Articles - GEOLOGIC ASPECTS OF BEACH-FRONT PROPERTY

Beach-front properties in Malibu has as their seaward boundaries a tide line, presumably the mean high tide line established, I believe, in the 1930s, and their landward boundaries along the rights-of-way of a roadways such as Pacific Coast Highway, Malibu Road, and Broad Beach Road. Their main attractiveness is that they afford direct access to the beach and have "white-water" views; however, they also have certain disadvantages. The use of beach-front property in the City of Malibu is subject to a number of more or less serious limitations in terms of both safety and value due to geologic conditions.

MEETING LCP STANDARDS
There are relatively few undeveloped beach-front properties in Malibu. The main problem with developing them is that they must adhere strictly to the Local Coastal Program which has many standards requiring compliance. Developed properties, on the other hand, are not required to "upgrade" to meet the LCP standards except in the case of extensive renovations.

There are essentially three types of developed beach-front property in Malibu: [i] that in which construction is on either a back-shore or a fore-shore or both; [ii] that in which construction is partly on land immediately adjacent to the beach and partly on the beach; [iii] that in which construction is entirely on land adjacent to the beach.

Almost all beach-front property from Las Flores Canyon west to the western end of the Colony, as well as those along Escondido Beach and Broad Breach are type [i]; Most along Pacific Coast Highway east of Las Flores Canyon and along Malibu Road are type [ii]; type [iii] beach-front properties, many of which do not have direct access to the beach because of high sea cliffs, include most along the bluffs from Escondido Beach from Geoffrey's to Paradise Cove, those of Point Dume, some along the western end of Broad Beach, and almost all those from there west to the City boundary.

SPECIAL FOUNDATIONS
Beach-front structures, mostly residences, including almost all along PCH east of Las Flores Canyon and many along Malibu Road west of the Colony, have pile foundations. Those of earlier development were driven timber pilings. Most were simply driven through thin sections of beach sand to refusal and extend, if at all, only a few feet into underlying bedrock. Actually, these older piling systems are nothing much more than braced timber cages resting mostly on bedrock. On their landward sides, the foundations of many are set in road fill simply dumped there in the early days when there was either no building code or none with standards concerning structural fills. Even with these design defects however, such foundations have served remarkably well. The primary problem they now present, other than the occasional need for repairs due to deterioration, concerns remodeling to meet current Malibu LCP and Building Code standards.

SEPTIC SYSTEMS
Along most beaches in Malibu, the sand is moved offshore each winter due to a change in the local wave regime. This can be especially a problem for beach septic systems, almost all of which consist of a standard septic tank and a bulkhead-supported, sand-filled, artificial drain field in which the septic-tank effluent is spread. According to the Ghyben-Herzberg principle, such effluent does mix to any significant extent with underlying intruded sea water. Rather, the effluent flows seaward passing below the bulkhead and then through beach sands or, during periods when sand is absent, directly over the bedrock beach surface. This latter condition may allow pathogens that have survived passage though the drain field to reach the beach. This was the basis of one argument used by Los Angeles County in the 1970s supporting plans for a public sewer system in Malibu.

There have been over the years anecdotal accounts of unpleasant odors from beach septic systems. However, that such conditions have resulted in health problems has never been documented. Furthermore, a study by the U.S. Geological Survey in progress in July, 2009, so far has indicated no pollution problems along beaches where there are septic systems. This calls into question fears routinely expressed by Heal the Bay in justifying its current beach report card program for many locations.

WAVE EROSION AND INUNDATION
The most dramatic safety problem related to all beach-front properties in Malibu has to do with the possibility that a tsunami will occur. The tsunami has long been referred to incorrectly a "tidal wave" possibly because of a certain physical similarity to the tidal bore. A treatment of the tsunami risk in Malibu is presented elsewhere in this web site.

Planning requirements for either new construction or the repair of existing structures at the beach are especially of concern regarding erosion or inundation by waves. These and related concerns are addressed in the City's Land Use Plan (LUP). They are very detailed (LUP, Ch. 4, Sec C, 4.16 - 4.47, pp. 73 - 80. They should be carefully read and understood before deciding to invest in undeveloped beach-front property or developed beach-front property that needs extensive renovation. To some extent, repairs or modifications of existing non-conforming protective structures in developed beach-front properties do not necessarily require point-by-point conformance with the LUP. Nevertheless, careful review is highly advisable. A critique of the relevant LUP sections, in my opinion badly needed, is well beyond the scope of this presentation.

COASTAL LANDSLIDING
The value of Malibu beach-front property is no better demonstrated than the fact that many are developed on or adjacent to landslide debris that could reactivate. In fact, some developed properties are situated on landslides, i.e., moving masses of landslide debris. However, since landslides along the Malibu coast are historically not known to be subject to catastrophic movement, the advantages of beach-front living is seen by many to outweigh the occasional necessity to shim foundations or otherwise correct for occasional structural movements. Beach-front properties in Malibu in or close to landslide areas are those all along Big Rock Beach and Latigo Point, and about 70 percent of Malibu Road is underlain by landslide debris. Those at Big Rock Beach and Latigo Point are intermittently active. A total of about 1,000 feet is active along Malibu Road.

Almost all of the coastal landslides in Malibu are of prehistoric origin. Most have be caused by the effects of ground water in relatively weak bedrock sections where wave erosion has removed lateral support. Also, to an undetermined extent, landsliding may have been initiated or exacerbated by seismic activity. All coastal landslide movements today are a result of conditions not in the beach-front properties themselves but rather conditions in adjacent landward areas. The idea that septic-system effluent in the beach properties themselves contributes to local landslide activity is all but a few is erroneous.

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