The WAVES team was tasked with addressing homeowner problems with erosion along their property lines touching the Willamette River. Wave energy produced by boat activity in the river was found responsible and the team picked up this challenge with great enthusiasm.
Unwanted wave energy can be addressed in three main options. The first option is wave attenuation where the goal is dissipate the energy carried by the waves before it reaches the shores or other property such as docks and small boats perched near shore. The second option is energy capture where wave energy is transferred to more useful forms of energy such as electricity or providing power to drive another system. The final option is the homeowner’s next available option which may be installing costly rip rap and other erosion control systems that require lots of unwanted paperwork on the homeowner’s behalf which comes with fees for each document.
The team chose the direction of wave attenuator after considering several criteria and ranking them by importance. The main goal was to reduce erosion in a manner that avoids coming into conflict with environmental regulations. The method of reducing erosion should be mobile as the dock and shoreline of the property is dynamic with both seasonal activity and changing river levels. Its overall cost should be less than the homeowner’s next available option which typically means spending at least $3000 to add rip rap to their property. As such, energy capture was deemed less important for the purpose of this project.
What is a Wave Attenuator?
The team’s method for reducing wave energy was to implement a system of wave attenuators. Wave attenuators reduce the wave energy carried by surface waves through two main methods: (1) a change in momentum of individual particles in the water, and (2) taking advantage of drag forces to dissipate wave energy as heat.
Jute Netting Attenuator Prototype
The team first attenuator design was a jute netting design. The units can be put in series using either a rope or by using carabiners and eyehooks.
Jute netting attenuator with rope. 
Jute netting attenuator with rope in test setting. 
Jute netting attenuator with rope in action.
Cable Attenuator Prototype
The team also tested an attenuator design without jute netting, solely relying on steel cable to hold the logs together. Like the jute netting design, these attenuator units can be put in series using either a rope or by using carabiners and eyehooks.
Tapping wood eyehooks to each log to use with carabiners. 
Cable attenuators connected by eyehooks. 
Cable attenuator with eyehooks and carabiners. 
Cable attenuators connected by rope.
Cost Estimate
The next available option for most homeowners is to apply riprap on their property’s riverbank as a means of erosion control. The problem with this method is that it is very costly, requires the homeowner to apply for several permits, and is almost always installed by a contractor. The WAVES capstone team’s designs are simple enough for homeowners to build themselves, is not expected to require any permits, and can be easily removed and put in place as needed.
Erosion control cost estimates for protecting 15 linear feet of riverbank.
Erosion control cost estimates for protecting 150 linear feet of riverbank.
