Anura Karunamuni, P.E., and Mark E. Leadon, P.E.

An ArcView Application on Coastal Construction Permitting

The Florida Statutes sets limitations on the seaward encroachment of developments on beach front properties when issuing coastal construction permits to reduce storm damage and impacts resulting from long-term shoreline erosion. Encroachment of new construction is restricted to the line of existing construction. Determination of the existing line of construction is generally a difficult and cumbersome task for permitting engineers. In most cases, major developments are not allowed seaward of a 30-year erosion projection from the location of the existing seasonal high water line.

An ArcView application was developed that allows permitting engineers to delineate the line of construction and the 30-year erosion projection and compare the location of the proposed development with these lines.

Introduction

This paper demonstrates how ArcView can be used as a tool to review compliance of coastal construction pursuant to Chapter 161.053, Florida Statutes and Chapter 62B-33, Florida Administrative Code. Approval or denial of a permit application for construction seaward of the Coastal Construction Control Line (CCCL) is based upon review of a number of issues related to structural design adequacy and siting of the proposed structure. The CCCL, an essential element of Florida's coastal management program, provides protection of Florida's beaches and coastal system while ensuring reasonable use of private property. Two important permit review issues that were incorporated in this ArcView application are compliance with the line of construction and the 30-year erosion projection.

The existing line of construction represents the seaward encroachment of the existing structures on a given segment of the shoreline. In some cases, where no definite building line or shoreline exists, determination of the line of construction can be a very complicated issue. In the simplest case, the line of construction for a given parcel is established using the seaward extent of the adjacent buildings.

Historical erosion rate expressed in terms of a number of feet of erosion per year (for example: 2 feet/year) is used to predict the location of the existing waterline in 30 years. Historical erosion rates are based on historical behavior of that segment of the shoreline and coastal dynamics resulting from present and future coastal construction in the area. The significance of the 30-year erosion projection is that no major structures are eligible to receive a permit seaward of the 30-year erosion projection except for shore protection and single family dwellings meeting specific siting requirements as set forth in Subsection 161.053(6), Florida Statutes.

Coastal Construction Permitting

Generally, beach front properties are relatively expensive compared to inland properties. A 100-foot wide, undeveloped beach front lot (measured in the shore-parallel direction) without any improvements could cost as much as a million dollars. Therefore, the owners usually tend to maximize the use of their investments. On the contrary, improperly sited and designed construction can destabilize or destroy the beach/dune system resulting in loss of beaches and dunes, important natural resources. As a consequence, loss of important values for storm protection, recreation and environmental habitat may occur. This is one of the reasons that regulation of these properties is a vital state interest.

Coast of Florida Study

The database used in this exercise was developed as a part of the "Coast of Florida Study" (COFS), an ongoing study which is co-sponsored by the Florida Department of Environmental Protection (FDEP) Bureau of Beaches and Coastal Systems (BB&CS) and the U.S. Army Corps of Engineers (COE), Jacksonville District. A cost sharing agreement between the COE and the FDEP was approved in 1988 for the COFS to initiate a comprehensive study for the entire coast of Florida. The COFS is a multi-phase, multi-year study based on evaluation and database development of the Florida coast in five regions (Figure 1). The first phase of the study, which is identified as Region III in Figure 1, included Palm Beach, Broward and Dade Counties. The Region III study has completed development of an extensive GIS database, established in mostly ArcInfo coverages, including land boundaries and land use information, environmental resources, geotechnical and other coastal physiographic information.

The primary goal of the COFS is to develop a feasibility report recommending shore protection/storm damage reduction projects for the Florida coast and to develop a comprehensive GIS database as one of the end products of the study. A data dictionary developed under this study identifies the database design, details of data layers and the data structure in which data are stored.

Conventional Approach

When reviewing a permit for construction of a major structure (for example: a building), on a beach front property, it is necessary to evaluate the building location relative to the line of construction in the area. The relative location of the existing line of construction of developments is established using the most seaward adjacent buildings sited within the close proximity of the subject parcel. In the past, permitting engineers have used engineering judgment to determine the line of construction by looking at aerial photographs that were developed on a 1 to 1200 scale.

Most of Florida's beaches are continually eroding due to improper management of the coastal system and natural relocation of the offshore shoal system following major storms. About eighty percent of Florida's beach erosion problems are caused by tidal inlets along the coast. Permitting engineers use the historical erosion rates given in county reports to compute and delineate the projected location of the seasonal high water line in 30 years.

Two of the main drawbacks of the conventional approach are the time needed to collect appropriate data (maps, reports, etc.) and the accuracy of hand drawings. Most buildings on aerial maps have shadows. It is very difficult to identify footprints of taller buildings with larger shadows. Permitting engineers use aerial maps to draw the approximate line of construction. Buildings with shadows make it difficult to delineate an accurate line of construction.

GIS Solution

The example used in this application was based on an actual permit project for construction of a single family dwelling and associated minor structures at Highland Beach in Palm Beach County. As a part of the permit application package, the FDEP receives a survey with state plane coordinates and a site plan for the proposed building. The first step of this application development is to digitize the survey and register the digitized data to state plane coordinates using AutoCad software. The next step is to bring this digitized data into ArcView together with other necessary data layers from the database to determine the line of construction and the 30-year erosion projection.

An existing building footprint theme used in this analysis was developed by viewing successive pairs of aerial photographs through a stereoscope. The building footprint theme was expected to provide an accuracy of 3 feet. However, when quality control/quality assurance checks were made using actual certified surveys, it was revealed that some of the building footprints shown on the database are in error by as much as 10 feet. Aerial photographs are being used as a backdrop in this ArcView application. Historical erosion rates in feet per year for various locations as determined by the FDEP staff have been incorporated into and stored in the database. These rates are stored as attributes in the FEDP range monument theme tables. A query of the database is made to find the historical erosion rate in the area. The historical erosion rate is then applied on the subject site to delineate the projected location of the seasonal high water line in 30 years.

Measuring and drawing tools in ArcView are used to establish the 30-year erosion projection on the proposed building site (Figure 3). The existing data layers used in this case include FDEP range monuments and existing building footprints. In addition to reviewing the two issues mentioned above, the engineers processing permits can use other available data layers such as reef-data, historical mean high water lines, CCCL, etc. to prepare the environmental impact analyses of the proposed project.

Concluding Remarks

The GIS solution used to evaluate permit projects has many advantages over the conventional approach. By allowing the user to access the data interactively in the database, time can be saved for the search of data. Analysis of data such as over-laying, drawing, and queries can be done instantly. Hard copies of analyzed data can be plotted. Also, the permitting engineer gets an opportunity to examine other permits issued in the area. This provides the engineer with a knowledge about other authorized developments in the area.

Environmental and engineering professionals working in regulation make many of their decisions based upon the best quality data available to them. Therefore, their decisions are very dependent upon the accuracy and the quality of the data in the database. In this case, the State of Florida is developing an extensive GIS database of coastal information to assist the regulatory professionals. Permit decisions can be challenged if the data used to evaluate the permit project is not accurate. The FDEP has undertaken a meticulous quality control effort before making the collected data available to public and other sources, including sorting and verifying the data for accuracy.

Acknowledgments

The work presented in this paper is a part of the ongoing development of the GIS database at the Bureau of Beaches and Coastal Systems at FDEP. The authors acknowledge the support extended by the Bureau staff.

References

1. Coast of Florida Erosion and Storm Effects Study, Region III, U.S. Army Corps of Engineers, Jacksonville District, May 1995.

2. Chapter 161, Florida Statutes

3. Chapter 62B-33, Florida Administrative Code

4. Using Avenue, Environmental Research Institute, Inc., 1996

Author Information
Anura Karunamuni, P.E.
Bureau of Beaches and Coastal Systems, Florida Department of Environmental Protection
Tallahassee, Florida 32399-3000
Telephone: 904/487-4469 ext. 167
Fax: 904/ 488-5257
email: ajk2594@garnet.fsu.edu

Mark E. Leadon, P.E.
Bureau of Beaches and Coastal Systems, Florida Department of Environmental Protection
Tallahassee, Florida 32399-3000
Telephone: 904/487-4469 ext. 102
Fax: 904/ 488-5257
email:mleadon@mailer.fsu.edu