IIAB/Overview

Assessing the Impact of Federal Navigation Projects on Adjacent Beaches:
Methods to Conduct Section 111 Studies

by Julie D. Rosati

PURPOSE: This Wiki-Technical Note presents an overview of the Section 111 Authority, presents methods that can be applied in Section 111 studies, and provides a reference list to previous Section 111 studies. The Wiki-TN concludes with recommendations for a systematic, defensible Section 111 analysis.

CITATION:

 Rosati, J.D., 2011, Assessing the Impact of Federal Navigation Projects on Adjacent Beaches:  
  Methods to Conduct Section 111 Studies, Wiki-TN, Vicksburg, MS: U.S. Army Engineer Research and Development Center.

INTRODUCTION: Section 111 of the 1968 Rivers and Harbors Act, Public Law 90-483 gives the Federal government the authority to study, plan, and prevent or mitigate damages to shores caused by navigation projects. Since the 1970s, there have been numerous Section 111 studies that have estimated the erosion caused by navigation channels, jetties, and dredging and placement activities over the lifetime of an individual navigation project. The goal of a Section 111 study is to evaluate data and conduct analyses such that a determination can be made for the percentage of damages caused by the Federal navigation project. Cost of the mitigation project, usually in the form of beach restoration, will then be shared with the local partner at the same percentage as the original navigation project. Section 111 studies have applied a range of methods, including an assessment of processes (waves, currents, sediment transport) with and without the project, analysis of historical shoreline position and beach profile data, and formulation of sediment budgets. The goal of this document is to provide an orientation to Section 111 studies and present guidance for assessment.

IMPROVED VERSUS NATURAL INLET SYSTEMS: Improved inlets may include dredged navigation channels and placement sites; and stabilizing structures such as jetties, spurs, groins, and revetments. The improved inlet system may differ from the pre-project system in terms of hydrodynamics such as the tidal range in the estuary/bay, circulation and water quality, flooding characteristics in the back bay, and wave breaking characteristics in the nearshore, which are of particular interest to the surfing community. However, the specific intent of the Section 111 analysis is to mitigate for damages to shores -- erosion or other damages -- caused by the federal project. Changes in environmental conditions fall outside the perview of the Section 111 authority.[examples].

The Section 111 study must assess the region affected by the federal navigation channel, including the alongshore extent of influence, and then determine the total damages (Et; presumed to be erosion) within this region. Background erosion (Eb) caused by regional processes, sea level change during the study period, or other non-project phenomena must also be calculated and subtracted from the total erosion quantity. Background erosion rates can be estimated from pre-project data, idealized numerical modeling, and ascillary data. Then the erosion that can be assigned to the navigation project, En, is En=Et-Eb and the percentage of the total erosion, P, that can be supported under the Section 111 authority is P = 100 x En/Et.

TYPES OF DATA FOR ANALYSIS: Ideally, data to quantify the pre-project and post-project conditions would be available and compared to assess the differences prior to and after project construction. Many times the temporal availability and quality of such data are insufficient. An evaluation of background (non-project) processes, such as relative sea level change and long-term regional erosion or accretion, must be accounted for in the analysis. Uncertainty and error associated with each data set must be quantified so that the percentage of damage to the adjacent shores caused by the navigation project can be characterized relative to the reliability of the data and analysis methods.

There are three types of data that can be applied, data characterizing the condition of the beaches adjacent to the inlet, process data, and anthropogenic activities such as dredging and placement:

Condition data in vicinity of inlet

• Shoreline position
• Beach profiles
• Topography and bathymetry
• Sediment type and distribution

Processes

• Long-term sea level change
• Offshore (and nearshore, if available) wave and wind climatology
• Tidal data

Anthropogenic Activities

• Dredging and placement history
• Construction of jetties, seawalls, groins, and other structures
• Mining activities

REFERENCES: U.S. Army Corps of Engineers. 1970. Section 111 reconnaissance report, Bakers Haulover Inlet: Dade County, Florida. Jacksonville, FL: U.S. Army Engineer District, Jacksonville.

U.S. Army Corps of Engineers. 1970. Section 111 reconnaissance report, Johns Pass, Pinellas County, Florida, Report No. 14. Jacksonville, FL: U.S. Army Engineer District, Jacksonville.

U.S. Army Corps of Engineers. 1971. Section 111 reconnaissance report, Fort Pierce Harbor, St. Lucie County, Florida, Report No.14. Jacksonville, FL: U.S. Army Engineer District, Jacksonville.

U.S. Army Corps of Engineers. 1974. Section 111 reconnaissance report, Palm Beach Harbor, Palm Beach County, Florida. Department of the Army, Jacksonville District, Corps of Engineers Report No.18. Jacksonville, FL: U.S. Army Engineer District, Jacksonville.

U.S. Army Corps of Engineers. 1979. Detailed project report, Ft. Pierce, Florida. Jacksonville, FL. U.S. Army Engineer District, Florida. (Do Not Have)

U.S. Army Corps of Engineers. 1979. Panama City beaches, Florida: Communication from the Secretary of the Army transmitting a Corps of Engineers report on the Panama City beaches, Florida, in partial response to a resolution of the Senate Committee on public works adopted April 20, 1970, and pursuant to Section 111 of Public Law 90-483. Washington, DC: Department of Defense, Department of the Army, Corps of Engineers. (Do Not Have)

U.S. Army Corps of Engineers. 1979. Panama City beaches, Florida letter from the Secretary of the Army transmitting a letter from the Chief of Engineers Department of the Army, dated July 8, 1978, submitting a report, together with accompanying papers and illustrations, on Panama City beaches, Florida. The report has been prepared in partial response to a resolution by the Committee on Public Works, United States Senate, adopted April 20, 1970. It is also in response to Section 111, adopted April 20, 1970. It is also in response to Section 111 of the River and Harbor Act of 1968 (Public Law 90-483). (Do Not Have)

U.S. Army Corps of Engineers. 1982. Detailed project report, Ft. Pierce Harbor, Florida. Jacksonville, FL: U.S. Army Engineer District, Florida.