What are some examples of hard vs. soft engineering?

Hard engineering manages coastal zones in order to protect high-value areas from flooding or falling into the sea through erosion. These structures are usually high-cost and short-term. 

Examples include a sea wall, which will be strong to protect, e.g. a town, but will crumble eventually, is expensive, and requires expensive maintenance. It additionally doesn't absorb any wave energy, so the waves continue to erode the wall. Groynes collect material swept away through long-shore drift, building up the beach which acts as a defense and as a draw for tourists. These, however are also costly and expensive to maintain. 

Soft engineering is low-cost and long-term. However, it does not protect against flooding as well as hard engineering and therefore is generally used in areas which have high biodiversity or are low-cost, i.e. there is no farmland or houses. 

Examples include building up the beach material as it is swept away. This doesn't require building groynes, so it is cheaper, and it's good for tourism. However, it requires constant work to build the beach back up. Natural material may be planted, e.g. reeds or trees, to stabilise banks. These are also a cheaper option but they take a long time to become effective and some flooding must still be allowed.