Flood level
Flood level can be defined as the height reached by a body of water (such as a stream or river) resulting from overflow beyond its normal limits.
A high flood level is the maximum level to which a body of water could rise due to rainwater and runoff during a flooding event. High flood level calculations take into account local conservation or reclamation efforts supported by artificially constructed measures such as water storage tanks. High flood level information for a specific site can be used for planning purposes to help determine a design flood level.
A design flood level is defined in Home Quality Mark One, Technical Manual SD239, England, Scotland & Wales, published by BRE in 2018. It is described as a historic or notional flood event of a given annual probability, against which the suitability of a proposed development is assessed and mitigation measures, if any, are designed to accommodate a storm event. This includes an allowance for climate change in line with current best practice national planning guidance.
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