GONZALES — Parish consulting engineer Michael Songy concluded Thursday that a new parish analysis of the August flood suggests the parish’s elevation standards for new construction are sufficient for much of the parish.
But pressed by some council members about parish flood mitigation rules, Songy also acknowledged that to avoid flooding in the parish’s lowest areas, it might be worth looking at requiring builders to elevate homes on piers or try other home-raising methods that don’t require dirt.
Songy warned, however, that such rules would have to apply equally across a region or a subdivision so that all homes follow them and some are not later allowed to build on slab homes raised with dirt.
“I certainly think it can be done, but it has to be done globally with an entire area or an entire development. Based upon what I’m seeing here, yes, I think there’s merit to that discussion,” Songy said.
Songy offered the assessment at a council workshop as he presented a new analysis of the August flood in Ascension and how high the water got.
Louisiana State Climatologist Barry Keim also spoke to the council about the weather system that dropped all the rain that resulted in the flooding. Keim said rain in some areas north of Ascension Parish “grossly exceeded” what would be expected to fall in a 1,000-year rainfall event, or a rain that has a 0.1 percent chance of happening in a given year.
Councilmen Todd Lambert and Benny Johnson used the analysis’s findings to raise questions about how the parish requires developers to account for the flooding impact on mounds of dirt used in new construction.
The fill and other drainage development rules prove controversial because residents often blame the fill required for elevation of new homes for neighboring drainage problems.
The August flood has been no exception, but Songy, as many parish officials and developers have in the past, defended the rules because no dirt can be imported into a new project and detention ponds must be built to account for the lost drainage storage capacity created by development.
Stirring the question about the elevation policies was Songy’s new flood analysis, which compiled a variety of data to come up with flood elevation measurements across the parish.
The analysis found that, with the exception of a limited area which roughly corresponds with the St. Amant and Lake areas near the Amite River, water levels matched within a foot to what would have been expected in a 100-year flood.
But, in the St. Amant and Lake areas of far eastern Ascension, flood water rose up as much as 2 feet higher than the predicted height of the 100-year flood.
“I think the fact that if water got pretty well right to the 100-year (flood elevation) and you’re asking them to build their structures 1 foot above, I think, you know, that’s certainly appropriate,” Songy said of the elevation standards.
When Songy offered his take on the parish elevation standards, he noted an exception for the St. Amant and Lake areas.
Parish standards require new homes be built 1 foot higher than the elevation expected in a 100-year flood, which is a flood that has a 1 percent chance of happening in a given year.
Questioned later, Songy said his firm did not yet know why those areas of St. Amant and Lake saw much higher water but are a topic for further study.
The 100-year-flood is deemed the benchmark risk level on federal flood insurance rate map. Those within the 100-year flood plain must have flood insurance on their homes if they have bank loans.