WAVE RUNUP ON A 1 ON 10 SLOPE 



by 



John Ahrens 



I. INTRODUCTION 



This study was initiated in 1970 to investigate the runup of irregular 

 waves. To make the results of the study useful to engineers who design 

 shore structures, part of the research effort was directed at comparing 

 the runup of irregular waves to the runup of monochromatic waves. A gage 

 for measuring wave runup was also developed and tested. These efforts 

 help relate the results to wave runup design curves presently available, 

 and provide insight into the runup phenomenon. A prime objective of the 

 study is to identify the. characteristics of natural waves which are 

 needed to predict runup or overtopping on a given structure. These 

 results are being used to plan a comprehensive study of runup and over- 

 topping to be conducted at the Coastal Engineering Research Center's 

 (CERC) new facilities at Fort Belvoir, Virginia. All of the runup data 

 were obtained on a plane, smooth 1 on 10 slope. 



II. EXPERIMENTAL SETUP 



1. Wave Tank and Generator . 



The study was conducted in a wave tank, 2 feet deep (0.61 meter), 1.5 

 feet wide (0.46 meter), and 72 feet long (22 meters) with a water depth 

 of 1.25 feet (0.38 meter). A fiberglass board with built-in gage circuitry 

 formed part of a plane, smooth 1 on 10 slope, terminating on the tank floor 

 about 42 feet (12.8 meters) from the mean position of the piston-type wave 

 blade. A schematic cross-sectional view of the wave tank and the runup 

 slope is shown in Figure 1. 



The wavemaker was hydraulically actuated y and controlled by signals 

 from one or more function generators; one function generator made mono- 

 chromatic waves, and combined signals from two or three function generators 

 produced irregular waves. A typical section from a wave record having 

 three monochromatic components is shown in Figure 2. The wave tank and 

 generator are discussed in Coastal Engineering Research Center, 1968. 



2. Runup Gage . 



The runup gage was an adaption of a relay-type, step-resistance wave 

 gage dpscribed by Williams (1969) . Sensor contacts for the gage were 

 copper strips several thousandths of an inch thick, spaced one-tenth of a 

 foot (30.5 millimeters) apart, and bonded to the fiberglass board forming 

 the runup slope face. On the 1 on 10 slope, the gage had a vertical run- 

 up resolution of about 0.01 foot (3 millimeters). It was self-calibrating 

 with a linear response, operated well in freshwater, had a relatively 

 smooth surface, and responded quickly to record the complex runup patterns 



