of irregular waves. The gage was developed because runup maxima caused 

 by irregular waves have proven difficult to accurately record by visual 

 observation. The gage provided a complete record of the time history of 

 the location of the air-water interface on the runup board. Sections of 

 runup record and the record of the causitive waves are shown in Figure 2. 

 Incident wave conditions were monitored by a parallel wire-resistance 

 wave gage located 2.5 feet (0.76 meter) seaward of the toe of the 1 on 10 

 slope. The location of the runup board and the position of every 10th 

 runup sensor contact is shown in Figure 3. 



A disadvantage of the runup gage was that it was impossible to tell 

 from the runup record if there was a malfunction in the relays. The gage 

 used 120 mechanical relays and a few relays had to be adjusted every week 

 or so to obtain proper operation. No runup data were collected until all 

 relays were operative. Another problem was the copper runup sensor con- 

 tacts that needed cleaning about every 2 weeks for proper operation. 

 Cleaning the contacts required draining the tank which was inconvenient. 



3. Runup Structure . 



The slope seaward of the fiberglass runup board forming the runup gage 

 was originally a 0.5-inch-thick plywood board which was later replaced with 

 a sheet of 0.25-inch aluminum. The plywood lacked sufficient stiffness and 

 was difficult to keep properly alined due to continual warping. The ply- 

 wood also seemed to encourage the growth of algae. The aluminum sheet 

 corrected these problems; however, aluminum oxide formed on the submerged 

 surface of the sheet and had to be removed from time to time. The loca- 

 tion of the plywood board and aluminum sheet is shown in Figure 3. The 

 supports for the runup slope were made of wood. 



4. Pressure Transducers. 



Pressure transducers were used with the runup gage to determine their 

 usefulness in estimating the limits of runup, the vertical thickness of 

 the runup wedge, and the ..overtopping potential. The transducers were 

 located in a dry chamber of the wave tank behind the runup board and 

 connected to the face of the runup board by flexible plastic hoses. Only 

 four pressure transducers could be used at one time but there were 10 

 locations where they could be used. The four locations of the transducers 

 used in this study were designated 1, 3, 4, and 5. Elevations of hose 

 openings on the runup board, relative to the Stillwater level, were -0.2, 

 0.0, +0.1, and +0.2 foot for locations 1, 3, 4, and 5, respectively. The 

 four pressure transducers were each mounted on a lorry gage so they could 

 easily be raised and lowered to obtain static pressure calibrations. The 

 location of the transducers and hoses is shown in Figure 3. 



The transducers had a full-scale range of either 0.5 or 1.0 pound per 

 square inch. They were very sensitive and could detect a thinner layer of 

 water on the runup board than detected by the runup gage. Normally, a 

 depth of about one- eighth of an inch of water over the runup contact was 

 necessary to activate a relay of the runup gage. There was little trouble 



10 



