Natural Disasters

Tidal Impacts and Coastal Beach Erosion

The ocean’s changing tides greatly impact local environments. Potentially hazardous tidal impacts include beach erosion, coastal flooding, and river flooding. The Oregon Coast experiences tidal impacts regularly during king tides season and other extreme tidal activity. King Tides is the term used to refer to the highest tides of the year, typically active in late fall through the winter. Locally, the tidal impacts from king tides have disrupted the bulkhead at the Port of Siuslaw, as you can see in the image below.

Figure 1 – Bulk Head Failure due to King Tides at the Port of Siuslaw 

Check out these resources to learn more about the king tides phenomenon and its impacts:

However, not all tidal impacts are hazardous; the term simply refers to any impact to environments or ecosystems caused by changing tides. Another consistent tidal impact that we experience in the Florence area is the littoral drift, which is the process by which sediment, primarily sand, gets swept up and redeposited in a different location along the coast line. The littoral drift is responsible for the existence of the Oregon Sand Dunes and helps create their ever-changing topography!

Figure 3 – Oregon Dunes National Recreation Area at Woahink Lake

Figure 2 – King Tides at Coquille Point, taken by Rick Poecker 2020 https://www.flickr.com/photos/orkingtide/albums/72157719959771011/

Coastal erosion, one of the most common tidal impacts, is the ongoing natural process of beaches, sand spits, and bluffs being eroded by coastal factors such as ocean waves, currents, storm surges, rain runoff, and strong winds[1]. Coastal erosion is an inevitable part of living near the ocean, but it becomes hazardous when it begins to encroach on human development. King tides and El Nino/La Nina conditions greatly impact the rate and pattern of coastal erosion along the Oregon Coast. Rising sea-levels have exacerbated the effects of coastal erosion.

Preparing for Tidal Impacts and Coastal Erosion

There are steps you can take to prepare your property if you are living or working in an area susceptible to beach erosion or tidal impacts, but be sure to check with the Oregon Parks and Recreation Department (OPRD) about local policies and permitting requirements before taking any mitigation action. Statewide Planning Goal 18 permits shoreline armoring (installing shoreline protective structures) only where development existed prior to 1977[2]. This is to deter from further beachfront development, which often exacerbates coastal erosion and puts residents at risk of loss of property. You can learn more about relevant policies and beach erosion control permitting in the Department of Land Conservation and Development’s “Guidebook on Erosion Control Practices of the Oregon Coast”.

Here are some options for mitigating tidal impacts and coastal erosion:

    • Shoreline Armoring
        • Building shoreline protective structures or beachfront protective structures (BPS), defined as “A static structure that is intended to remain in a fixed position with the purpose of redirecting wave energy and to minimize or eliminate coastal erosion risk to development. BPS are purposefully constructed and intended to maintain that form over time. This includes, but is not limited to, rip-rap revetments, seawalls, groins, breakwaters, jetties, bulkheads, geotextile sandbags, sand burritos, gabions, and concrete or mortar reinforcement such as shotcrete.”
        • Shoreline protective structures are expensive to install and require a permit and approval from local land-use planners and OPRD.
        • Again, you cannot build beachfront protective structures in areas developed after January 1, 1977.
    • Dynamic revetment, aka “cobble berms” or “rubble beaches”
        • A non-structural mitigation effort that involves covering the beach area in front of the property with cobble or gravel.
        • The cobble/gravel slows the process of erosion by reducing wave energy, working with nature rather than against it[3].
        • Dynamic revetment can be costly and requires regular maintenance to maintain “the volume and placement of the cobbles at an effective level”.
    • Vegetation and natural landscaping
        • Planting trees or grasses, or utilizing dunes or other natural features to stabilize the shoreline.
        • This is a popular option, but is limited in its effectiveness. Due to the intense winds and waves along the Oregon Coast, cultivating this vegetation is challenging. Vegetation and natural landscaping are most viable for shoreline areas with lower wave energy.
    • Structural adaptations to your property
        • Raising your house or business on pilings to prevent flooding due to coastal erosion.
        • Structural adaptations are costly, and require approval from your local land-use planners.
    • Managed Retreat
        • The process of physically moving houses further inland as coastal erosion continues.
        • Another costly option that requires extensive permitting and approval from local planning officials.
beach erosion at heceta head

Figure 4 – Cape Creek Bridge from Heceta Head Lighthouse

beach erosion in lincoln city

Figure 5 – 2021 Seawall Collapse in Lincoln, Photo by Casey Felton, New-Times in Newport, Oregon

Always check in with your local land-use planning officials as well as the Oregon Parks and Recreation Department before beginning any sort of coastal-erosion mitigation effort. You can view OPRD’s Ocean Shore Permit Application and Instructions here.

Oregon SeaGrant has put together a flow chart to help guide people towards the appropriate mitigation efforts based on existing policies. You can view the flowchart here.

Want to see where shoreline armoring is being utilized? Use the Coastal Atlas Ocean Shores map to view existing BPSs and BPS eligibility along the Oregon Coast.

You can report coastal erosion conditions to the Oregon Hazards Reporter.

More information about tidal impacts, coastal erosion, and mitigation efforts.

Footnotes

[1]  Coastal Erosion, Oregon Coastal Atlas.

https://www.coastalatlas.net/index.php/learn/topics/14-coastalerosion

[2][3] Guidebook on Erosion Control Practices of the Oregon Coast, Oregon Department of Land Conservation and Development.

https://www.oregon.gov/lcd/Publications/guidebook_erosion_control_practices.pdf?utm_medium=email&utm_source=govdelivery