PART V: SUMMARY AND CONCLUSIONS 



33. REMR field visits established that problems associated with runup 

 and overtopping occurred on about 20 percent of the Corps' coastal structures. 

 It was found that the problems could be roughly divided into three general 

 problem areas: (a) wave runup and overtopping of breakwaters and jetties gen- 

 erating excessive wave action on the lee side, a problem usually compounded by 

 additional wave transmission through the structure; (b) wave runup and over- 

 topping of seawalls, sea dikes, and bulkheads causing flooding and/or erosion 

 on the backside; and (c) wave runup and overtopping of revetments causing 

 backside subsidence, erosion, and sometimes collapse of the revetment. On 

 reservoirs, wave overtopping of revetments may cause damage to the upstream 

 dam face or erosion of embankments. 



34. A simple mathematical model is used illustrating the problem area 

 related to wave transmission over and through rubble mounds. The model is 

 interesting and useful because it can evaluate the potential effectiveness of 

 various strategies to reduce wave transmission. 



35. A dimensionless freeboard parameter is defined by Equation 1 and 

 used in Equation 2 to provide a simple wave overtopping model for seawalls. 

 The model is used to evaluate and rank the hydraulic performance of a number 

 of seawall/revetment configurations. This model provides a logical and quan- 

 titative measure of the effectiveness of several methods to reduce overtopping 

 of seawalls. These methods include: 



a. Use of a recurved wall in place of a vertical wall of the same 

 height. 



b. Use of riprap revetments fronting the wall. 



£. Use of a cap to increase the crest height of the wall. 



36. Some problems related to wave overtopping of revetments are noted, 

 and potential solutions are suggested. 



37. Based on the field evaluations and problems, further research is 

 needed to develop and/or improve methodologies of predicting and reducing wave 

 runup and overtopping on existing coastal structures. Various approaches and 

 methods will be applied to each problem area, and laboratory tests will be an 

 integral part of each approach. 



37 



