMORPHIC AND HYDRAULIC PARAMETERS ON THE SEEPAGE OF PORE WATER FROM INTERTIDAL MARSH SEDIMENTS

A numerical boundary integral element model has been used to study the effect of marsh geomorphology on the seepage of pore water into tidal channels and its subsequent recharge by tidal inundation. In general the results show that, regardless of the geomorphic configuration, the locus of maximum seepage flux occurs at or near the intersection of the creek bank and the tide level. In most cases the volume of seepage discharging through the creek bank exceeds by a factor of two or more that emanating from the channel bottom. The ratio of the two seepage components only approaches unity when the thickness of the aquifer beneath the bottom is similar to the width of the bottom and the ratio of conductivity to specific yield exceeds 0.5. For given hydraulic parameters total seepage volume varies directly with creek bank slope and aquifer thickness whereas these factors are inversely related to the ratio of seepage components. Channel bottom width, on the other hand, has no influence on total seepage volume but greatly increases the component ratio as the width approaches zero. Since most of the seepage discharge is derived from sediments within several meters of the creek bank, variations in seepage discharge driven by variations in marsh geomorphology might play a role in the productivity of creek-side cord grass.