Rill erosion, slumping, and fissuring develop on seepage faces of many sandbars along the Colorado River in the Grand Canyon at low river stage. Three sandbars were instrumented with sensors for continual monitoring of stage, pore pressure, ground-water temperature, and tilt to determine the relation between ground-water flow and sandbar deformation. Data were collected from October 1990 to July 1993 at sandbar -6.5R, which had 17 pore- pressure sensors, 1 stage sensor, 19 temperature sensors, and 8 tilt sensors. Data were collected from April 1991 to March 1993 at sandbar 172.3L, which had 15 pore-pressure sensors, 1 stage sensor, 29 temperature sensors, and 10 tilt sensors. Atten- uation of water-level fluctuation from the zone of fluctuating river stage to the back of the sandbars ranged from 70 percent at sandbar -6.5R to 40 percent for sandbars 43.1L and 172.3L. Shallow tilt occurred at sandbar 43.1L from July 7 to August 10, 1991. Tilt occurred at sandbar 172.3L on May 7-8, June 18-19, and September 1-2, 1991; July 3 and 31, 1992; January 12, 14, 20-21, and 31, 1993; and February 21 and 24, 1993.