Great explanation so the folks can finally understand why we keep getting 100-year events every 6-8 years.
Also (touched on at the end) is why insurance losses are getting bigger and bigger. well, if a Hurricane hits an undeveloped coast and nobody was there, was it really ever a storm? Otoh, if a Hurricane hits a new development on the Outer Banks and 96 new homes get turned into firewood, then "Billion dollar losses from Hurricane William" will be the headline.
I think that when people talk about 100-year floods they are abusing terminology. In urban planning 100-year flood line maps are used to indicate the risk of flooding of specific properties, given specific precipitation levels. The rise of running water levels, ie, runoff, during a rain storm, in an urban environment depends on the precipitation on given areas, as well as the paving of those areas. By paving I mean any structure that does not absorb water, eg, rocky outcrops, roofs, roads, parking lots, paved lots, etc. The paving in an urban area usually increases as an area is developed. Often the storm water drainage system is not adapted to accommodate the expected increase in runoff due to new buildings, and roads. Its become popular to blame the resultant increase in the risk of flooding on global warming, which is of course incorrect. The lax management of the built environment is to blame.
Great explanation so the folks can finally understand why we keep getting 100-year events every 6-8 years.
Also (touched on at the end) is why insurance losses are getting bigger and bigger. well, if a Hurricane hits an undeveloped coast and nobody was there, was it really ever a storm? Otoh, if a Hurricane hits a new development on the Outer Banks and 96 new homes get turned into firewood, then "Billion dollar losses from Hurricane William" will be the headline.
I think that when people talk about 100-year floods they are abusing terminology. In urban planning 100-year flood line maps are used to indicate the risk of flooding of specific properties, given specific precipitation levels. The rise of running water levels, ie, runoff, during a rain storm, in an urban environment depends on the precipitation on given areas, as well as the paving of those areas. By paving I mean any structure that does not absorb water, eg, rocky outcrops, roofs, roads, parking lots, paved lots, etc. The paving in an urban area usually increases as an area is developed. Often the storm water drainage system is not adapted to accommodate the expected increase in runoff due to new buildings, and roads. Its become popular to blame the resultant increase in the risk of flooding on global warming, which is of course incorrect. The lax management of the built environment is to blame.
Exactly. The old-school and proper use meant "flood of a certain size."