LABORATORY EFFECTS IN BEACH STUDIES 



Volume I. Procedures Used in 10 

 Movable-Bed Experiments 



by 

 Robert P. Stafford and Charles B. Chesnutt 



I. INTRODUCTION 



This report (a) documents procedures necessary to conduct meaningful 

 coastal engineering movable-bed laboratory experiments and model studies; 



(b) describes common procedures used in the Coastal Engineering Research 

 Center's (CERC) investigation of Laboratory Effects in Beach Studies (LEBS) 

 to conserve space and avoid repetition in reports on LEBS experiments; 



(c) provides a detailed record of LEBS experimental conditions for future 

 analysis involving presently unrecognized parameters (e.g., tank length 

 was not considered a significant parameter and often was not reported 

 before the LEBS experiments); and (d) provides background on the operation 

 of CERC's portable wave generators which have been used in other investi- 

 gations (Savage, 1959, 1962; Fairchild, 1970a, 1970b; Calvin and Stafford, 

 1970). 



A series of 10 experiments was conducted from 1970 to 1972 to define 

 the amount of wave height variability due to wave reflection and variation 

 in the reflection, and to measure the approach to "equilibrium" profiles 

 for the wave and sediment conditions tested. The same sediment was used 

 in all 10 experiments and the water depth and generated wave energy flux 

 were held constant at 2.33 feet (0.71 meter) and S.8 foot-pounds per 

 second per foot (25.8 joules per second per meter), respectively. Of the 

 10 experiments, 5 were performed in a 6-foot-wide (1.8 meters) tank and 5 

 in a 10-foot-wide (3 meters) tank. 



These experiments were conducted in relatively long, narrow wave tanks 

 with the wave approach direction normal to the initial shoreline, and were 

 expected to be two-dimensional. However, three-dimensional effects were 

 observed in the profile development, the reflection envelopes, and the 

 current patterns. These effects will be discussed in later reports. 



Two experiments were conducted in 1970, one in each wave tank, with a 

 wave height of 0.36 foot (0.11 meter), a wave period of 1.90 seconds, and 

 an initial profile slope of 0.10. The initial test length (distance from 

 the wave generator to the initial Stillwater level (SWL) intercept) was 

 100 feet (30.5 meters) in the 6-foot tank, and 61.7 feet (18.8 meters) in 

 the 10-foot tank. After 54 hours in the 6-foot tank and 62 hours in the 

 10-foot tank, the beach had eroded to the back of the tank. From then 

 until the end of the experiments, sand was periodically added to the back- 

 shore to maintain an adequate supply. The two experiments were repeated 

 in 1971 under the same conditions, except that additional sand was added 

 which shortened the initial test length by 7 feet (2.1 meters) in both 



