Development of a GIS-based Beach Analysis

Development of a GIS-based Beach Analysis

and Management System (BAMS)

Edsel B. Daniel, Ph.D.

GIS Overview

Geographic Information Systems (GIS) are computer based systems for storing, manipulating, analyzing and displaying digital data related to positions on the Earth's surface. The typical GIS is used to handle various forms of digital maps, which may represent several different layers. Each layer holds data about a particular kind of feature. Some common features are streets, rivers, buildings, vegetation, railway, and coastline. See Figure 1.

Figure 1. GIS Layers (www.esri.com)

Under the Post-Georges Disaster Mitigation Project PGDM, GIS layers (1:25,000 scale) were created for both St. Kitts and Nevis. Currently, additional GIS layers are generated from aerial photos (1:2,500 scale) for St. Kitts and satellite images (provided by the Caribbean Planning for Climate Change (CPACC) Project) for Nevis. These GIS layers are becoming an integral part of the day-to-day planning and mapping operations at the Planning Units in St. Kitts and Nevis.

GIS… More than a mapping tool

A common misconception about GIS is that its main functions are data and map creation. Even though GIS does offer this essential functionality, there are other features such as system integration and application development, which are often under utilized. These features are expected to become more important as end users are demanding user friendly and customized applications that address specific problem areas.

These applications often require the integration of common desktop applications (e.g., MS Word, MS Excel, Adobe Acrobat) and databases stored in various formats. Most GIS packages will not meet every user’s need but they do offer a customizable environment for developing such applications. The development of a prototype GIS-based Beach Analysis and Management System (BAMS) is part of an effort to tap into and utilize these GIS customization resources to build better decision support systems. Click here to see BAMS user interface.

BAMS…What does it offer?

BAMS is a GIS based decision support system developed as part of a research effort to:

a. Improve the tool available for analyzing beach profile data collected under the UNESCO-COSALC Beach Monitoring Program and

b. Expand the results of a coastal erosion hazard assessment that was completed as part of the Post Georges Disaster Mitigation Project for St. Kitts and Nevis.

It was designed for planners and coastal managers to manage coastal resources and beach erosion hazards. The customized tools described in the following sections were based on user requirements identified during interviews held with staff from the PPD, Fisheries Unit and Department of Environment. The Southeast Peninsula was chosen as a case study area for developing and demonstrating system tools and functionality.

BAMS was developed with ESRI’s ArcView 3.2 and ArcIMS 4.0 (Internet) GIS software, and consists of three main application components: Beach Analysis; Predict Episodic Beach Changes; and Setback Analysis.

Beach analysis tools focus on displaying coastal data layers (e.g., coastline, reefs, contours, bathymetry, dunes, COSALC monitoring reference site), analyzing beach erosion data and disseminating this information on a stand-alone system and via the Internet. Options are available to integrate beach profile data and linking it with the corresponding COSALC reference sites. Routines are available to calculate long-term beach change rates and sand volume changes for individual beaches. This allows the user to investigate various trends between different time periods, as well as identify erosion-sensitive beaches.

System flexibility is demonstrated through the ability to integrate and analyze data from various sources and formats, including COSALC beach profiles, sediment rates, and marine debris. Internet GIS tools are also used to expand system functionality so that other stakeholders (e.g. public, NGOs) can access basic beach erosion hazard information via the Internet.

Predicting episodic beach changes tools focus on predicting beach erosion during extreme storm events and calculating erosion damage probabilities. Limited data prevented the use of more advanced modelling techniques such as numerical models. However, available data supported two models: geometric model (GM) and extreme value distribution (EVD). The GM model uses the beach profile characteristics, extreme probability values for storm surge and significant wave height to predict beach changes. The EVD model predicts beach erosion based on statistical/probabilistic analysis of the annual maximum beach width changes (extracted from COSALC beach profile data).

These erosion prediction tools can be used by coastal managers to better analyze and understand coastal erosion hazards. For example, the EVD model can assist with assessing erosion damage exposure and probabilities for existing and proposed facilities on individual beaches.

Setback analysis tools focus on routines and tools for calculating and evaluating individual beach setback distances. Within BAMS, variations in storm-induced beach erosion and long-term erosion due to sea level rise are explicitly considered when calculating setbacks. EVD or GM model is used to estimate the storm-induced beach erosion. Planners would be able to design individual beach setbacks in accordance with the Planning and Infrastructure Guidelines and Standards. This method is an improvement of the existing method of a minimum setback for all beaches. Additional tools are available to evaluate cost components for different setback scenarios.

What next?

The ultimate goal is to implement BAMS in islands that collect beach profile data under the UNESCO-COSALC program. Coastal managers and planners would be able to use BAMS as a decision support tool for coastal management strategies. For example, BAMS could be used to guide solutions to typical coastal management questions such as:

· What have been the erosion/accretion (meters per year) trends and beach sand volume change patterns (cubic meters per year) over a specific time period for a particular beach?

· Where are the beaches that have displayed an erosion rate pattern above a threshold level during a specific period? How many tropical systems passed during that period?

This information would be useful in determining:

· A rotational beach sand mining program where certain beaches can be mined during periods when beach volume is expected to increase.

· Sediment sources and sinks.

· Criteria for prioritizing beach restoration activities or monitoring.

To increase the use of BAMS, seminars/meetings are organized with potential users and other interest groups. These activities are designed to:

· Confirm that user requirements are met.

· Obtain feedback on BAMS.

· Identify priorities for future research and coordination with other research efforts at the local and regional level, namely CPACC.

· Use BAMS to sensitize stakeholders on Integrated Coastal Zone Management (ICZM) and related issues.

To date, seminars and meetings have been held with:

· Staff from Department of Environment and PPD, St. Kitts.

· Staff from the Planning Unit and other Government Departments, Nevis.

· Staff at the Fisheries Unit, St. Kitts.

· Dr. Gillian Cambers, UNESCO-COSALC Coordinator, University of Puerto Rico.

· Dr. Robin Davidson-Arnott, Professor, Geography Department, Guelph University.

· Mr. Alan Mills, GIS Officer, Planning Authority, British Virgin Islands.

The feedback received was positive with an overall indication that user requirements are being met. Dr. Cambers and Mr. Mills also provided useful suggestions on how to modify BAMS for other Islands. Future collaborative work on improving beach monitoring methods will be explored with Dr. Davidson-Arnott.

Additional technology transfer activities planned include:

a) Creation and dissemination of BAMS user manual.

b) Publish BAMS results in coastal management journals.

c) Test/evaluate BAMS prototype with potential users in the Department of Environment, Fisheries Unit and PPD.

d) Assist the UNESCO-COSALC program with investigating the implementation of BAMS in other islands, and improving data collection methods.

e) Investigate the possibility of integrating BAMS with other systems such as CPACC’s Coastal Resource Information System.

f) Investigate more advanced and robust erosion modelling techniques.

g) Migrate BAMS from ArcView 3.2 to the new ArcView 8.2 version.

Closing Remarks

BAMS provides an excellent start for utilizing existing coastal data and GIS technology to develop and implement decision support systems within an ICZM framework. With continued effort at BAMS dissemination, coastal managers and planners can become aware of these capabilities and apply them in their day-to-day activities.