Static or Dynamic? What is Your Planning Model?

by Randy D. Bosch

Do You Have a “Plan”? 

We are all working toward goals under someone’s plan – one adopted personally, by their business, or by the community. Most people claim to have, and some may actually have, a “Plan” for their business, work, personal and family life, or community. For some the plan is “Play it as it lies”!

As you read the following summary of planning models for American flood zones and flood plains, use the explanation to think about Planning Models you use by choice or impostion.

Flood Prediction? Prevention? Mitigation? –“We Have a Plan”

Flooding from raging rivers bursting through banks and levees, exacting high tolls of life and property, are world-wide problems. The United States has agencies, standards, public works and Planning Models to help predict risks and mitigate impacts where possible. Similar effort occurs world-wide.

Venezia - Acqua Alta (c)2006 Randy D. Bosch

For centuries Venetians have managed the Venetian Lagoon, even diverting rivers around it to reduce the risk of flooding.  Now, the primary risk is from the sea, exacerbated by human activity that has damaged the physical condition of the Lagoon.  Conditions change – Time for Plan B?

Several engineering models exist for determining the extent of Flood Zones and Flood Plains along most streams and rivers in the United States, the Static Model and the Dynamic Model being most prevalent.  Here is a brief  “non-engineer” interpretation of each model:

Static Model

This model, widely used nation-wide for several decades, assumes that the river in question has levees or banks on both sides at a particular point. To determine the extent of likely flooding under 10-year or 100-year frequency conditions, take a cross-section of the river and adjacent topography at a study point, draw a horizontal line across the top of the levees and extend it until it hits higher topography. The land within that area is predicted to be subject to flooding.  The straight-line approach assumes vast amounts of water outside the levee in many areas, to represent what might happen as the river flood flows continue from upstream.   Repeat the exercise at intervals up and down-stream, draw a map, inform landowners and agencies of the extent of the predicted flood area, then plan improvements or restrictions to prevent or mitigate damage.

The problems are obvious – rivers are dynamic. Break-outs commonly occur up-stream due to overflow, surges, wave action, scouring, bank failure or obstacles (often man-made) diverting the water out of the normal streambeds – sometimees the entire flood flow.  The Static Model is, well, static and does not take dynamic conditions into account. Those also include sidebank erosion, channel changes, and back-eddy flooding.  

Despite such challenges, that Model represents the best available science and thinking of its time.  Its use has certainly saved many lives and reduced property losses.  Government and communities applied lessons learned from its use, and worked to find a better technique, something more dynamic.

Dynamic Model

The newer, far more expensive to apply, Dynamic Model still uses cross-sections and topography, but more extensively includes analysis of actual water flow and effects upstream from a study location. When applied to the best degree possible within its design science and mathematics, then overlaid on a Static Model flood map, some areas that the Static Model predicted to be flooded are shown to above flood level, while other areas it did not predict to be flooded are now shown to at risk.  Public agencies continue to work on improved versions of the Dynamic Model, learning from experience and from improved information gathering technology.

The Models have a great effect on public infrastructure and private property owners, including on the ability to finance construction. Obviously, financial institutions are less willing to finance improvements that may be damaged or destroyed. In many areas, government mandated “flood insurance” must be purchased to secure financing, areas where homes or businesses can be built are limited, and costly flood protection improvements built into permitted structures in danger of fairly limited flooding.

In some cases, mapping has impelled construction of levees on one side of a river, to protect property on that side, but they may also divert high flows across the river where there has not been flood danger or damage in the past. If a model (either model) is misapplied or physical conditions changed have changed, the risk of unintended consequences and collateral damage increases. 

Glen Canyon Dam (c)2009 Randy D. Bosch

The models cannot help predict how unusual events far upstream (e.g., dam releases necessary to prevent failure) add to flood conditions downstream, because those events are unpredictable! The River and the weather have lives of their own! Multi-year rainfall and run-off, 100-year storms, snowpack melt rates and the like use “averages” and historical extremes.  A “Black Swan” combination of extreme and unusual events at one time can obviously lead to greatly increased flooding, loss of life and property damage. 

There may be a better way than those Models to help fallible humans assess risk of flooding, but they represent the “state of the art” until improved. State and Federal agencies are thankfully working on improving them , yet funding of the work let alone subsequent modifications to land use and prevention implementation takes decades to implement, at best.

Back to YOUR Plan

As you have read this brief summary, have you thought about YOUR planning models for business, personal goals and community goals? Are your models Static – based upon understandings you gained in the past, without continued review and improvement based upon newer information, newer technology, more appropriate relationships to needs, demands and resources? Or, are your models Dynamic – taking the best information from the old Static models and applying what you have or can learn to make your planning more broadly based, using up-to-date “real world” constraints, resources and opportunities to be responsive to changing and sometimes hard to predict conditions?

Next: “Domesticating the Unknown”

How do your Models plan responses to unpredictable “Black Swans”?  Nassem Nicholas Taleb, author of the seminal works Fooled by Randomness and The Black Swan, states,

“I am interested in a systematic program of how to live in a world we don’t understand very well –in other words, while most human thought…has focused us on how to turn knowledge into decisions, I focus on how to turn lack of information, lack of understanding, and lack of “knowledge” into decisions –how not to be a “turkey”…”The Black Swan (and the 4th Quadrant papers) drew a map of what we don’t understand…my current work focuses on how to domesticate the unknown “what to do in a world we don’t understand”.

Visit his website at for a great deal of information on the two books, other publications, and his ongoing work.

Next, actively work on those planning models – Static, Dynamic, or something innovative that includes “how to domesticate the unknown” in YOUR work, life and community?  Then, since a plan does not work without including all of the stake-holders and everyone else affected by its use and potential results, to increase the chances of your Plan’s success:

Share what you find out with us!


About randysrules

From a professional background in architecture, community and regional planning, urban design, leadership, and fine arts, this blog provides insights on ethics, leadership, architecture/planning/urban design, Venice, and whatever intrigues me at the time. Enjoy!
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