San Pareil Accretion Area EarthCache

In geological terms, thirty years is a sliver of time. Yet, in the thirty years that I have come to this beach it has changed dramatically. The most noticeable change has been the significant accretion of land near the posted coordinates, and the transformation of the beach, a bar, and a tidal lagoon area into newly accreted land. This earthcache will discuss how this occurred.

Many earthcaches will take you back thousands or millions of years and describe events that occurred long before any of us (or our ancestors!) walked the earth. This earthcache will teach you about things that have likely happened during your lifetime- and will continue to change further over your lifetime.

If you stood at the posted coordinates about thirty years ago, at medium tide, you could look out towards the northwest and see a bar of sand, gravel and cobble situated approximately where the high tide line is now. This aerial photo, from 1981, shows the bar extending out from the west. As time progressed, the bar formed to connect at both the west and east ends. Inside this bar made for a great swimming spot- at low tide, the water would stay in the lagoon area and warm up nicely. At high tide, seawater would enter the lagoon but the area was sheltered from the waves and not too deep. A great place for us kids to splash in the ocean and search for sea creatures.

However, due to littoral drift and accretion the beach has changed significantly. The tidal lagoon is now gone; filled in with accreted material. New land has been created. How did this happen?

Littoral drift or longshore drift refers to the transport of sediment, usually sand, along the foreshore due to the action of breaking waves and longshore current. In other words, it is the movement of sand and sediment along the coastline from one place to another. 

A spit is a deposition bar that forms where the direction of the shore changes direction, so the littoral current dissipates. The west part of the San Pareil neighbourhood, including the area west of the posted coordinates, is located on a spit. Note the similarity of the diagram below to the geography of this area. This spit is continuing to grow, and the area northwest of the posted coordinates is the place where it is most noticeable.

Accretion refers to the deposition of sediment, usually sand, which is evidenced by the seaward advance of a shoreline. Accretion causes the beach to become wider, and is the opposite of erosion. 

For accretion to occur (and for this spit to grow larger) there must be a source of material or a “positive sediment supply”. At this spot, there are two sources of material:

 Although you can’t see the river from this spot, you are standing on an area that is part of the Englishman River delta. The mouth of the river’s main channel, which is to the west of this spot, provides a constant supply of sediment flow into the ocean. Over time, increased logging upstream has led to greater volumes of material reaching the coastal zone (Holden: 1989). Sediment from the Englishman River is deposited in the area known as the Englishman River fan (Beuchert et. al: 2009), which to the west of this location.

To the east of this spot are the sandy shallow beaches of Rathtrevor Park and Craig Bay. The prevailing winds in the Parksville area are from the east and southeast, meaning that the “dominant wave direction and resulting net littoral drift is toward the west and northwest” (Beuchert et al, 2009).

Sand from Rathtrevor Beach and Craig Bay moves west along this stretch of coastline until it reaches the Englishman River fan. Here, the material being transported by littoral drift meets material being deposited by the Englishman River. The result is of these two sources is a
growing spit- which involves a frequently-changing landscape and the creation of new, accreted land.

If you look down the beach to the east, you can see areas where the beach has eroded. Several of the properties next to Rathtrevor Park have installed retaining walls and rip rap to prevent further erosion.

There is also an interesting legal element to this as well. Under the British common law (and under the law of British Columbia) riparian property owners are entitled to the adjacent accreted lands. The accretion must be natural and imperceptible- meaning that is cannot be created by artificial means, such as landfilling, and the accretion "cannot be observed in its actual progress from moment to moment or from hour to hour" (i.e. a landslide). If these conditions are met, the waterfront landowner is the owner of any newly accreted lands. In 2017 a number of properties along this beach were re-surveyed to include their accretion. This information will help you figure out the answer to question number 2 below.

To log this earthcache, you must answer the following questions and upload a photograph:

1. What are the sources of the accreted material at this location?

2. At the Arlette Road Beach Access (where the posted coordinates take you), how much
land do you estimate has accreted since these lots were subdivided in the 1960s? How
can you determine this?

3. From the posted coordinates, which area has seen more accretion? The properties to
the east or the properties to the west?

4. Take a photograph of you or your GPS at or near the posted coordinates. In light of the
2019 changes to GC earthcache guidelines, this is a mandatory requirement to log this
earthcache and logs without photos may be deleted .