A brief description is given of vork being carried out in the Mersey- Estuary, England. This work is part of a sedimentation study of the area, and has necessitated many days' field observations at stations distributed along and across the Estuary. Attention is drawn to the factors influencing the sediment movement and the variables, such as velocity, suspended solids, salinity and temperature that must be measured in order to define the sedimentation complex adequately. A study is made of the effect of variations in temperature and tidal range upon the mean concantration of suspended solids observed at stations in the Estuary; the relationship proposed is of the form