From the editor’s desk:
Can’t get to the beach? We’ll bring it to you!
Lesley C. Ewing
Beach nourishment versus sea level rise on Florida’s coasts
James R. Houston
Beach nourishment and sea level rise will dominate future shoreline changes on Florida’s 665 miles of sandy coast. Shoreline changes from 2020-2100 are projected along this entire coast using equilibrium profile theory that accurately predicted shoreline changes on Florida’s east coast from 1970-2017 (Houston 2019). Projections for 2020- 2100 are made assuming past rates of beach nourishment for the 30-yr period from 1988-2017 will continue and sea level will rise according to recent projections of the Intergovernmental Panel on Climate Change (IPCC) that include the latest knowledge on ice melting in Antarctica (IPCC 2019). Using the beach nourishment and sea level rise data, equilibrium profile theory is then used to predict shoreline change from 2020-2100 for each IPCC sea level rise projection. Beach nourishment is shown to produce shoreline advance seaward on average for all IPCC scenarios for both the entire Florida coast and east coast and for all scenarios except the upper confidence level of the worst scenario for the southwest and Panhandle coasts. Some of the 30 counties on these coasts will require a greater rate of nourishment than in the past to offset sea level rise for some or all of the scenarios, whereas some will offset sea level rise for all scenarios with lower nourishment rates than in the past. The annual beach nourishment volume for which a county has a shortfall or surplus in offsetting sea level rise for each IPCC scenario can be calculated with the information provided and examples are presented. The approach can be used on coasts outside Florida if beach nourishment and sea level rise are expected to dominate future shoreline change.
Groins, sand retention, and the future of Southern California’s beaches
Gary Griggs, Kiki Patsch, Charles Lester, and Ryan Anderson
Beaches form a significant component of the economy, history, and culture of southern California. Yet both the construction of dams and debris basins in coastal watersheds and the armoring of eroding coastal cliffs and bluffs have reduced sand supply. Ultimately, most of this beach sand is permanently lost to the submarine canyons that intercept littoral drift moving along this intensively used shoreline. Each decade the volume of lost sand is enough to build a beach 100 feet wide, 10 feet deep and 20 miles long, or a continuous beach extending from Newport Bay to San Clemente. Sea-level rise will negatively impact the beaches of southern California further, specifically those with back beach barriers such as seawalls, revetments, homes, businesses, highways, or railroads.
Over 75% of the beaches in southern California are retained by structures, whether natural or artificial, and groin fields built decades ago have been important for local beach growth and stabilization efforts. While groins have been generally discouraged in recent decades in California, and there are important engineering and environmental considerations involved prior to any groin construction, the potential benefits are quite large for the intensively used beaches and growing population of southern California, particularly in light of predicted sea-level rise and public beach loss. All things considered, in many areas groins or groin fields may well meet the objectives of the California Coastal Act, which governs coastal land-use decisions. There are a number of shoreline areas in southern California where sand is in short supply, beaches are narrow, beach usage is high, and where sand retention structures could be used to widen or stabilize local beaches before sand is funneled offshore by submarine canyons intercepting littoral drift. Stabilizing and widening the beaches would add valuable recreational area, support beach ecology, provide a buffer for back beach infrastructure or development, and slow the impacts of a rising sea level
New 2019 sea level projections by the Intergovernmental Panel on Climate Change
James R. Houston
Enhanced tide model: Improving tidal predictions with integration of wind data
Thomas P. Huff, Rusty A. Feagin, and Jens Figlus
Publicly available tidal predictions for coastlines are predominantly based on astronomical predictions. In shallow water basins, however, water levels can deviate from these predictions by a factor of two or more due to wind-induced fluctuations from non-regional storms. To model and correct these wind-induced tidal deviations, a two-stage empirical model was created: the Enhanced Tidal Model (ETM). For any given NOAA tide gauge location, this model first measured the wind-induced deviation based on a compiled dataset, and then adjusted the astronomical predictions into the future to create a 144-hour forecast. The ETM, when incorporating wind data, had only 76% of the error of NOAA astronomical tidal predictions (e.g. if NOAA had 1.0 ft. of error, ETM had only 0.76 ft. error from the observed water level). Certain ETM locations had approximately half (49%) as much prediction error as NOAA. With the improvement in tidal accuracy prediction, the ETM has the ability to significantly aid in navigation along with coastal flood prediction. We envision the ETM as a resource for industry and the public to make informed decisions that impact their livelihood.
Logistical and technical considerations for the use of unmanned aircraft systems in coastal habitat monitoring: A case study in high-resolution subaquatic vegetation assessment
Zachary Olsen, Faye Grubbs, Michael J. Starek, Emma Clarkson, and Jacob Berryhill
In recent years, the technology and regulation surrounding the use of unmanned aircraft systems (UASs) has rapidly advanced. This has resulted in the availability of such technology for more common applications. Here we compare manned versus UAS platforms for acquiring high-resolution imagery of subaquatic habitat for the purpose of boat propeller scar delineation in seagrass meadows in Redfish Bay, Texas. We acquired aerial seagrass imagery in three 20-hectare plots using two UASs and one manned aircraft platform. The three plots represented a priori designations of low, moderate, and high seagrass scarring intensity. Overall, we observed that a smaller amount of scarring was detected in the manned aircraft imagery compared to that collected by the two UAS platforms, and that this disparity was much greater for the high scarring intensity plot. The observed differences in scar feature delineations were at least partially related to logistical difference between these two platforms — specifically, the lower altitude flown by the UASs results in a higher spatial resolution of the imagery that is less dependent on the camera specifications. From a logistical standpoint, the potential gain in spatial resolution via lower altitude flight could result in a reduced pricetag for high-resolution mapped products. Further, the rapid deployment and local operation typically resulting from the accessibility of UAS training greatly simplify the logistics of planning imagery acquisition at the appropriate scale. However, we realize that the current trade-off with regard to higher altitude is the ability to cover large areas with fewer transects and shorter flight time. Coverage limitations for UASs is currently rooted in both technological and legal issues. However, as technology and regulations evolve, the technical and logistical comparison of imagery products from UAS and manned platforms will become increasingly important to natural resource managers and researchers looking to make this transition to UAS.
An ASBPA White Paper:
Local funding for coastal projects: An overview of practices, policies, and considerations
Derek Brockbank, Annie Mercer, Peter Ravella, Tyler Buckingham, Shannon Cunniff, Ken Willson, Gregory Rudolph, Kate Gooderham, Brian Brennan, and Marc Beyeler
The 2019 ASBPA photo contest
ASBPA’s 13th annual photography contest