City officials are currently working on updates to Denison’s Flood Damage Prevention Ordinance, which presents guidelines for development about how to prevent flooding issues at the site and further downstream.
“Our goal is to reduce the probability of flood damage happening around our drainage areas,” City Manager Jud Rex said on Thursday, referring to drainage ditches, culverts and other features designed to handle runoff from storms.
Rex said conversations about the prevention ordinance started late last year and that the storms of 2015 played a part in the city’s decision to begin the process. In recent years, Rex said he has seen an increase in “100-year floods” impacting areas that normally do not flood. Flooding last year damaged numerous homes and washed out several roadways. Updating the plan will guide future development in an attempt to mitigate the risk to housing during future flooding events.
“A lot of the flooding that happened last year on Father’s Day wasn’t in a floodplain but was because of poor development near our drainage areas,” he said. Rex specifically referenced a drainage trough running through Easy Street as an example.
In a memo to city staff, Rex said the city is using the services of Birkhoff, Hendricks & Carter to revise the document to meet current best practices in drainage and engineering. A draft document is expected to be presented to the City Council on Monday, and voted on in May, Rex said.
Rex said the goal of the project is to update the ordinance to reflect current conditions in Denison, ongoing development and the newest best practices. For Denison, this includes a recommendation that new development occur one foot above the floodplain rather than simply outside of it, Rex said. These updates to the ordinance will also include hydrology studies for new development to ensure it won’t negatively impact land downstream.
“Any time you add more concrete, more roofs, you add impervious surfaces,” Greater Texoma Utility Authority General Manager Drew Satterwhite said, describing surfaces that don’t easily absorb water.
Within a development, developers typically use detention ponds to hold runoff temporarily and regulate its release. Other, less common methods include the use of underground water storage areas and building materials that absorb water more easily than conventional concrete.
Rex said other concerns going into the design of the document include balancing the need for safety and design standards without placing too heavy of a burden on developers. Currently, developers have been doing their due diligence and have been a strong partner in this initiative, Rex said.
Denison’s current plan is based on templates offered to communities by the Federal Emergency Management Agency following the National Flood Insurance Act of 1968. Rex said it has been “many decades” since the documents have been updated.
“I’d say Denison has done little with its original document since it was adopted,” Denison Public Works Director David Howerton said.
Rex said the work on the prevention ordinance is coinciding with reforms to the city’s Storm Drainage Design Manual, which provides standards and details for drainage feature designs. Rex said this would serve as a companion piece for the ordinances.
“This ordinance alone isn’t going to solve all problems but with our (Storm Drainage Design Manual) it will hopefully prevent most (problems) in our future development,” Rex said.
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