1. Monitoring Shoreline Change at Port Hueneme Beach
ESRM Program
By: Patrick Costa
Web:
Introduction:
Net longshore currents moved sand southward down the coast for millennia until the 1940 creation of Port of Hueneme (Ventura County) to export farming goods from the productive Oxnard Plain. Sand builds up north of the harbor and is dredged to Port Hueneme Beach. The City of Port Hueneme completed its most recent nourishment of Port Hueneme Beach in January of 2015, allowing me to document beach response to such nourishment and better understand the local processes impacting beach persistence and ecology.
Transect 1: Beach profile shows an unstable scarp face retreating until all beach is gone by April.
Why do we care?
- Public beach access, coastline aesthetics (economic value)
- Lagoons, estuaries, marine life (habitat)
- Water quality, surfing conditions
- Sand supply to other beaches part of the littoral cell
Hypothesis: How quickly does the nourished sand at Port Hueneme return to an equilibrium beach width? Does nourishment have an effect on sand dwelling infauna?
Fig. 1:
completion of nourishment
Winter Storms
Constructive
Summer Waves
Fig. 1:
Net Average Shoreline loss = m/day
completion of nourishment
Winter Storms
Constructive
Summer Waves
Winter Storms
Transect 2: After Transect 1 vanished, Transect 2’s width begins to shrink as the sand depletes.
Fig. 1: Following the Jan nourishment, winter beach width increased along all transects except Transect 1 (which decreased). Transect 1 also steepened during winter in both years due to the stronger wave action. I observed strong seasonality with sand accreting along Transects 2, 3, 4, 5 from constructive summer waves in 2015, and width and slope decreasing along all Transects this winter (Dec 2015-Feb 2016).
Methods:
I continued monitoring initiated by Greene (2015) and Schmidt (2015) between September 2014 and March 2015, sampling beaches from Summer 2015 to Spring I monitored the beach via:
- Beach Width: GPS unit tracking along waters edge at low tide
- Functional Beach Area: Compared beach extent photos at different times/locations.
- Shape & Slope of the Beach Face
Perpendicular to shoreline
5 Transects running from back beach to ocean (perpendicular to shoreline)
Elevation taken along transect using an automatic level
- Diversity & Abundance of Sand-Dwelling Animals
Sand cored every 2m along each of 5 oceanward transects
5 bio transects in 50m sample area
Each 50m sample area is taken at each Transect
Using a clam gun, cored samples collect are sieved and
rinsed using a 1mm mesh screen in the surfzone
Invertebrates are analyzed for diversity and abundance.
Transect 5: Shows a stable back beach prior to nourishment. Over the time sampled, the beach remained stable likely due to the distance from nourished site.
Mean heterogeneity (H’) increases During Nourishment. 1Yr from During Nourish is significantly different, meaning higher H’ when it should not. In contrast, Post Nourish is significantly different from 1Yr Post Nourish, meaning more natural levels of H’ during this time of the year should be higher. The shift in H’ could affect food availability to the snowy plover. *
October 2015
Surveying Methods *
January 2016
Results/Conclusion
- Equilibrium beach width returns at 0.68m/day
- Infaunal heterogeneity increases from dredged sediment
- Beach width loss is significantly quicker during winter months
- Unstable beach face at Transect 1 shows significant erosion
- Transect 2 shows signs of sediment transportation and beach destabilization after Transect 1 vanished resulting in beach width loss
- Transect 5 shows signs of sediment transport and is relatively stable, likely due to being the most distant transect from
nourishment site
Acknowledgements/References:
Alex Greene, Colton Schmidt, Tevin Schmitt, Drs. Sean Anderson, Linda O’Hirok, Kiki Patsch, Clare Steele and Don Rodriguez. ESRM Dept. CSUCI

2. Calculated Change in Volume from Shoreline Tracks
Dredged Sand Placed on the Beach = 1,720,248 m³ (2.25 million yd³) (Brown 2014)
Average Littoral Drift = 948,000 m³ (Herron 2011)
Total Beach Area *Total Area from “Date Line” through Backbeach to total beach perimeter - 09/27/14 Pre Nourish Area (red) = 41,000 m² - 01/21/15 Post Nourish Area (yellow) = 299,000 m² - 10/28/16 Beach Area (green) = 146,000 m² - 01/09/16 Beach Area (blue) = 124,000 m² - 04/16/16 Beach Area (purple) = 111,000 m²
Calculated Change in Volume from Shoreline Tracks
Jan – Oct. =1,281,000 m³/year
Oct – April 2016 = 499,000 m³/year
Jan – April 2016 = 890,000 m³/year
Calculated Volume from Change from Profiles
Oct – April 2016 = 697,000 m³/year
Chart 1 Each Transect date and area (found using the trapezoidal function) are displayed. The last column shows the averages for each of the dates. Dates of interest are October 2015, which has an average 261 m² along the beach at this time. Also, April 2016 has an average of 137 m² along the beach at this time.
Figure 9: Wave Rose shows wave energy in three different time period: (1.) January 2015 to October (2.) October 2015 to April (3.) January 2015 to April (total). In time period (1), wave direction is primarily from the west (270° W) but good amount of southern swell from 247° – 180° S also visits the beach. For time period (2), there are stronger western swell coming from 270° W. There are also fewer and smaller southern swells. Time period (3), is the total of both of the previous time periods (Jan to April 2016). See here are the totals of scattered southern swells with strong west swells. 2. 3. 1.
Completion of nourishment
Graph 1: Beach width vs. time. This graph shows the beach width (backbeach to ocean) over time. Second Y-axis shows beach volume (m³). Peak volume and beach width is shown after the completion of nourishment. Transect 1 shows steady seasonal decrease in beach width. Other Transects show seasonal beach growth. All Transects reduce in beach width in the later months of this study.
Chart 2: This shows the average grain size in microns (mm) for each time segment. Darker shades of color show where the majority of gain size is (<93%). There slight fluctuation in March 2015 with larger grain size.