What is Afforestation?

Afforestation is the opposite to deforestation, and is the planting of trees in an area of non forest land.

(Trees have been planted on the left bank of the river, and around the reservoir)

Advantages

Afforestation creates a habitat for wildlife along with being a more visually pleasing method of flood management. The tree roots decrease erosion as they compact and stabilise the soil, this means that less soil is carried by surface runoff and through flow into the river, reducing the channel capacity. Another advantage of Afforestation is that once fully grown, the trees are self sustainable, which means that they do not require a lot of attention and do not need to be as looked after as a hard engineered material. Afforestation is relatively cheap compare to other flood management schemes, especially those of hard engineering.

Disadvantages

However, this method does not prevent flooding, but just reduces the severity. Due to the reduction in erosion, this makes it more difficult for the river to build up natural levees as a result of the lack of sediment. This means that the river is actually more likely to flood in the future unless other methods are used alongside Afforestation. Another disadvantage of Afforestation is that it takes a long period of time for the trees to grow into adults, causing a long wait for the trees to be used to maximum potential. Afforestation requires alot of labour in planting all the seeds and ensuring the growth of them.

How does Afforestation cause a long lag time?

Afforestation means that there are more trees encouraging more interception. The water that is intercepted can then be either absorbed and held as vegetative storage or evaporate off the leaves via evapotranspiration. This means that less water gets chance to infiltrate and reach the river through throughflow and ground water flow or through surface runoff. The roots also provide structure for the soil making it more difficult to infiltrate. All these factors lead to the long lag time, as afforestation reduces the amount of water reaching the channel and how fast it reaches it.