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Harris County Sheriff’s Deputy Rick Johnson pauses to listen for people’s voices as they search for people in a neighborhood inundated after Hurricane Harvey by water from the\u00a0Addicks Reservoir, Wednesday, Aug. 30, 2017, in Houston.\u00a0<\/p>\n
Jon Shapley\/Houston Chronicle<\/p>\n
When Harris County officials shared drafts of the area\u2019s new FEMA flood maps<\/a> in February, flood experts said they were long overdue<\/a> \u2014 but could also quickly become outdated.<\/p>\n \u201cWe have known for a long time that our 100-year floodplain was in error,\u201d said Jim Blackburn, an environmental lawyer and co-director of Rice University\u2019s SSPEED center. He added that the Houston region has continued to build based on flood maps that haven\u2019t been updated in years.\u00a0<\/p>\n The maps define high-risk flood zones by putting individual plots into categories: Floodways, 100-year floodplains and 500-year floodplains. Floodplains are defined by whether the areas have at least a 1% or 0.2% chance of flooding each year, and can impact insurance requirements<\/a>.\u00a0<\/p>\n Article continues below this ad<\/p>\n But experts such as Blackburn warn that while the new draft flood maps do a better job than previous versions illustrating the area\u2019s current risks, they are poor predictors of the future.<\/p>\n \u201cEven with these expanded maps, they’re still just capturing the tip of the iceberg,\u201d said Jim Elliott, a Rice University sociologist who specializes in flood risk.\u00a0<\/p>\n SEARCHABLE MAP: Is your Houston home outside of the floodplain? New research says think again.<\/a><\/p>\n Elliott explained that the draft FEMA maps rely on Houston-area data from the past few decades, excluding extremes that are difficult to model. This strategy, he said, imagines risk through \u201ca rear view mirror\u201d and leaves out future projections for rapid development and climate change.<\/p>\n Article continues below this ad<\/p>\n \u201cWe\u2019re still looking backwards,\u201d he said.<\/p>\n Underestimating flooding is risky at a moment when, for coastal Texas, factors like climate change are \u201cloading the dice in favor of more frequent and severe floods,\u201d said Natural Resources Defense Council environmental attorney Joel Scata.<\/p>\n This tension between what regulatory maps say and Houstonians\u2019 true risk can leave residents with \u201ca false sense of security,” co-director of Rice University\u2019s Center for Coastal Futures and Adaptive Resilience Dominic Boyer said.<\/p>\n Here are key things to know about the new maps \u2013 and what they leave out:\u00a0<\/p>\n Why did FEMA update its floodplain maps?<\/p>\n By law, FEMA is required to review or revise its county-by-county flood maps every five years. In practice, it happens far less frequently. Harris County\u2019s last comprehensive update was in 2007.<\/p>\n Article continues below this ad<\/p>\n Since then, local authorities have realized how poorly the 2007 maps reflected rapidly-changing flood risk in the area. Over just three years, from 2015 to 2017, the region had three 500-year storms, culminating in Hurricane Harvey.\u00a0<\/p>\n According to the Harris County Flood Control District, the pattern of extreme weather made it \u201cclear that existing floodplain maps were not fully reflecting flood risk,\u201d and the county started working with the federal government to design new maps.<\/p>\n What do the draft FEMA maps tell me about my flood potential?<\/p>\n The updated maps from FEMA, once enacted, will impact households by requiring many more Houstonians to buy flood insurance. But researchers and local officials have said for years that the maps should not be necessary to prompt coverage; rather, everyone in Harris County should have flood insurance.\u00a0<\/p>\n Once finalized, the FEMA maps can also be used as a basis for building codes, and were originally designed to dissuade people from developing or living in the county\u2019s most-risky plots. Instead, experts say, they are often looked at through the lens of financial harm.<\/p>\n Article continues below this ad<\/p>\n \u201cPeople assess the risk more as a risk of their insurance premiums going up than as a risk of actually flooding,\u201d Elliot said.\u00a0<\/p>\n What is different about the maps this time?<\/p>\n In a June public session on the FEMA update process, the flood control district\u2019s Planning Division Director, Ataul Hannan, said the newly drafted maps \u201cgo way past just a routine update.\u201d<\/p>\n \u201cThe most significant driver of this study is that rainfall amounts are also increasing,\u201d Hannan said.\u00a0<\/p>\n Officials included new federal data that indicates a 30% increase in rainfall. The draft maps also incorporate nuanced topographic data and account for the benefits of new flood control infrastructure.<\/p>\n Article continues below this ad<\/p>\n INSURANCE COSTS: How much does FEMA flood insurance cost in your Houston neighborhood? Search our map to find out.<\/a><\/p>\n But Houston-area experts have cautioned that other factors, including future impacts from the changing climate, were not reflected in the maps.\u00a0<\/p>\n Why don\u2019t FEMA flood maps consider climate change?<\/p>\n FEMA is required to create regulatory maps based on the rainfall and storm data from the past several decades, using this historical information to predict the statistical likelihood of future outcomes. Increasingly, climate researchers are arguing that the world is changing too quickly for these techniques.<\/p>\n \u201cClimate change is suggesting that the models of the past and the data of the past are mostly inadequate,\u201d Rice\u2019s Elliott said. \u201cThat backward casting isn’t working as effectively as it used to.\u201d<\/p>\n