concrete cubes, which have been used up to ~195 tonnes for the tip of the breakwater at Punta Langosteira near La Coruña, Spain. Preliminary design of armour unit size is often undertaken using the Hudson Equation, Van der Meer and more recently Van Gent et al.; these methods are all described in CIRIA 683 "The Rock Manual" and the United States Army Corps of Engineers Coastal engineering manual (available for free online) and elsewhere. For detailed design the use of scaled physical hydraulic models remains the most reliable method for predicting real-life behavior of these complex structures. Unintended consequences Breakwaters are subject to damage and overtopping in severe storms. Some may also have the effect of creating unique types of waves that attract surfers, such as The Wedge at the Newport breakwater. Sediment effects The dissipation of energy and relative calm water created in the lee of the breakwaters often encourage accretion of sediment (as per the design of the breakwater scheme). However, this can lead to excessive salient build up, resulting in tombolo formation, which reduces longshore drift shoreward of the breakwaters. This trapping of sediment can cause adverse effects down-drift of the breakwaters, leading to beach sediment starvation and increased coastal erosion. This may then lead to further engineering protection being needed down-drift of the breakwater development. Sediment accumulation in the areas surrounding breakwaters can cause flat areas with reduced depths, which changes the topographic landscape of the seabed. Salient formations as a result of breakwaters are a function of the distance the breakwaters are built from the coast, the direction at which the wave hits the breakwater, and the angle at which the breakwater is built (relative to the coast). Of these three, the angle at which the breakwater is built is most important in the engineered formation of salients. The angle at which the breakwater is built determines the new direction of the waves (after they've hit the breakwaters), and in turn the direction that sediment will flow and accumulate over time. Environmental effects The reduced heterogeneity in sea floor landscape introduced by breakwaters can lead to reduced species abundance and diversity in the surrounding ecosystems. As a result of the reduced heterogeneity and decreased depths that breakwaters produce due to sediment build up, the UV exposure and temperature in surrounding waters increase, which may disrupt surrounding ecosystems. But as a kind of environmental friendly breakwater,