Slides in this set
This strategy aims to reduce the possibility of flooding by managing land
It includes a range of methods which try to avoid excessive runoff
· Afforestation slows down the rate at which water reaches a river.
· Contour Ploughing which reduces the amount of surface runoff and
therefore, reduces the chance of a flood.
· Allow farmland to return to marshland and allow river to meander.
· Near-continuous cover for example winter green manures to reduce
runoff and soil loss.
·Reduce the amount of sediment washed into the river channel
·Restore backwaters to accommodate flood water.
Afforestation requires substantial areas in the catchment to plant trees.
These increase interception storage, evapotranspiration, help reduce
runoff and hold the soil together in the river channels to reduce silting.…read more
Afforestation can prove to be an effective method, but it requires large
areas of land, and time for the trees to mature and forests to become
Contour ploughing means increased water infiltration which promotes
better water quality. Also, it increases soil retention which encourages
root development, binding the soil and preventing erosion.
Ploughing at right angles to the natural slope of the land creates a series
of stepped ridges but it may hinder modern farming.
Afforestation Contour ploughing
upstream on the in the Gina River
River Exe catchment…read more
This strategy intends to reduce floodplain development. Predictions about the
extent of future flood events can be made using records of historic flood
events. Return periods of different magnitude can be linked to the areas of the
floodplain that are likely to be affected therefore zones of relative risk can be
· Zone A: Prohibitive Zones- these are areas nearer to the channel with a
moderately high risk of flooding. Waterfront developments may be allowed
here but future developments are unlikely to permitted.
· Zone B: Restrictive Zones- little development is allowed, but those permitted
should be flood-proofed. They're more appropriate for low-intensity or low-
value land uses such as pasture, playing fields and car parking.
· Zone C: Warning Zones- these areas are further away and situated on higher
relief which may be used for a wider range of developments, such as residential
and public buildings. Inhabitants are warned of imminent flood risks and told
how to react when they occur.
All these planning aims must be understood in the light of future developments
as various historic riverside settlements can't be resited.…read more
Zoning can be used to reduce damages from flooding and be flexible
enough to recognize that other forms of land use are compatible. It's also
low cost for undeveloped areas of floodplain. A major flood event is
sometimes an opportunity to correct the planning errors of the past.
Removal of flood-prone development and conversion of the land to a
conforming use is an option to consider. Existing floodplain damages are
not reduced and industries may have to move elsewhere.
It is important, however, to ensure that the supporting infrastructure such
as buildings and houses are located away from the flood-prone area or are
River Rhine Floodplain
Flood proofing can be permanent or temporary. Buildings can be constructed with flood-proof ground floor
walls or have temporary flood gates built at times of high flood risks. By keeping the valuable and
vulnerable facilities on higher levels and/or that the lower levels are only of a low-value land use like car
parks. This way the potential damage from floods can be reduced. There are three main approaches to
Raising or Moving the Structure
· One technique is to raise the structure in place so that the lowest floor is above the expected level of
floodwaters. This is commonly referred to as "elevation."
· Cost is an important factor to consider in elevating structures. Lighter wood frame buildings are easier
and cheaper to raise than masonry buildings. Not only are masonry buildings more expensive to raise, but
they also are susceptible to cracks.
· Relocation is an appropriate technique in high hazard areas where continued occupancy is unsafe, where
owners want to be free from flood worries. A major concern in evaluating the feasibility of relocation is cost.
Acquiring a new lot, constructing a new foundation, and paying for moving contractors and new
landscaping must be considered. There are several government programs that provide financial assistance
or that acquire floodplain properties.…read more
· Two techniques are employed in constructing barriers. The first technique involves constructing free-
standing barriers that are not attached to the structure. The three primary types of free-standing barriers used
to reduce flood damages are:
· Berms - A berm is typically an earthen structure, constructed from local compacted fill, that stops flood
water from reaching the building. To be effective over time, berms must be constructed out of suitable
materials (i.e., impervious soils) and with correct side slopes.
· Levees - Levees, which are similar to berms, are also earthen structures of compacted local fill. Levees are
usually constructed along riverbanks to prevent the floodwaters from spilling over and flooding structures.
Both berms and levees are generally appropriate for flood proofing a home where floodwaters are less than 6
· Floodwalls Floodwalls are usually constructed out of reinforced concrete and anchored into the ground.
Floodwalls, because of their greater cost, are usually not used to protect homes.
Berms Levees Floodwalls…read more