From the introduction:
As you reach the southern end of Lake Quag and cross over the spillway, you find yourself back on the river and paddling south in your canoes. From here on out, the journey to Greyhawk is by way of the mighty Velverdyva River. As you meander through the grasslands heading for the location where the river divides the Yatil Mountains and the Clatspur Range, you find it teeming with all manner of life, both plant and animal, many of which are deadly dangerous. The greatest peril, however, lies in the raging waters through the canyon and the deadly encounter about to take place in caverns deep, lost and buried long, long ago. Will the adventuring party survive the perilous adventures in the Clatspur Range? Find out in Chapter 5 of the Great Flanaess River Adventure!