This post continues our ongoing series on extreme weather; and the varied ways in which municipalities throughout the country have handled recovery and future preparations.

In August 2017 Hurricane Harvey, the year’s deadliest storm, hit Texas as a Category 4 hurricane. Harvey tied in rank with Hurricane Katrina as the costliest tropical cyclone on record with $125 billion in damage, largely due to flooding in the greater Houston area. Lost revenues to retailers and restaurants in the Houston area alone were estimated at nearly $1 billion (according to reporter Adrianne Pasquarelli). Houston, the fourth largest city in the nation, has grown rapidly -- having built on, over and near various wetlands and drainage areas. Unlike “Superstorm Sandy,” which was a combination of rain and wind, Hurricane Harvey’s damage was caused by the enormous amounts of rain to fall within a relatively short period of time. In fact, according to the National Weather Service, Harvey produced between 20 and 40 inches of rain in a five-day period in the greater Houston area, with Cedar Bayou (28 miles east of downtown Houston) reporting 51.88 inches of rain during this time. Some estimates have translated the rainfall into more than 15 billion gallons of water which, combined with the reduced wetlands, resulted in more than 440 miles of land being underwater. These totals were so high that the National Weather Service added two new colors to its rain index. Following mandatory evacuation of portions of the area, levees were breached and the Army Corps of Engineers began controlled water releases for two reservoirs in an attempt to manage flood levels.

County and city measures after Hurricane Harvey

As New York and New Jersey did following Sandy, the state of Texas invited interested homeowners to volunteer to sell their property to the government. While Harris County has had a Flood Control District for more than 80 years, the district reportedly received more than 3,000 voluntary requests for buyouts following Hurricane Harvey: more than the total number of buyout requests for the decade prior to Harvey’s arrival. While Houston has no “zoning code,” as it is known in New York, there were building regulations in place.  Prior to Harvey, homeowners in a 100-year floodplain were required to build one foot above that floodplain.  (A 100-year flood is any flood event that has a one percent probability of occurring in any given year.) Within seven months of Harvey’s aftermath, the Houston City Council approved changes to its floodplain regulations requiring that new homes being built within the city’s 500-year floodplain be built two feet above that floodplain. (500-year floods have a 0.2 percent chance, or 1 in 500 chance, of occurring in a given year.) According to the City, 84 percent of homes in the 500-year floodplain would have avoided damage from Harvey had the regulations been in place prior to the hurricane. Almost one year to the date after Hurricane Harvey, residents approved a $2.5 billion bond package to fund from a potential list of more than 230 projects for flood mitigation and flood prevention.  In addition to the $2.5 billion, Harris County will have access to up to $2 billion in federal matching funds. The bond package passed with support of nearly 85%, which was reported as one of the highest passing percentages of all time in Harris County.  The bonds will not be sold all at one time; rather it is expected that bonds will be issued over the course of at least 10 to 15 years, to finance multiple projects as needed.

Flood planning and mitigation

While no municipality can likely plan for so much rain over a short period of time, the City of Houston and Harris County have taken steps to mitigate future damage from a hurricane. Among the proposed improvements in the bond package, approved by Houston voters, are:

• $1.2 billion for channel improvements
• $401 million for detention basins
• $242 million for floodplain land acquisition
• $12.5 million for new floodplain mapping
• $1.25 million for an improved early flood warning system
• $500 million unallocated, potentially providing flexibility for its uses

Unlike much of New York state, which is still undergoing review, assisting Houston and the larger Harris County since Harvey is the Federal Emergency Management Agency (“FEMA”) flood map updates.  While only portions of the City of Houston and Harris County flood maps have been updated, this information may further assist the city and county in identifying which of the proposed improvements will best assist in flood mitigation.  As noted in a prior post about FEMA’s efforts to update flood maps due to funding constraints, FEMA can only study or restudy a limited number of locations every year.  When FEMA’s updated flood maps are completed in New York, similar mitigation measures may assist municipalities to identify initiatives along the more than 500 miles of coastline and possible properties in the more than 48,600 square miles of land in New York state.