Catastrophic winter flooding will increase with climate change unless we substantially change the way we use land

Ian Carey News, Press Releases

The Environmental Pillar is calling on the government to bring in substantive land use changes to protect communities from increasingly frequent high rainfall events.

The restoration of wetlands, bogs, native woodlands, and hedgerows can play a hugely important role in both preventing flooding and dealing with climate change.

Just two weeks ago the Environmental Protection Agency (EPA) released their latest report on the impact of climate change on Ireland.

It outlined how ‘heavy rainfall events are projected to increase during winter and autumn’ and how the frequency of storms will decrease but their intensity will increase.

If we do not deal effectively with climate change and land use in Ireland, the best information we have suggests we will continue to see very damaging annual flooding in our towns and cities.

‘Fortunately the same measures we need to bring in to deal with climate change can also help prevent flooding as they slow down water on land,’ said Theresa O’Donohoe, Convenor of the Climate Change working group of the Environmental Pillar.

‘The effective use of habitats such as wetlands, bogs, native woodland and hedgerows also play an important role in protecting biodiversity which is under threat from any land use change.

‘Without a doubt one of the most important measure the government should look at is rewetting our peatlands. Our bogs, if restored, could hold substantial volumes of water and contribute to flood relief. But importantly it would turn our peatlands from net carbon emitters to carbon stores.’

Andrew St Ledger, Convenor of the Tree Cover Working Group of the Environmental Pillar added:

‘Appropriately sited native woodlands especially in the uplands in tandem with upland bogs could help slow down floodwater and ease the flooding risk as well as contributing to carbon sequestration and protect wildlife. Clear-felling of trees must be phased out in favour of continuous cover small felling coupe practices. This negative practice of industrial clear-felling leads to soil erosion and compaction caused by the use of heavy machinery creating impermeable pans. When this is combined with the prevalence of deep vertical forestry drains, it results in the rapid run off of storm waters from our vulnerable uplands as well as the silting up of streams and rivers, by the tearing of the banks. The place to target flooding is in the uplands where there is an opportunity to soak up as much of the rainfall as possible before gravity takes it down to the lowlands with catastrophic results when left unchecked. ‘

Measures to protect communities from flooding

1. Ecosystem restoration – Incentives need to be given of the restoration of marshesand wetlands that can obviously act as a buffer during heavy rainfall events. Peatland restoration, native woodland and the development of hedgerows in catchments to slow down water and reduce sediment runoff. These natural defences are cheaper and more effective than the current hap-hazard strategy of building more flood defences which can simply move the problem elsewhere.
2. Integrated river catchment management approach – Policies must look at the entire catchment area of watercourses and promote a coordinated framework for the development, management and conservation of water, land and related resources. Local flood protection measures can have negative effects both downstream and upstream. Therefore, it is important to take the whole river basin into account.
3. Sustainable Flood Management techniques like soft engineering are an absolute necessity. Wetlands have an essential role to play in helping us deal with these events. Hard engineering solutions are not always the answer. The movement of water through a catchment needs to be slowed down so that rivers are not overloaded by rapid drainage.

Notes to the editor

1. EPA report available here.
2. Native woodlands can play an important role in absorbing water. They create loam soil which is composed of one quarter water, one quarter air, and one tenth organic matter. When it is compacted and degraded it loses its ability to hold water. Loam soil is created from the leaf dropping in autumn, the water seepage by tree roots and the relationships with insects and fungi constantly breaking down organic matter into minerals and nutrients. It is this seepage ability to absorb large volumes of water in the leaf litter and the root sponge area around native trees bases that regulates water, what the tree does not need is stored at its base and slowly released through a system of sieving creating a network of small tributaries which checks too swift surface evaporation, thus slowing down the water .The same argument is being made in the UK by George Monbiot, regards the importance of trees in our uplands and the futility of spending millions on inadequate flood defences in the lowlands. Click here.
3. An EU report from 2012 concerning forests and climate states,” River engineering works and reservoir building have had very little effect on flood frequency “. Click here.
4. A US study ” How Trees Can Retain Stormwater Runoff – USDA – Forest “, found trees in urban areas can cause a reduction of between 2 – 7 % in flooding volumes. Click here.

Ian CareyCatastrophic winter flooding will increase with climate change unless we substantially change the way we use land