The 30 local governments in our area each have their own stormwater policies and drainage systems that can vary widely between jurisdictions, even though they are often dealing with the same water flowing across parts or all of them from the same storm.
This gives rise to a high degree of uncertainty about flood risk and what to do about it. Currently, our decisions are subjective and usually uninformed about the threats. This also explains why so few of us followed the latest evacuation order and will do so in the future.
We all have a silent individual flood protection plan that is full of holes. Lacking is the explicit water volume expressed in inches of rise of storm surge and/or inches of downpour during a 24-, 48- or 72-hour period or rise in upland river flows coming down at us. Most complex to estimate are variable intensity hurricanes with all three water sources together simultaneously impacting the Lowcountry.
Simply put, water comes in at us from three directions: up, down and sideways. Much more needs to be thought about and developed into a coherent large-scale county flood protection that will have a design criteria, call it X, expressed in units of water volumes derived from the three water sources and hurricane intensity.
Use of historical and projected water volume data is flowed across the land using mathematical models to indicate the areas that stay dry from the three source volumes. This is the current level of flood protection and is highly variable across the land. It is best understood as a flat ruler that attaches to our homes that lets us know if my shoes are still dry or that water is ankle-high, knee-high, over my car tail pipe or over my head. Calculating our individual flood impact values will reduce the uncertainty and guide us to better decisions for our families.
Right now, we all have an unspecified and different flood risk at our door sill and no municipal flood protection plans that have a design criteria.
Hodgepodge-lodge describes our current flood protection. County Council needs to put the engineers to work to explicitly specify the level of protection our residents are provided with or without a sea wall and begin improving the in-place protection over the decades ahead. Funding this needs to be our highest community priority if we are to live here.
Instead, we have silence about the Swiss cheese of county flood risk but are represented by a County Council majority willing to commit our present and future county treasury to building the I-526 of uncertain cost, sucking up all the available funding that we need to now put up between now and 2030 without delay.
Building this highway will exacerbate the damage by giving residents the false impression that it is possible to build into areas, that by the water’s volume, it is not possible to protect from flooding, i.e., Johns Island where the completion of I-526 is proposed. A flood protection plan that works at X is about physics, subject to errors of estimation. It is not about beliefs or political dogma or a highway.
Fred Palm of Edisto Island is a retired professor of oversight and investigations at the John Jay College Graduate School of Public Management and a former executive director of the Association of Inspectors General.