DATA COLLECTION METHODS FOR SAND 

 INVENTORY-TYPE SURVEYS 



by 

 Dennis A. Prins 



I . INTRODUCTION 



Beaches throughout the United States serve as primary areas of recreation 

 and as protective areas in the natural transition zone between the water and 

 land masses. During recent years. Federal, State, and local governments have 

 been under increasing pressure to maintain and improve these valuable areas. 

 This pressure has largely been caused by the loss of large volumes of beach 

 sand because of erosion. 



One method of maintenance and improvement of eroding beaches has been the 

 placement of sand of suitable grain size, sorting, and composition. However, 

 beach restoration requires large volumes of sand. The sources of suitable 

 sands in sufficient volumes from lagoons, wetlands, and inland sources are be- 

 coming increasingly difficult to obtain due to increased real estate value, 

 environmental and ecological constraints, and the depletion of nearby sources 

 (Williams, 1976). Also, the cost of transporting sand from land sources to 

 project beaches has increased tremendously in the last several years. 



Shallow areas of the Continental Shelf are a potential source of suitable 

 sand for beach- fill projects and of aggregate for construction purposes. In 

 some cases the offshore mining of these sands and gravels has become economi- 

 cally feasible. This report describes the planning requirements and methods 

 presently used in collecting data to locate and delineate areas of suitable 

 sand sources for use in beach-fill projects. 



II. SURVEY TECHNIQUES 



1. Essential Data . 



A minimum of the following three types of data are required: medium- to 

 high-resolution seismic reflection profiles, horizontal position control, and 

 20-foot-long (6.1 meters) sediment cores. The seismic reflection profiles are 

 obtained by generating high-energy acoustic pulses near the water surface, 

 which are reflected from the subbottom interfaces, and recording the acoustic 

 return signal on a continuous paper chart. The compositional and physical 

 properties of the sea floor and subbottom sediments at various depths produce 

 acoustic contrasts which appear as lines on the records (Fig. 1) (Duane and 

 Meisburger, 1969) . 



Horizontal position data are usually obtained using an electronic position- 

 ing system. The position (fix) of the vessel is recorded at frequent intervals 

 (usually every 2 to 4 minutes) and is simultaneously recorded and labeled on 

 the seismic reflection record by an event mark. For this type of operation a 

 positioning system is required with an accuracy of about 10 feet (±3.0 meters). 

 Systems with this accuracy usually operate on the principle of pulse radar and 

 are limited to line of sight. The basic system consists of a master unit 

 mounted aboard the survey vessel and two shore stations. Each navigation fix 



