Barrier Breaching Processes and Barrier Spit Breach, Stone Lagoon, California

To appear: Shore & Beach, Vol. 70, No. 4, 2002.

Barrier Breaching Processes and Barrier Spit Breach,

Stone Lagoon, California

Nicholas C. Kraus

U.S. Army Engineer Research and Development Center

Coastal and Hydraulics Laboratory, 3909 Halls Ferry Road

Vicksburg, MS 39180, Nicholas.C.Kraus@erdc.usace.army.mil

Adele Militello

Coastal Analysis, LLC, 4886 Herron Road

Eureka, CA 95503, CoastalAnalysis@cox.net

Gary Todoroff

Datamaster Designs, 618 F Street

Eureka, CA 95501, DataMaster@NorthCoastPhotos.com

ABSTRACT

Review of the literature of barrier island and barrier spit breaching reveals there is a paucity

of information on the physical processes beyond qualitative reporting of case studies, despite the

significant potential environmental and societal consequences that unintended breaches can

bring. A breach susceptibility index is introduced to classify breaching potential by storm surge

or equivalent inundation mechanism. A recent breach of the barrier spit enclosing Stone Lagoon,

located on the Pacific Ocean coast, Humboldt County, northern California, provides background

for the discussion. The spit is believed to have breached seaward between March 13 and 15,

2002. Aerial photography was flown four times at approximately weekly intervals from March

18, documenting breach closure, movement of the ephemeral ebb shoal, and initial recovery of

the barrier spit.

Additional Keywords: Barrier islands, inlets, Humboldt Lagoons State Park, Big Lagoon,

Mecox Pond, Little Pikes Inlet, overwash, storm surge

INTRODUCTION

In a coastal context, a breach is a new opening in a narrow landmass such as a barrier spit or

barrier island that allows water to flow between the water bodies on each side. Breaching can

occur naturally or be artificially induced, and it can have positive or negative consequences.

Coastal ponds, lagoons, and blocked river mouths are sometimes breached purposefully and,

usually, temporarily. Common reasons for induced breaching are: (a) to reduce water level in

the water body that might cause flooding of neighboring property; (b) to decrease or to increase

salinity in the lagoon or bay, depending on the situation; (c) to promote water exchange or

flushing for improving water quality; and (d) to facilitate migration of marine organisms.

Photographs in Figure 1 were taken several hours after a breach was cut by backhoe at Mecox