Shoreline Protection – Honorable After All

by Don Flora (a real scientist)

Six months ago I summarized “science” doctrine about bulkheads,  all of which declared bulkheads bad for the environment.  I ask, “Where is the research?” and “What are the numbers?”

Lo and behold,  I hadn’t noticed a lot of existing numbers.  They come from shoreline inventories conducted by Bainbridge Island and Kitsap County.  The inventories included human-built “stressors”  like docks and bulkheads,  plus natural habitats including eelgrass beds,  forage-fish spawning areas,  and the extent of seaweed and kelp. 

These things were tallied for each of the hundreds of beach reaches around eastern Kitsap and Bainbridge Island for which data was available.  Then a consulting firm combined the data in various ways to develop,  for each shoreline reach,  an index number intended to summarize habitat welfare in each reach.  

At this point one could look at whether,  say,  bulkheads are associated with low-grade habitats.  See the graph below,  in which each dot reports a reach’s situation.  Dots toward the left are reaches with little shore protection.  If those leftward dots are high on the graph they reflect a high degree of habitat welfare.  


Click image to enlarge.

Shoreline doctrine says that the cloud of dots follows a narrow path from upper left to lower right.  But notice that the dots are high and low all across the graph.   The cloud is scattered,  not compressed, indicating a low correlation between bulkheads and habitats.  The graph suggests that bulkheads are neither good nor bad for habitat.  Habitats apparently respond to other factors in the environment. 

The graph is for Bainbridge Island. East Kitsap’s has the same pattern but with fewer dots because there is little data on habitat in the Kitsap assessment.  The visual conclusions were confirmed when I did mathematical analysis of the same data,  using common statistical methods including regression analysis.

Specifically,  for both easterly Kitsap and Bainbridge Island the correlation between bulkheads and habitat is not significantly different from zero.  The regression analysis indicates that neither an increase nor a decrease in shore protection is associated with habitat change,  at least within the range of the bulkhead coverage found on the ground.  

More detailed analysis showed there is no evidence of a statistically valid relationship between reaches’ bulkhead length and eelgrass welfare,  overhanging vegetation extent,  nor forage-fish (surf smelt and candlefish) spawning-ground expanse.  In short, bulkheads play a statistically non-significant role in near-shore habitat welfare.  

Is this important?  You bet.  It means that three key foundations underlying the new shoreline plans have no relevance for bulkheads.  Those three basic drivers are: 

NO NET LOSS The computations show that bulkheads are impact neutral. There is neither gain nor loss associated with removal or addition of shore protection. 

RESTORATION Removal of bulkheads will not generate better habitat. 

CUMULATIVE EFFECTS Without effects, even across the broad reaches and the whole aggregate of reaches, there is nothing to accumulate.

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