In this study Constable shows the view looking from the forecourt of Flatford Mill across a side stream of the river Stour. This had been diverted under the mill to work the water- wheel. The water churned up by the water-wheel left the mill through an archway below the forecourt, which explains the turbulence seen in the foreground of the sketch.
The house is Willy Lott's House, named after the tenant farmer who lived there for over eighty years. It appears in several of Constable's finished paintings, the most famous of which is The Haywain (now in the National Gallery).