Floods on the Rio Blanco these past few days demonstrate the link to climate change, but not in the way you think.  It was a horrible Memorial Day weekend in Hays County, Texas.  At least three people died from the worst flooding seen since 1922.  The Rio Blanco crested at 43 feet, 30 feet over flood stage.  Over 400 homes were destroyed and the interstate (I-35) was under water. 

The flood warning posted on the San Marcos, Texas website identifies the areas of evacuation.  One area is that in the Blanco Vista neighborhood nearest to the river.  Police officers and firefighters were making door-to-door notifications.

San Marcos (pop. 58,892) is the fastest growing mid-sized city over 50,000 in America according to the latest census data. Literally hundreds of new homes are rising every year.  We took a peek at the zoning paperwork for the latest subdivision in Blanco Vista.  It duly notes that the proposed work is outside the 100-year flood plain.

And there lies the rub.  First, the 100-year flood plain is misleading terminology.  Yes, it is an area that may expect a flood of the kind of magnitude that only occurred once in the last hundred years.  But over the course of a 30-year home-ownership, the likelihood of that occurring is 26%, not 1%

Second, the current flood maps are based on past history.  But climate science tells us that the best information for predicting future flooding is not the past, because the climate is changing. 

So a zoning plan that focuses on the 100-year flood plain may not be particularly helpful.  FEMA is trying to remedy that. It issued its policy statement on climate change in 2012 as an “Agency-wide directive to integrate climate change adaptation planning and actions into Agency programs, policies, and operations.”  That has led to the recently released Federal Flood Risk Management Standard, which seeks to utilize the “best-available, actionable hydrologic and hydraulic data and methods that integrate current and future changes in flooding based on climate science.”  The Army Corps of Engineers has brought climate change into its mapping process. 

Directly on point here are the hundreds of millions of dollars FEMA hands out for flood mitigation projects, which are soon to be linked to climate change.  This could be problematic for Texas, as its governor is on record as vehemently opposed to “the Obama Administration’s liberal climate change agenda.”  What does this have to do with flooding in Texas?  Plenty.  Texas is an eager participant in FEMA funding for flood mitigation, fourth in the nation in its acceptance of $343 million in the last 5 years.

But a large string is about to be attached.  In 2016, FEMA will require climate change to be included in state hazard mitigation planning.  Specifically, “State risk assessments must be current, relevant, and include new hazard data, such as recent events, current probability data, loss estimation models, or new flood studies as well as information from local and tribal mitigation plans, as applicable, and consideration of changing environmental or climate conditions that may affect and influence the long-term vulnerability from hazards in the state.  ($343 million may make a liberal climate change agenda seem a little less liberal and more like common sense.) 

Climate change cannot be established as the cause of the San Marcos historic flooding; a single flood is weather, not climate.  But the flooding is consistent with the predictions of climate change scientists.  We will never know what additional planning and preparation might have mitigated the Memorial Day weekend floods.  But other Texas communities, and elsewhere, may be taking notes.