Modeling Energy Loss with Reef Balls


Home -- Project Objectives and Motivations -- What are Reef Balls? -- Background -- Approach -- Results -- References	Project Objectives To evaluate the effectiveness in decreasing wave transmission through physical modeling simulations To evaluate wave energy loss resulting from implementing Reef Balls To expand the conceptual understanding of how reef balls work and apply it to a real world case study Project Motivations Coastal erosion has become an increasing risk for growing populations along the United States' coastline. In 60 years approximately one in four homes within 500 feet of the coast can fall victim to the effects of coastal erosion (FEMA, 2000). Rates of erosion vary throughout the country with one to six feet of erosion per year near the Gulf of Mexico to roughly a foot per year on the west cost. Many current efforts are used to prevent shoreline erosion; however, these techniques are not adequate. A popular method to control shoreline erosion is emergent breakwater. These breakwaters act as a wall to prevent shoreline erosion by decreasing wave energy. Although the breakwaters prevent erosion at an intended location, further down the coast they cause erosion. This occurs because the emergent breakwater forces the wave to bounce back, causing the down-coast waves to become more powerful. This wave force amplification ultimately leads to erosion. Other shoreline erosion management programs are costly to coastal cities. For instance, some cities replenish their beaches through a process called beach nourishment, which occurs about every five years. This process involves importing sand to replace sand lost to erosion. Repeating this process can be burdensome and expensive for governments. On average, a normal beach nourishment project costs about 2 million dollars. Many of these methods present ‘band-aid’ solutions without actually solving anything. Artificial reefs introduce an alternative solution to reduce shoreline erosion without the insufficiencies of current efforts. Artificial reefs act as submerged breakwaters, causing energy from the waves to dissipate as they travel inshore. When waves have less energy, sand drops out of suspension causing either shoreline stabilization or accretion, which is simply sand building up along the shore. Since artificial reefs allow the waves to pass through instead of blocking them, down-coast erosion will not result. The 2001 California Regional and Sand Retention Strategy argued that artificial reefs can be more cost effective than continual spending on beach nourishment (Innes, 2005). It may not seem obvious that the cost is cheaper due to the relatively expensive upfront costs. Initially, construction and materials are expensive, often exceeding what it would take to perform beach nourishment. However, over time beach nourishment costs will exceed the upfront cost of artificial reefs. For instance, the construction of Reef Balls^TM, a type of artificial reef, is initially expensive, but the design has proven to be stable and durable, requiring minimal maintenance. Thus, in the long run, the design is cost beneficial compared to options like beach nourishment.

To evaluate the effectiveness in decreasing wave transmission through physical modeling simulations
To evaluate wave energy loss resulting from implementing Reef Balls
To expand the conceptual understanding of how reef balls work and apply it to a real world case study

Project Motivations

Coastal erosion has become an increasing risk for growing populations along the United States' coastline. In 60 years approximately one in four homes within 500 feet of the coast can fall victim to the effects of coastal erosion (FEMA, 2000). Rates of erosion vary throughout the country with one to six feet of erosion per year near the Gulf of Mexico to roughly a foot per year on the west cost.

Many current efforts are used to prevent shoreline erosion; however, these techniques are not adequate. A popular method to control shoreline erosion is emergent breakwater. These breakwaters act as a wall to prevent shoreline erosion by decreasing wave energy. Although the breakwaters prevent erosion at an intended location, further down the coast they cause erosion. This occurs because the emergent breakwater forces the wave to bounce back, causing the down-coast waves to become more powerful. This wave force amplification ultimately leads to erosion. Other shoreline erosion management programs are costly to coastal cities. For instance, some cities replenish their beaches through a process called beach nourishment, which occurs about every five years. This process involves importing sand to replace sand lost to erosion. Repeating this process can be burdensome and expensive for governments. On average, a normal beach nourishment project costs about 2 million dollars. Many of these methods present ‘band-aid’ solutions without actually solving anything.

Artificial reefs introduce an alternative solution to reduce shoreline erosion without the insufficiencies of current efforts. Artificial reefs act as submerged breakwaters, causing energy from the waves to dissipate as they travel inshore. When waves have less energy, sand drops out of suspension causing either shoreline stabilization or accretion, which is simply sand building up along the shore. Since artificial reefs allow the waves to pass through instead of blocking them, down-coast erosion will not result. The 2001 California Regional and Sand Retention Strategy argued that artificial reefs can be more cost effective than continual spending on beach nourishment (Innes, 2005). It may not seem obvious that the cost is cheaper due to the relatively expensive upfront costs. Initially, construction and materials are expensive, often exceeding what it would take to perform beach nourishment. However, over time beach nourishment costs will exceed the upfront cost of artificial reefs. For instance, the construction of Reef Balls^TM, a type of artificial reef, is initially expensive, but the design has proven to be stable and durable, requiring minimal maintenance. Thus, in the long run, the design is cost beneficial compared to options like beach nourishment.