Sentence:  He improvised as he went along , completing a life-size clay figure , then bought yards of an inexpensive material from a draper , wet the lightweight cloth in a basin and covered it over with clay that Argiento brought from the <WSD>bank</WSD> of the Tiber , to the consistency of thick mud . 
Meaning of the word marked with <WSD> tags:  sloping land (especially the slope beside a body of water)