GUIDELINES FOR ESTABLISHING COASTAL SURVEY BASE LINES 



by 

 J. U-tchaet Hemsley 



I. INTRODUCTION 



"In the past there has been a lack of uniformity In the data 

 secured and In the methods of making studies at beaches before 

 designs for protective works were prepared" (Beach Erosion 

 Board, 1938). 



This quote Is the opening sentence of the Beach Erosion Board's (BEB) 

 "Manual of Procedure In Beach Erosion Studies," written In 1938 (U.S. Army, 

 Corps of Engineers, Beach Erosion Board, 1939). Unfortunately, llttlo has 

 changed since that report was written. Data are still being taken on some pro- 

 file lines that are Inadequately documented or have poorly established survey 

 monuments. Thus, profile lines are difficult to reestablish or relate to other 

 lines established in the study area, and subsequent calculations suffer from 

 the resulting uncertainties. 



Because the beach is a dynamic environment, survey monuments are typically 

 short lived. Use of a properly referenced base line will ensure the recovery 

 of profile lines for repetitive surveys during a study, as well as for subse- 

 quent studies. This report reviews the techniques for establishing a survey 

 base line and discusses the monumentlng, referencing, and documenting of base 

 lines and profile lines. For consistency, the term profile line throughout 

 this report means a line, generally perpendicular to the beach, along which the 

 profile of the beach and foreshore is measured. Profile line is used in lieu 

 of transect, range, and similar terms. For simplicity, the term base line 

 means a control line, generally parallel to the shore, used to accurately lo- 

 cate a series of profile lines. The techniques discussed in this report can 

 also be applied to situations where widely spaced profile lines are located 

 by monumented control points not on a base line. 



Beach profiles are obtained to determine changes in the shape of the beach 

 through time. It is important that the profile lines be accurately located, 

 both horizontally and vertically, so that the profile data can be reliably 

 used. For example, small errors in the relocation of a profile line and, there- 

 fore, in the beach profile can cause substantial errors in the volume changes 

 calculated between surveys of the profile line. The haphazard location of pro- 

 file lines can jeopardize the reliability of the data. Surveys are expensive 

 so it is Important to ensure the accuracy of the data. One benefit of properly 

 establishing a base line is that the likelihood of reoccupying the profile lines 

 in the future is increased, making the data more valuable since they can be 

 readily compared to profile data obtained in subsequent studies. 



II. ESTABLISHING A BASE LINE 



1 . Locating the Base Line . 



Once the study area has been selected, the duration of the study determined, 

 and the profile lines tentatively located, it is time to locate the base line. 

 Whether an actual base line or a series of control points is used, it is good 



