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A METHOD AND SELECTED APPLICATION FOR USING AERIAL PHOTOS IN DELINEATING HISTORIC PATTERNS OF BEACH ACCRETION AND RETREAT SEP 1979 GB 458.8 .H83 1979 A Method and Selected A pplicati n f ng Aerial Photos in Delineating Historic -Patterns of Beac!@@@tion and Retreat Dennis H Coastal Zone Man ekjt Project Urban and Region nn i@Trograrn so Universi F74' This do prepared for the f Hawaii Departm Plan nd Economic Development y the rb gional Planning Program University of Hawaii The preparation of this report was financed in part through a Coastal Zone Management Program Implementation Grant from the United States Department of Commerce September 1979 TABLE OF CONTENTS INTRODUCTION .................................. .................... I General Problems Addressed .............. ...................... 1 The Use of Aerial Photos in Monitorl Shoreline Changes. 3 METHODOLOGY Determining Scale on a Photo.. 6 ........... Beach Index Lines ............. .......................... 11 Calculating Beach Change ..... @,& . .......................... 12 MEASURING SHORELINE CHANGES: ACCURACY LI IONS ...................... 13 Relief Displacement..:.. ............................. 13 Measurement Errors ... ........................... : .... 16 Tilt ................... o . 16 Error in Computing Photog 16 Summary of Error Analysis.. .............................. .... 18 DISCUSSION ......... ................................ 22 RESULTS ........ ............................................ 28 CONCLUSION- .. ............ o....... o ......................... 33 BIBLIOGR ...... .................... o............. - ............ 34 APPENDIX ........... o............ 0- ........................ 39 4@ A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat Dennis Hwang University of Hawaii INTRODUCTION General Problems Add In Hawaii.' there is no single geomorphic e which is more unstable than the beach zone. Over periods of time rangin y years to a f ew days, the beach may be m arkedly altered in i e, volume and other characteristics. These changes may be ca y nu factors such as storms, seasonal and long term variations in wave. itions, re ctions in the rate of sand production, increases in exposure d ! si@@ ue of protecting headlands or reefs, and human activity. The constantly shifting sands_ have posed some serious problems with regard to coastal zone managern problems are summarized below: Siting of New Beach Structures 1) On some beach built on what were once back beach ar isr ing the potential for beach erosion. Subseq h retreat has resulted in undermining of t ructures. The houses built an Lanikai Beach on are an example of this problem. Obviously pot for beach 'retreat must be co sider tr ures of any kind are built. The ro t o nt problem is determining how far in sh ures must be placed to be safe from na Re ures to Save Present Structures from Beach a e of 'beach retreat relative to now-existing 2) _@ ME! u c t the correci remedial policies are dependent on t h e s. c f the problem. For example, if a well developed beac i many buildings is threatened by erosion, then 0 e works or artificial beach maintenance may be d. However, for a slowly retreating shoreline ning a few old houses, no governmental action may- be -quired. In determining the best management policy, it should be realized that some remedial measures may make it unlikely that the beach will grow back, even if the conditions that led to its retreat are changed. Therefore, it would be useful to know if a particular beach has a historic record of continuous erosioni or cyclic accretion at and retreat. A Method and Selected A pplication for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -2- Regulation of Sand Mining 3) The removal of sand from backbeach areas within the reach of uncommon storm waves or tsunamis should be prohibited because beach retreat may result if sand from the littoral cell is transferred to the removal sitg, In defining the boundaries to which sand mining prohibited, the possibility of beach erosion must ecognized. The problem in this policy area is deter the inland extent of prohibitive sand removal. Acquisition of Land for Public B ar 4) In acquiring beach front and lands for public beach parks. the potential for be r must be considered. For example, if a plot of e ing 100 feet from the shoreline is needed, it w ttle use to acquire just the 100 feet if the shor retreating 10 feet per year especially if the plot ed by private lands subject to future development permanent structures within the next few @1-111P ). Extent-of Private r s i 001@11-5 5) M any of the boundar een public and private portions of the beach are defined by the debris line, vegetation 1* iff sea-level lines. Since beaches are so uns use any of these boundaries means that the private property is constantly changin assess land values for taxation purl: e cessary to periodically resurvey an area. a riate time interval for resurvey would depe tability of the beach in question. In any iv agement problems mentioned, the best effective decisions m on the magnitude of beach instability. Therefore, it is-- extremely tan ave information on beach areas likely to prograde or retreat a I as about the trends, ranges and rates of long term beach change. Al ave been several studies in the past dealing with the beaches of Hawaii,' actually very little information concerning long term beach variations. M o and Chamberlain (1964) describe characteristics of 112 beach sites for the seven major Hawaiian islands. This comprehensive report is the major source of information concerning seasonal beach changes. However, the short period of field work conducted in this study precluded a description of long term beach trends. A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -3- Campbell (1972) provided additional information on beach erosion for 33 selected beach sites. Resurveys were conducted to compare with the data of Moberly and Chamberlain. While- most study sites showed insignificant changes in the volume of beach sand, a few areas did display net accretion or erosion. For Hawaiian beaches, this work provides the most information on the magnitude of long term changes. However, the ten year observation period may have been insuf f icient to define the ranges and trends in past S *ne positions. . The Army Corps of Engineers in 1971 co available information from previous studies to define 54 circum-Hawaila hich are critically eroding. In the report the description of beach chan qualitative and served mainly to identify existing erosion hazard ntitative data can be found in many of the Army Corps of En S indivi case reports on beach erosion. A recent study by the Corps in I ckdes survey data from 1967 to 1970 for Barking Sands.' Hanalei Bay and Kek i; Haleiwa. Kailua and Sunset on Oahu,- Kaanapali on Maui and Papoha kai. In this study surveys were conducted over 6 month intervals at original LM oberly and Chamberlain survey ranges. No study has yet- provided concise info on on the magnitude of long term beach change for more than a f Ir-urvey methods are very accurate in determining short term beac use in monitoring historic shoreline movements repeatedly encou on us problem: a lack of- past surveys through which beach changes . e, pared. Past measurements of the beach may be scarce because the need 01'lzl@them was not recognized at the time. Accurate surveys me ian beaches may exist for only a ten-year span. Extrapolating d 5 of ch change beyond this time interval can be difficult. For exam u e in 1962,: 1963 and 1972 may indicate that a particular beach is ve Does this mean that beach structures with a 30 year life span ea ay e built free from the threat of beach retreat? The Use e raphs, in Monitoring Historic Shoreline Changes On t e survey method, which forms the basis of this report, lies in lizati aerial photographs. By crosstime comparison of aerial photos.' st an sent shoreline positions can be defined and perhaps future change icted. - T of photo comparison to monitor shoreline changes has been successf ully yed for many sections of the United States. In the earliest studies,' descri ns of beach change were mostly qualitative and utilized oblique as well as vertical photographs (Howard, 1939; Dietz. 1947; Shepard, 1950). The emphasis on vertical photographs gradually increased as their versatility allowed qualitative and quantitative. descriptions of coastal morphologic changes (Tanner, 196111 Athearn.' 19630, El Ashry and Wanless. 1965; Cameron. 1965a; Cameron, 1965b; El Ashry and Wanless, 1967; El Ashry and Wanless,@ 1968). A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -4- In t.he last ten years, aerial photographs have been extensively used to collect precise measurements on historic shoreline changes. Moffitt (1969) studied beach erosion in Monterey Bay, California. by orienting reference points and shoreline points on the photo into the State Plane Coordinate System. While this procedure may give accurate results, its use is not required unless the absolute position of the shoreline is needed. Langfelder et. al. (1970) used aerial phot ogr to document beach changes over a 30 year period for the North Carolina co n this study, transects were established every 1,000 feet and distances fr reference points to the shoreline were measured. Beach erosion of the Georgia barrier system w documented over a 30 year period using methods similar to L n r ertel, 1973). Shoreline changes at Sargent Beach, Texas, were reveale 5 of topographic maps and aerial photographs (Seelig and Sorensen, 197 u on beach instability in Pamlico Sound, North Carolinai were based on aerial photographs over a 33 year period (Stirewalt and Ingram, 1974). FIS eegan define procedures for using transects, on photographs for a study of b e ion on Rhode Island (in Tanner. 1978). For the state of Hawaii, an air photo ey on past shoreline movements was conducted for Kailua Beach P Past studies indicate t ri otographs are an excellent tool to document historic shoreline ir use in the coastal zone is especially advantageous for several re ons. eral., imagery of the Hawaiian coastline has been obtained more fr uent he past 30 years than maps, charts on surveys have been ma 0, photographs provide an efficient and economical means of c s ce information can be obtained without the expense of costly sur r Ily. an aerial photograph records an almost infinite amount of opposed to maps and charts which contain selected detail subj h interpretation (Stafford and Langfelder, 1970). The use of ae raphs to collect beach instability data is not without its drawbacks. photograph may record conditions which are not typical of me ons. or example, strong winds may cause unusually high waves giving arrow appearance. This problem is somewhat. alleviated by the f a at p raphs are obtained only on clear days suitable for photograp nother lern is distinguishing on a photograph between long term beach c and term changes due to seasonal fluctuations and storms. Ideally,' to s taken at the same time of the year should be used. Unf ortuna not always possible as the quality, quantity and periods of photo covera or each beach. Problems also exist in the photo resolution as well as erro s inh nt in the image itself. It is clear that these problems must be resolved before the photographs can be effectively used in this study. The methods used to reduce or eliminate these problems and to estimate their magnitude are outlined in later sections of this report. A M ethod and Selected A p .plication for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat 1b -5- METHODOLOGY The first phase of this project was determining the aerial photographs which were available for study. This was an important part of the project because the periods of time coverage and the type of imagery available are sometimes determined by what exists. Photographic inventories were conducted for iles of the R.M. Towill Co., Air Survey Hawaii, Hawad Institute of Geophysi d Army Corps of Engineers. An investigation of potentially useful aerial ph hs Was made for the United States Geological Survey, United States Air ct and Geodetic Survey, National Ocean, Survey,* Bishop Museum, Stat i brary Hawaii. Once the inventory of the available og aphS Was completed, flight lines of a particular beach were ordered for d* e ars. When possible, photographs taken at the same time of the year we le to minimize the affects of short term seasonal changes. In the first prototype study of K flight lines for 1949, 1963, 197L 1975' and 1978 were provided by the ent of Planning and Economic Development. These photogra used ong with a 1957 Army Corps of Engineers flight line. The set ed in scale f rom about 1:2,400 to 1:4.800 and were used to es racies involved in measurements at different scales. An important part of Ithis s ncerned determining the best time interval between photographic fli lines. ously, increasing the number of monitoring flight lines would docu ch ges more accurately. Beaches which have a history of reversing etion or erosion require more continuous monitoring than a W e undergone stable unidirectional change. Unfortunately, the rs' each types and their processes precludes a predetermination e um monitoring interval (Morton: in Tanner, 1978). The optimum m rval would be the point when the value in labor and money equals the v mation obtained from additional flight lines. I , t is og hs 'Were selected at roughly five year time intervals. The x t depended on the imagery available. A f ive. year obser ati riod s allow documentation of significant long term beach changes e red the affects of short term variability due to seasonal change a f aches on Oahu. the observation period will have to be increas ck of photo coverage. After sui image@y was obtained. points along the beach were selected on each photograph. These points, which will be referred to as stable reference points, must satisfy three requirements. First, stable reference points must have a fixed ground position over the beach monitoring period. These points can then serve as a marker by which beach changes can be measured against. Secondly, the A Method -and Selected A pplication for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -6- points selected must be located as close to the beach as possible. Since photographic scales are determined between stable reference points within close proximity of the beach.: the variation of scale within a photograph due to tilt becomes a significantly less important factor. Finally, the stable reference points must have a minimum of ground elevation in order to reduce relief displacement problems. In general, the corners of single level.hous re used as stable reference points. These structures tend to have clear disti undaries which can be easily distinguished on a photograph. After suitable es had been selected,: the points on the photograph were sequentially num Determining SC kPhoto @L<Irequired because of the variable A scale determination for each ph p flying height of an airplane along the I'*,-- The scale of -each photograph is determined by use of the following for Photo Scale = Photo Distance Photo Di X Map Scale Ground Distan Orthophoto maps produ Towill Company were used to determine the photographic sc or, lua Beach. These maps are controlled photo mosaics which have been d for tilt and scale variations along the flight line. Orthophoto maps all y accurate measurements of the ground distance between stable ence. s. An example is given to illustrate this point. It is generally t stric-el limit -in accuracy to which the human eye can consisteAl te in on a photo oi map is .01 inch (Tanner 1978). Since measuring C res locating two points,: an error of up to b2 inch can be expecte y using precise measuring scales and a ten times magnifying glass,' t measuring error is about .005 of--aft-inch-(-T-able #1). This figur e u a working number throughout the remainder of this report. on ophot p@: at a scale of I in. 200 fut a measurement error of .005 of repr a ground distance error of I foot. The. average distance betw n refe points used 1n@this -study is approximately 5 inches on the orth 0 0 feet on the gr 'ound. T 'aking the rneasuring errors into consideratio und distance between the two stable reference points is 1, '000 + I foot. Therefore,' using the orthophoto ---maps as ground control allows a very accurate scale determination f o*r each photograph. Unfortunately,; orthophoto maps -have not been compiled for all sections of the Oahu coastline and for some beachesi the coverage is'partial or non-existent. A M etho'd and Selected A pplication f or Using A erial- Photos in Delineating Historic Patterns of- Beach Accretion and Retreat -7- For beaches with partial orthophoto coverage, ground control can be extended by using the 60% overlap of the photos. In this procedure; a flight line is selected with the least amount of tilt and scale variations. This is determined by comparing the relative positions of selected points on adjacent overlapping photos (Fig. #1). After a suitable flight line is selected, ground control is extended by successive measurements on adjacent photographs (Fig. #2). In this method,: the errors accumulate for each photograph in which cont I en ro t ded. However@ in later sections of this report it is -shown that this proce ields more than acceptable error levels. Table #I-An Evaluation of M_ em Five students measured the dista between well defined points, To prevent biasing,' none of the measurem b "*,en the same,points were made consecutively. All results were conceal students. Student-# Distance Distance #2 #1 2.407 in. 2.405 in. #2 2.412 in. 2.412 in. #3 2.6 2.408 in. 2.68 .2.410 in. #4 in. 2.4,12'in' 2. 7 in. 2.410 in. #5 2.689 in. 2.410 in. 2.688 in. 2.410 in. X 2.687 X 2.410 As 9 that, mean value of the measurements approaches the correct distan ma error between any of the twenty measurements is .005 inch. ative estimate, this value is established as the limit' in measureme cy@ On beach ithobt orthophoto -coverage, the 'only alternative for: ground control would b 'e field measurements. In,this case,t a few. ground distances could be measured and the control extended to all sections of the beach by photographic measurements. This method Nould yield accurate results and reduce the time of field work considerably.. A Method and Selected Applications for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat 4-3 04- S- -C 4- -P 0 w Cn u 0 0 Ln (n -P to 0 a) E Co C-j Qj 4J 4- #10 0 0 4L) E =3 CL E r- 4-) 0) 0 E 4-) 4-) 0 to _I_- 4-) CO Ln =It= cn CL (v _I-_ CL go C7) S- 0 M 4-) 00 4-) -9-- 4-; 0 CL- 0- (v 4-) _I_- m4J 0 -P 0 1 _C; u a) (D (u = +-) @ 4-1 (a a) 0 u En @Iz' I-Ik LL C%J. m 0) Cu (A' to A B C D 3 3 3 5 4 4 4 4 3 5 .2 'A ww Fig. #2-0 On beaches with partial orthophoto coverage, the ground.control can be ween pt. 3 and..pt. 4 is known,-then scales can be de If the distance bet for photos B and C. This will allow the distances between pts. 2 and 3 pts. 4 and 5 to be determined. Scales for photos A and D can then be c A M ethod and Selec" ted A pplication f or Using A erial Photos in Delineating Historic Patterns of Beach Accretion and Retreat _10- Beach Index Lines After the photographic scales have been calculated, the distance between stable reference points and a beach index line is measured for all photographs. There are three index lines on the beach which can be used to represent actual beach location (Fig. #3). Previous aerial photographni studies of beach areas have used the vegetation line,' high water line and watE;* . Each has its advantages -disadvantages. and The vegetation line., marked by the se it of existing perennial vegetation,' is an indicator of the highest annua ox, 19.78). This index line is especially useful because of its. clear on tograph. In addition, the position of the vegetation line would ref ong ter each changes while th; affects of seasonal variations would be mini The use of the vegetation line is no 0 s problems. The position of this line on eroding beaches would chang dily than on accreting beaches. However* a five year monitoring inter flow the vegetation to reach some degree @f equilibrium with an accretin Another problem in using the vegetation line is that human activity or wl n sand may after its position. Generally,'. these modifications on a photograph by 'the highly irregular appearance of the ve e beaches, the vegetation may be located on the top of a berm ay lief displacement problems. In some limited areas,' the vegetation lin exist because of manmade structures or unusual beach features. The high water mark tingu on the photograph as a line separating dry sand from moist sand. I e po n of the high water line is not af fected by tidal f luctuations beca. ords the extent of highest wave runup during high tide. However, 0 s sands, the high water line may not exist (Rib' 1957). If the w in is present: its position is highly variable and dei;ndent on the n tors: 1) the ex@ent of wave runup; 2) atmospheric conditions related ion; 4) the location of the ground water table; 5) the elevation of the re water level (Weber- 1969). Probably the greatest problem in usi ig r mark is distinguis@ing between wet and dry sands on a photogra The t ndex which may be used to document beach change is the water lin a pho ph the position of this line depends on the degree of light penetra he the extent of wave runup, and the tide level at the time of the p beaches which have high tidal ranges and gentle slopes, the Water line rn laced significantly between high. and low, tides. Using the prototype. study of Kallua Beach as an example, the displacement of the water line caused by tidal changes can be calculated. For Oahu, an average of eight different tide stations yields a mean diurnal tide range of about 1.9 feet'(Tide Tables,* U.S. Dept. of Commerce; 1973). The diurnal range is defined as -the 710% Ift M M No M M M M M M M (D (D =r O@q CL (D > High Water Line Vegetation Line 0 0 1--% D M 0 v Zone Grey Ton n Still Water Level D --7 CL 0 77 Fig. 3. Beach Index Lines (Adapted from, Weber, 1970) A Method and Selected Application for Using Aerial Photos-- in Delineating Historic Patterns of Beach Accretion and Retreat -12- elevation difference between mean higher high water and mean lower low water. For some. sections of Kailua Beach,' the slope is approximately 1:15 (Noda,:* 1977). Using these figures,' a displacement of the water line of up to 28.5 feet may result from tidal changes alone. For thi's reason,@ some aerial photographic studies have made tidal corrections when using the water line (Moffitt, 1969). However; the use of any constant tidal correction factor for a beach with varying slopes introduces further inaccuracies (Langfelder et. al., 1968). In tIA: tudy; no tidal corrections were made. Another problem in using the water mar tinguishing the line on a photograph. Poor contrasts exists between nd land'. because the wavelengths of the light spectrum that black r9matic film record are characteristically reflected by land and w eber. For this , study,@ two beach index li r ed. It is believed that the vegetation line provides the most inform c ning long term beach changes. Distinguishing the vegetation line on a 9 is easier and thus more accurate than any of the other two lines. The the water line is also used to collect beach instability data. In order line ef f ectively@ : it is important to know how tidal, fluctuations may affect i on. The position -of the ' water line is also sensitive to long term rt term anges, in the beach profile. This must be fully realized in order t long term changes which are in reality only short term changes. beach where the vegetation line is missing or the water line is unde a gap will be left in the data. alcu a ach Change On each photogra C - between stable reference points and the beach index lines is m d. tographic distance multiplied by the scale of the photograph gives ro, ce between the reference point and the index lines at the time o to y. The change in ground position for beach index lines can then be successive monitoring intervals. The net change in position for each o riod,- divided by the monitoring time interval gives an incremental r C the beach location. The incr of change computed for any observation period assume that the tr nd ra f change were constant, for the beach section under study. If r of assumptions is incorrect,@. then the calculated rates of change wj d to derestimated. For.example,@ Suppose ten feet of beach erosion two photographs over a five year time lapse. Then the incremental the beach position would be -2 ft./year. However,* if the beach accreted the first three years 12 ft. anderoded in the next two years 22 f t.' then the tru rat6s of change are +4.0 ,fi./year for'the first three years and -11 ft./year for the next two years. Thus., the estimated rate of change has been underestimated by assuming the beach underwent constant unidirectional change. A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -13- The five year monitoring interval selected in this study should be sufficiently frequent to determine long term beach trends; to calculate rates of change, and perhaps for predicting future rates of change. However,: the limitations inherent in calculating rates of change from net shoreline movements should be realized (Morton: in Tanner,' 1978). MEASURING SHORELINE CHANGES: ACCURACY ATIONS Whenever data on shoreline changes is prese measurements should be accompanied with a statement on the probable racy. In this report; the magnitude of these limits is estimated e t ferent situations in which ground control may be obtained: orthop o coverage; partial orthophoto coverage@ and field measurem Zh w e computations which follo fikhe prototype study for Kailua. employ the specifications of the photogra e Beach. According to Scherz (1974), th nd ranges of errors in using photogrammetic materials are listed in decre r: 1) Relief Dis lac terrain) 2) M easure en rs ith technique) 3) Paper Shrinkag 0 to .5% 4) Tilt : 0 to .3% 5) Fil 0 to .1 6) L is n 0 to.1% 7) al Plane Flatness 0 to .-01% re ilm Shrinkage 0 to .005% For t udy, th item should be added to the list. The error in determini cale photograph may be an important factor in limiting the accuracy t gy. Of the n rs listed" only relief displacement; tilt,; measurement errors and photog a. hic ale erro@ are Included - 'in the 'accuracy analysis. Paper shrinkage and film shrinkage are not important factors since a scale is determined for each photograph. Lens distortion, differential film shrinkage and lack of focal plane flatness are insignificant when compared to other possible errors.. m P A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -14- Relief Displacement The displacement of an objett on a photograph due to its relief is shown on Fig. A. At sea level there is no relief' so one might think that relief displacement problems are not a factor in measurin@ shoreline changes. However, the position of a beach index line is usually measured relative to tructures having elevations considerably greater than sea level (Tanner, 1978). The magnitude of relief displacement is give e following formula: m = rh M Off itt where m the displacement on the graph o e top relative to the base h height of the object H altitude of the plane r radial distance fro nter to the image of the ground point The value of the parameters used in the fo ing computations are: H 5.'000 ft. (Th the 1949 f light line f or Kai ac r 10 in. (The f the photographs allowed all stable! ence points to be selected in 10 es of the photo center. The f-the otographs are 27 x 27 inches) h 25 ft. the estimated dif f erence in ation between the stable reference nts and the water line) T le ment of the object is then; M (10 inJ (25 ft.) .05 in. 5. 000 ft. The graph* le for the 1949 flight line is approximately I in. 200 feet. T 'in nd distance due to relief displacement on the photo would then.be t is horizontal. displacement may be misinterpreted as beach erosion or acc Relief displacements, on a photograph are'the most serious photogrammetric error in this study. Even by selecting single level buildings and staying as close to the photographic centeras possible,' an error of up to ten feet may still result when measuring distances to the water line. Fortunately,: relief distortion problems are less serious for measurements to the vegetation line. On Kailua Beachi the A Method and Selected -A@pplicatio'ns for' UsingIAerial Photos in Delineating Historic. Patterns of Beach Accretion and Retreat -15- Relief Displacement m r--- r' Ib P, Sec, It-el @,@igr @,.Relief displacement 6n''.-a'@hotograp@,-@t4offitt,1967).- A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -16- elevation 'difference,' parameter h,; is about 15 feet between stable reference points and the vegetation line. This elevation would result in a relief displacement. error of 6 f eet. One additional factor may alleviate the problems of -relief distortion. Any relief displacement on a photograph can be divided * to components parallel and perpendicular to the shoreline. When measuring dis s to a particular part of the beach.: the perpendicular components are the detrimental. On the 1949 photographs for Kailua Beach,' the maximum rn perpendicular to the beach is 9 inches. Substituting 'this value into para ts in a distance error to the vegetation line of 5 feet. The component of relief displacemen Bel. to shoreline is a more serious problem when computing photogra c,! e ,krs. This factor is considered in 0 section #4 of the err r analysis. @@M@ M easure E The distance between any two the photograph can be measured to an accuracy of about .005 of an inch ab On'the 1949 flight line of Kailua' Beach,: at a scale of I in. = 200 ft., this me ment error represents a ground distance error of -I foot. Generally. tilts on a ph of up to 30 may result from weather conditionsi pilot errors.' etc. (Sche 4). Figure #5 shows the geometry of a vertical photograph and gra h a 30 tilt. The ground distance between AB measured from the otog, p is .3% off compared with the correct distance computed fro otograph. For the 1949 fli ne, ailua Beach, the average distance between stable reference points ation line is about one inch. The effect of a .3% tilt error on the compu istance is: -F Orn tilt X .3% .1.00 in. distance N X .003 in At a cale of I in. = 200 f t., the change in ground distance resulting on the photo is .6 feet. Thus,1 photographs with a 30 tilt or less may be us curate measurements of the beach. A f ew of the photographs used in this study, were excessivley tilted. In this case,7 accurate measurements are still possible provided several scale determinations are made perpendicula, r to the beach for each photograph. A Method and Selected Application for Using Aerial Photo5 in Delineating Historic Patterns of Beach Accretion and Retreat -17- Error in Computing Photographic Scales In order to convert photographic distances to ground distances,' an accurate sale determination is needed for each photograph. The scale of a photograph can be found by use of the following formula: Scale = Photo Distance Ground Distance The photo distance measured between an ints may be in error f rom two major sources. The actual measurement 005 inch (Table #I). This would be the only error if afl the points e I ph were at their true ground positions. However. relief displace f stabl derence points relative to the vegetation line ma@ contribute an Mal error of .03 inch (section #1). This value is a maximum estimate for t (a) not all the components of relief displacement is parallel to the Ii nd W the two stable reference points selected for each scale determi located 'sufficiently close so that in all cases the relief - dispiacements r negligable or compensating. The combined effects of both. errors result in m error in the measured photo distance of .035 inch. In the section of this pa nation of Scaleill it was shown that the ground distance could be ure accuracy of I foot from orthophoto maps. The effect of this erro t ale accuracy can be computed using the 194 9 flight line of Kailua Beach ple. Suppose the photo ce red is 5.00 � .035 inches and the ground distance is 1,1000.1 1 f ex ed scale of the. photo. if no errors were involved is. Scale 0 0 x 10-3 in./ft. I in. or f t. 200 ft. I in. = 200 ft., The ef stimated errors on the scale can be computed by. taking partial der* es o cale formula. V .035 3.50 x 10-5 in./ft G 1,:000 fto dS (1.-00 in.) G ft.) 5.0 x 10-6 in./f t. FG (1,:000 ft.),6 Combining the two error values and adding them to the expected scale of the photo results in the following change. (5.00 x 10 .3. in./f t. (4.00 x 10-5 in./ft.) 5oO4O X+ 10-3 in./f t. I in./198 ft. or'I in.'= 198 ft. > aJ/ If:. f= 8.25 in. b) For- a h a 30 ti I t: lotograph wit Z= 5,000 ft. f- 8 5 in. (D Q Z=5,000 @ft. ap= pb = 3.33in. 0 21.9T then; tarf'. (3.33/8.25 21.98 a 18.9e AB=1 2 21.).98 i=5,000 ft.) M =403 A 24.980 orq AN= (5000 ft.) (tan 18.99)=. 1.719.6 ft. (D NB=' (5000 ft.) (tan 24.9T)= 2,329.4,ft. AB= AN NB= 4,049.0 ft. 0.,+ > 0 0 b > 00 0C Oro > Of (D0 A bL Fig. 5. Tilt on a photograph. For the vertical photograph, the computed distance between AB i's 4036.2 feet. - On a photograph with a 3"tilt, this distance is computed as 4,049.0 feet. The error 'is 02.8/4036.0 (100)= ..3%. (Adapted from Scherz,1974) A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -19- The range in scale resulting from the estimated errors is Lin. 200 4- 2 feet. Sifice the distance between stable reference points and the vegetation fine averages I inch on the photo,: the scale error results in a ground distance error of 2 f eet. Summary of Error An ly Table #2 summarizes the estimated er ich may result from using orthophoto maps as ground control for the 1978 flight lines. The procedures used for estimating the errors on aphs were similar to those outlined in this report. The total sum of errors for the li 'lines appear at the bottom of the table. These figures are most likel stimation because any of the errors may be accumulating or compe may range f rom zero to their maximum estimated limits. For this r robable error has been calculated and appears below the total error figure The probable error is estimat by m g three assumptions. -Firsti@ the errors are assumed to follow a al error distribution. This is a reasonable assumption because ve a f inite variance and seem,' to the first approximation, to be m ts. Secondly, it is assumed that the maximum estimated errors are t d deviations away from the mean error values. As a result; about 95% of errors are within the interval defined by plus or minus the maximum estima ror. This is believed to be a conservative estimate. Finally, it is as that errors are uncorrelated or independent of each other. This req sfied for relief displacemen *t. tilt and measurement errors bu raphic scale errors. In this study,: the total probable error is ap a ssuming the photographic scale error is an independent deviatio Based on e assumptions.: the total probable error can be computed to a 95 co nterval by summing the squares of the individual error compone t 69). When comparing beach changes on the 1949 and 1978 f lig limit in accuracy can be computed by the procedures shown at the m 6 #2. In this case, the limit is about 11 feet. S the. s@ or the six f light lines used in this. study varies from 1:2,400 A Cc'uracy in comparing any two of the flight lines also changes.. otype study of Kailua Beack the maximum error in comparing any the data points is about 12 feet. The procedures used in estimating this fig are similar to those outlined. on Table #2. For beaches which have partial orthophoto coveragei the ground control is extended by successive measurements on adjacent overlapping photographs (Fig. #2). In the first test study for Kail 'ua Beack this procedure was used to extend ground control from the middle -portions. of. the beach to both ends. Scales for all J, A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -20- photographs were then determined. Distances between selected points on the photograohs were converted to ground distances and compared with field measurements. This comparison was made only for points at opposite ends of the beach. Since ground control was extended,- the accuracy of measurements at the end portions of the beach would be dependent on those in between. Table #3 shows the results of the accura t. The maximum error is 1.1% for all the measurements made. It is clear extending control by this method can yield very accurate results provided raphs with the least amount of tilt are used. As mentioned previously,- t raphs are selected by comparing the relative positions of common t over apping photos (Fig. #1). For this study of Kailua Bea t. involved in using photographs with extended ground co photographs with orthophoto coverage are assumed to be about equ er e, on photographs with extended ground control.' the maximum error for d beach change is about 12 feet. -z' A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -21- TABLE #2 - Summary of Errors for the 1949 and 1978 F1ight Lines Using Orthophoto Maps The 1978 photographs were taken at a flying height of 6,000 feet with a 6 inch focal length camera and enlarged to a scale of 1:4,800. 1949 1978 Relief displacement 5.4 8.0 Measurement Errors 1.0 2.0 Tilt 0.6 0.6 Photograph Scale Errors 2.0 3.1 Total Error 9.0 13.7 Calculating the probable error to a 95 confidence interval by use of the following formula: 02 tot = 021 + 022 +023 + 024(Bevington, 1969) where o = the standard deviation of the errors involved. Assume: 2o1 = 5.4 2ol = 8.0 2o2 = 1.0 2o2 = 2.0 2o3 = 0.6 2o3 = 0.6 2o4 = 2.0 204 = 3.1 otot = o21 + o22 + o23 + o24 Otot= (2.7)2+(0.5)2+(0.3)2+(1.0)2 Otot= (4.0)2+(1.0)2+(0.3)2+(1.6)2 otot = 2.9 otot = 4.4 2otot = 5 8 2otot = 8.8 The limit in accuracy for comparing beach change is: 2o/1949-1978/= (5.8)2 + (8.8)2 2o/1949-1978/= 10.5 A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -22- TABLE #3- A Comparison of Field Measurements With Ground Distances Computed from Aerial Photographs Measurements #1 and #2 were taken near Kailua Beach Park. Measurements #3 and #4 were taken at the north end of the beach. The maximum error is 1.1% for' all measurements made Z@,? mb@, M easurement Aerial Photograph % Error #1 159 ft. 158 0.6% #2 538 ft. 4 4 ft. 1.1 #3 78 f t. 78 f t. 0.0% #4 537 f t. 542 f t. 0.9% A M ethod and Selected A pplication f or Using A erial Photos in Delineating Historic Pattern, of Beach Accretion and Retreat -23- DISCUSSION Fifteen transects were established perpendicular to Kailua Beach at approximately 4000 ft. intervals. The exact spacing was dependent on the stable reference points available. The location of these transects is shown on a map for Kailua Beach (Fig. #6). On each transect,- the distance from stable r ce points to the water line and vegetation line was measured over the 3 r observation period. For transects #1 and #2,: data was available only for eight years due to a lack of suitable reference points. For the Ka ilua Beach Park areW ct #13 the map, additional photographs were provided by the Army Co f 0 1: Wineers for 1959,- 1961i 1962: 1966 and 1970. This historic data was combi ff e six flight lines used in this study to draw cumulative movement cur r vegetation and water lines (Fig. V). On the diagram : the results are ith a previous aerial photographic. study for Kailua Beach Park (Noda.' 19 - ximum deviation between any of the data points for the two curves on line is about 14 feet. These deviations are. due to the errors inherent i methods involved as well as different interpretations on the of the land-water boundary on a photograph. Even with the de the two curves show the same historic trends in the position o at e. The exact location of the w is dependent on seasonal and long term changes in the beach profile. Th a better indication of long term beach trends is the position of t etati e. When the cumulative movement curve for the vegetation line red the two water line curves, a very strong coincidence is shown major differences (Fig. #7). For the period f rom 1963 to 1966,- th c he water line was +45 feet while that for the vegetation line s ee e cumulative curves also deviate in the indicated range in beach c he water line curve, the apparent long term range is approximately 15 he vegetation line indicates a historic range of about 134 f eet. Genera line and vegetation, line can be used to determine past long t r prov he seasonal 'fluctuations are small in relation to the 1ong term For ailua Beach Park area, this requirement is satisfied. However some ns of Kailua Beach where -the long term changes are relative t parent trends from the water line and vegetation line are quite dif f ). From the diagram,: the vegetation line appears relatively stable except period from 1957 to 1963. Information obtained on the'water line shows a cons rbly different trend. the net changes in this line are greater than 24 feet for all observation periods from 1949 to 1975. Only for the time from 1975 to 1978 does the position of the water line indicate any degree of stability. Since the location of the water line is affected by seasonal fluctuations of the beacN' the description of long term beach trends in this report is based primarily on vegetation line dala. A Method and Selected Application for Using Aerial Photos in Delineating Hi5toric Patterns of Beach Accretion and Retreat -24- Historic shoreline movement curves for each transect are drawn from six photogr@phic flight lines,*' except for the Kailua Beach Park area.: where eleven flight lines are used. A comparison of cumulative movement curves based on six and eleven data points reveals the problems in determining historic trends from alimited time sample of the beach (Fig. #9). The curves for the eleven observation points document beach changes more accurately. I this example; the total range in shoreline movement has been underestimated sing only six flight lines. However,' the six monitoring points do define al ificant trends in long term beach change. Also, using eleven data points is twice as expensive and time consuming as six. When all factors are conside ms that for Kailua Beach.' an approximate five year monitoring inter a good compromise between economy. and accuracy of results. OAHU 13 14 A 2 12 3 KAI LUA BEACH 4 10 5 8 7 SCALE: 1 inch 950 feet Fig. #6. The location of the transects established at Kailua Beach. @O A H @U- -'(i nfeet) Change Fla Ln C) C_n C) C) C) C) ko Ln C) ko Ln EA C+ C+ C+ m 0 C+ co C+ 0 m m ko CA r- r- CD m C+ Ln =r m %0 00 0 ko @4 Ln ;a m cl, iw to. m oll V) CD ko C.+ cu ko 14 Ln C+ to cX) -9z- luallald PUU UOTla-JZ)Z)V VUD@G 10 @6Jallled DIJOIST14 2UIIUQullacl UT soloqd IleliaV 2uTsrl jol uoiluz)ildd apa a p v p I s PU POLWD V@ v Change (in feet) ci CD CD ko CD CMD m C+ CD a% CD c') (D cu m 0 C+ 14 co C) -LZ- lRaila-d -PUP UOTla'D:)V LIDUag 10 SuJallud :)TJOIST14 2UTjUaUTja(] UT Ja V 2UTSn .101 uoiju:nIdd V papala u soloqd IPT s PU P04law v Distance al ong the transect fin feet) CD Cl . . . . . . . . . C) CD CD to Cn - --I --b! C-) CD 0' C ID 0. C+ 0 CD m (D to w a C+ C+ 0 to M M CD V) C+ C+ 0 0 (D Cr P S -1 CU no =r =7 M a) 0) C+ C+. 0 0 0 :3 U3 to -S -S M CD M -. -- (A IM C a ,j U3 (M (M to m CD (D CD 101 m CD X* C) U2 (a C+ (D X < =r m -h =r C+ C+ (D tD (D M ko i -4 CD (D CD C+ ILO (D W CD 00 --h =3 CD 00 C) CL W -b m I w CD 0 :E M C+ 0) -h C+ -1. r+ -LZ- CD 0 (D CD C+ Ileailald Pule uO'laJ0DV Vleag JO su.]Qllled z)TJOIsTH 2u'lleauTlacl uf s.010qd lle'J.a V 2uTsfl JOJ uoillez)ildd V pajoalaS pule poqia 1N V A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -28- RESULTS Table #4 summarizes the historic changes in the position of th e vegetation line for the fifteen transects. From the data, t several interesting trends are apparent. Within the total littoral cell known as Kailua Beach are three distinct units or subcells. Although the sand transport processes in any of the subcells is dependent on the oithers,t each unit seems to behave as'---parate entity. For the period from 1949 to 1957,i Kailua grew throughout its entire length except for 'the middle portion between s #7 and #9. During the i 0 monitoring interval from 1957 to 1963,i accret evalent 'With especially t- - high growth in the middle section of the beach. It is not obvious why the middle port' f Kailua Beach changed the way it did for these two observation periods. H r,@,,@en the two monitoring intervals are combined,i and net changes compute m _ to 1963,- all transects show the beach growth to be more regular. Thi it w, te an important clue to the beach processes operating at that time. Sin photograph represents only a spot observation,' it may be possible that photographs recorded unstable conditions for the central part of the An examination. of the 1957 photographs does show the shore t orientation abruptly -in this area. During the monitoring interva4i the middle portion of the beach gre Iw about twice as much as realign itself with other sections of the shoreline. For. the next three observa eriods,1 from 1963 to 1978,, an interesting pattern of beach change early from the data. While one end of Kailua Beach is accreting,! the d is I eating. The middle sections tend to remain relatively stable. Thl also supported by the historic ranges in the position of the veget es. During the r terval. from 1963 to 1971,, the southeast of Kailua Beach was in an a le while the'opposite end retreated by as much as'40 feet. For the two o periods from 1971 to 1978,, the trend reversed,: and resulted in si er at Kallua Beach Park while the Kaneohe end of the littoral ce I ahl The c tren rosion and- accretion at opposite ends of Kailua Beach is similar seas hanges on other Hawaiian beaches,; such as on Lumahi Beach (M y and Chamberlain,, 1963). This pattern indicates that sand eroded a he beach is transported to the opposite end. Therefore,i it should be re at any structures designed to horde sand at one end of the littoral cell may rve all down drift sectionsof the beach. Any shifts in the trend of beach change reflect reversals in the direction of long term littoral transport. Two possibilities are presented to account for these reversals. %D %0 NO %D 0 m ou @4 14 aN 4- @4 %D a- :C-c ?@. w (D -3 CA (D +c aQ r (D3 0 %D %D + 14 @4 (7% %A "D 00 w "all z M :3 %D 0 rb OQ OQ (D (D fD 9k) %,D =1 14 14 OQ 00 00 m (A + + 0 C) 4-1 r+ =r fp + '4 OQ CD + + 4- r+ 4-- 00 CD 0 :3 (IN C% + + + 14 f-i 0 14 + r+ + + + a% Kji w 0% 0 v (A 14 + 8 w C) w 4-- 0 I + + w 00 4-- 00 T 0 + CL ON 4.1 @4 -9.1 %D CA + + + a% C) .00 w %D 14 w 00 00 + + + 00 CD 4- hi 44 + w %,D 00 r%) w I I %D K) 14 + + 14 4-- -P 14 a+% %0 C) 00 N C) + + 00 "@4 -6Z- jIeaJj3-d PUU UOIjaJ3:)V.q01eaq JO SUJ;DI112,d OTJOISTH 2UTjLaUIjacj UT "2uTsfl joj suoile:)Tldd a ;D p aV Lila VN v SOTOW IL'T-J v P Pat S'pu PO A Method and Selected Application for Using Aerial Photo, in Delineating Historic Patterns of Beach Accretion and Retreat -30- 1) It has been suggested that the direction of littoral transport varies seasonally for Kailua Beach (Noda; 1977). During the summer months,' strong persistent trade wind waves tend to transport sand to the northwest. In the winter,! sand transport may be to the northwest or southeast depending on the interaction of trade wind waves with North Pacific Swell. According to this concept,i the direction of long term littoral transport would be to the south as -1@ A unusually strong or persistent North Pacific Swell occurred ove i-yearly period. 2) It is also possible that a shift in the n of the trade winds causes the reversals. Since the orienta Beach is almost perpendicular to the northeast trade wi e f luctuations in this wind system would have a pron af fe the direction of littoral drif t. If over a ten year pe the trade winds blew from a more easterly directon than us i ay result at'Kailua Beach Park and accretion at the oppos* e littoral cell. This trend may be reversed if the trad d w from a more northerly direction i when averaged over a y period. Accordin@ to Wentworth (1949),, winds shifted in direction from northeast to east and back to no over a period of - 40 years (Fig. #10). If trade wind riodicity are the rule., then beach changes at Kailua have a natural cycle of 40 years. While the two hypothesis p have been mentioned separatelyl' they are not mutually exclusive. For exam e long term direction of littoral drift may be to the southeast for e wi ave activity accompanied with a northerly shift in the trade winds Since the litto 0 allua Beach are dependent on meteorological factors,;* an accura edki beach changes would require a knowledge of future weather c n He our ability to forecast trade wind directions or North Pacific S is limited,: it should be realized that the historic record for Kailua s a tendency towards cyclic erosion and accretion. Therefore,' th es ccur in the future. This means that trees,, houses or any other sr no be placed on that portion of an accreting beach which may retre ny later as part of the natural cycle. Unfortunately.: this practice t been wed for several sections. of Kallua Beach. For example: I the d from 1949 to 1971 the vegetation in front of transect 128 feet. Within this time lnterval,i two rows of trees were. approximately 95 feet and 40. feet inland of the 1971 vegetati e. Between 1971 and 1978,i the Vegetation retreated about 119 f eet to the position where the 1978 vegetation line was within ten feet of its 1949 location. Needless to say,! many trees fell,in the water. 0 F- Ic0 m ',a ta. (n PA." p) 0 F- z :1 cr (a I.- " 0% CLm cr :3 m 0 C) 00 M 0 C) -1 rip =r 0 03 1-@ (D r 0 v 0) m rt 10 :3 =r 0 m rr N ID FA. 0 rv 0 M 0 M t rv rt. 0rip :r n r? C) U) F@ r- n 0) cr 14 0 " :3 (n M CL 00 m0 m IJ. mn C) :2 B 0-& rr a) 00 :m 1.4n 0 rip 03 03 Pt (D rr 0 9--f 03 cr (n (03 0 CZ) :1m 0 rr :C m 0) :r m C) C16. r? to 03 :3 rt co 0=1 rlr rr = 3 "0) 0 m cr riW 0 0 Mrf (D :3 r? C) =r m =0 727: 1 C3 M r- m CL H (D ry) C-_ pi 03 0 %a :1 0 (is I-- rr M .8 4- 0 -0 *4 @-& .0 'o %< . . C:= 0 C rr - 03 V - 0 m0 @-& m Ph 0I-h cr > IC 0 FA. to 40 40 :3 0 ro (A -ob CL 0 0 0 Ileajlz)-d Pup Uollaj:)DV Llz)le;D@l 10 5UJallled :)TJOISTH 2UTIleaullacl UT aV 2uTsfl jol suoiliez)tidd a a le ql soloqd Ile" V P TDOI S Pu PO a INV A M ethod and Selected A pplication f or Using A erial:Photos in Delineating Historic Patterns of Beach Accretion and Retreat -32- 2) From 1949 to' 1978,; the net change in the position of the vegetation line for transect #8 was +44 feet. During this period a house was built 35 feet inland of the 1978 vegetation line. If the beach retreated to its 1949 positioni this house would be undermined. 3) Between transects #5 and #6,! the vegetation grew about 54 feet over the 30 year observation period. Five houses been built along this stretch and are located from 47 to 40 f ndward of the 1978 vegetation line. 4) Approximately 300 feet south of trans egetatio n grew 61 feet over the 30 year monitoring peri constructed at this location about 32 feet inland of 8 veg ion line. In fact this.house is situated within-10 feet he 1949 land-water boundary. This is an especially precarious posj S' the house is located near the end of the beach where changes 0 ter magnitude. It cannot be predicted whether n of the -beach will retreat to its 1949 position. The cumulative movemen or most of the transects show a general increasing trend (Appendix A). 1 the Kailua Beach Park area showed a general increasing tre rs. until rapid erosion began without any forewarning. Since our kn littoral cycles at Kailua Beach is imperfect it would be wise to evelopment well inland of the most withdrawn historic position o tation line,; as determined by aerial photographs. If this practice I d,,, extensive property damage may be avoided in the near future. For,;' t oric record indicates that Kailua Beach is a dynamic zone which will inue nge through natural cycles of erosion and accretion. A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns of Beach Accretion and Retreat -33- CONCLUSION The use of aerial photographs to document historic shoreline changes is an economical and time efficient method.1 Most of the work can be conducted in the office,: except one field trip should be made to check or obtain ground control. Even then,' the use of aerial photographs greatly reduces the amount of field measurements because ground control can be accur extended by the methods prescribed in this report. Another advantage in aerial photographs is that imagery of the Haw aiiian coastline has been obtai ore f requently in the past 30 years than maps.. charts or surveys have been c erhaps,: the lack of aerial photographic studies for beaches on Hawaii d to the questionable accuracy of the measurements made. In this study,; a method is presented aximum estimated error of about 12 feet for measuring beach changes. Th b d to be an accurate estimate,- as indicated by a comparison of field aphic measurements and by the consistent distances obtained for ne of the beach in the Kailua pilot study. While a 12 foot measUremen n may seem large, this f igure is sufficiently accurate to meet the objedtiv project for two reasons. First any anomalous. measurements can. be checked se the almost infinite amount of ground detail on a photo allows to be established. Secondly.' the extreme ranges in long term ake any accuracy limitations less critical. For examplei the min* his nge in the position of the vegetation line for the Kailua Beach study while the maximum was 146 feet. The methods described in thi rt were applied for a pilot study of Kailua Beach. It was found that tire grew from 32 to 81 feet during the period from 1949 to 1963. Due* xt t 'e monitoring intervals, a pattern of erosion at one end of the bea at the opposite end is clearly shown from the data. From 1963 to I e of Kailua Beach grew by as much as 69 feet while the Kaneo e f tor I cell retreated up to 40 feet. The direction of net littoral dr* t indicated from data for the next two observation periodsi which s o t erosion at'Kailua Beach Park while the north end of the beach grew ide Effecti t of the beach requires information about the long term changes to x c this zone. To actually forecast beach changes may be dif f icult sibl to a number of unpredictable variables such as storms or long ter ather ions. However, by studying historic shoreline movements,: a know ai f the trends; rates and ranges of change Which are possible foe any p ach. These possible changes must be considered whenever proper planni isions are made.@ For example,- development on portions of Kailua Beach in process of an accreting cycle should be avoided because'.beach retreat may result in the future as part of the 'normal sequence. This practice has not been followed for several sections of the beach,, although the historic record shows a definite cycle of erosion and accretion. A Method and Selected Application for Using Aerial Photos in Delineating Historic Patterns'of Beach Accretion and Retreat -34- When the time and cost of an aerial photographic study is weighed against the wealth of information to be obtained,@ it is evident that this methc;d of beach monitoring should be extended to ;ill sections of the coast. This report has shown that aerial photographs may be used for a general reconnaissance as well as for planning purposes and sedimentological studies. 00 1. Based on the Kallua Beach- Studyi: it has be culated that each mile of beach requires approximately 20 man hours a .00 of photographs. BIBLIOGRAPHY Athearn, W.D., and Ronne,C., 1963, "Shoreline Changes at Cape Hatteras: An Aerial Photographic Study of a 17-Year Period": Naval Research Reviews No. 6, Office of Naval Research, Washington, D.C., June 1963, p. 17-24. Bascom,W., 1960, "Beaches": Reprinted from Scientific American, 12p. Bascom, W., 1964, Waves and Beaches: New York, Doubleday, 267 p. Bevington, P.R., 1969, Data Reduction and Error Analysis for the Physical Sciences: New York, McGraw-Hill, Inc., 336 p. Cameron, H.L., 1965a, "Sequential Air Photo Interpretation in Coastal Change Studies": Maritime Sediments, V.1, No. 2, p. 8-12. Cameron, H.L., 1965b, "Coastal Studies by Sequential Air Photography": Canadian Surveyor:V. 19, No. 4, p.372-381. Campbell,J.F., 1972, Erosion and Accretion of Selected Hawaiian Beaches: HIG Rept. 72-20 and UNIHI SEAGRANT T-TR-72-02, 36 p. Chamberlain, T., 1968, "The Littoral Sand Budget, Hawaiian Islands": Pacific Science. V. 22,p. 161-183. Cox, D.C., Gerritsen, F., and Lee, T.T., 1976, "Proposed "Improvement" of Kaimu Beach, Hawaii": In Proceedings of the 15th Coastal Engineering Conference. American Society of Civil Engineers, Vancouver, B.C., p. 1552-1571. Cox, D.C., 1978, Notes on Hawaiian Sand Beach Management: Hawaii Coastal Zone Management Program Technical Supplement No. 12., 23 p. Delaware State Planning Office, 1975, Delaware's Changing Shoreline: Delaware Coastal Zone Management, Working Paper No. 5., 26 p. Dietz, R.S., 1947, "Aerial Photographs in the Geological Study of Shore Features and Processes": Photogrammetric Engineering, V.13, No. 4, p. 537-545. Dollar, S., 1979, Sand Mining in Hawaii: Research, Restrictions, and Choices for the Future: UNIHI-SEAGRANT-TP-79-01,106 p. El-Ashry, M.T., and Wanless, H.R., 1965, "Birth and Early Growth of A Tidal Delta': Journal of Geology, V.73, No.2, p. 404-406. El-Ashry, M.T., and Wanless,H.R., 1967, "Shoreline Features and Their Changes": Photogrammetric Engineering, V.33,No.2, p. 184-189. El-Ashry, M.T., and Wanlessq,H.R., 1968, "Photo 1nterpretation of Shoreline Changes Between Capes Hatteras and Fear (North Carolina)': Marine Geology, V. 6, p.347 - 379. El-Ashry, M.T., (ed.), 1977, Air Photography and Coastal Problems: Benchmark Papers in Geology/38, Stroudsburg, Dowden, Hutchinson and Ross, Inc., 425 p. Fisher, J.J. and Regan, D.F., "Determination of Precision and Accuracy of Photogrammetric Measurements for Coastal Changes of Shoreline (Beach), Duneline and Cliffline": in Tanner, W.F. (ed.), 1978,Standards for Measuring Shoreline Changes: A Report of A Workshop. Published jointly by Coastal Research and Dept. of Geology, Florida State Univ. Tallahassee, Florida, 87 p. Gerritsen, F., 1972, "Hawaiian Beaches": In Proceedings of the 13th Coastal Engineering Conference. American Society of Civil Engineers, Vancouver, B.C., p. 1257-1276. Gerritsen, F., 1978, Beach and Surf Parameters in Hawaii: UNIHI-SEAGRANT-TR-78-02,178 p. Goldsmith, V., Sutton, C.H., Frisch, A., Heiligman, M., and Haywood, A., 1978, "The Analysis of Historic Shoreline Changes": Coastal Zone '78, p. 2819-2835. Goldsmith,V., and Oertel G., "Beach Profiling's in Tanner, W.F. (ed.), 1978, Standards for Measuring Shoreline Changes: A Report of A Workshop. Published Jointly By Coastal Research and Dept. of Geology, Florida State Univ. Tallahassee, Florida, 87 p. Horikawa, K., and Sunamura, T., 1967, "A Study on Erosion of Coastal Cliffs by Using Aerial Photographs": Coastal Engineering in Japan, V. 10, p. 67-83. 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Jr., 1963, Coastal Geology of Hawaii: HIG Rept., 41, 216 p. Moberly, R. Jr., and Chamberlain, T., 1964, Hawaiian Beach Systems: HIG Rept. 64-2, 177p. + Appx. A and B. Moberly, R. Jr., Bauer, L.D., and Morrison, A., 1965, "Source and Variation of Hawaiian Littoral Sand": Jour. Sed. Petrology, V. 35, p. 589-598. Moberly, R. Jr., 1968, "Loss of Hawaiian Littoral Sand": Jour. Sed. Petrology, V. 38, p. 17-34. Moberly, R.Jr., 1975, Beaches: A Component of the Coastal Zone: Hawaii Coastal Zone Management Program Technical Supplement No. 4, 36 p. Moffitt, F.H., 1967, Photogrammetry Scranton, International Textbook Company, 540 p. Moffitt, F.H., 1969, "History of Shore Growth from Aerial Photographs": Shore and Beach, V. 37, No. 1, p. 23-27. Morton, R., "Analysis of Sequential Shoreline Changes": in Tanner, W.F. (ed.), 1978, Standards for Measuring Shoreline Changes: A Report of a Workshop. 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LN Transect #1 150 100 50 Transect #2 F 4a, 100- Fr 4-) cu 50 4J M Transe 4j M C oric ge in vegetation line- 67 ft. 0 C cc range in water line- 68 ft. a) 300 4) 250 200 1950 1955' 1960 1965 1970 1975 1980 x based on Jdne,' 1979, -field measurements -@.`Tncludes June,. 1 �79'", field' measurements Transect #4 historic range in vegetation line- 63 ft. -historic range in water line- 63 ft.: @300 250 S@ 7 200 4J 150 350 Transect #5 historic ra in ve ion line- 57 ft. 4J historic r wat ine- 79 ft. 0 300. 250 200 150 1950 '1955: '1960 19.65 1970 1975. 198( Transect #6' historic range in vegetation line- 56 ft. 250 historic range. in water I i-ne- .69. ft.; 100 4J u 4J Cn 0. Oj to 4-1 ILA Tr his e in vegetation line- 4.0 ft. or in water*line- 73 ft'., 350 300 250 1950 1955 1960 .1965 1970: 1975 Transect #6" historic range in vegetation line- 52 ft. historic range in water'line= 57 ft.' 250 200 150 41m 100 Transe his in egetation line- 54 ft. hi in water line- 56 ft. 300 250 200 1950 1955 1960 1965 1970- 1975 ransect #10 I ange in vegetation line- 50 ft. in water line-,65 ft. 300,- ------ 250- 4J (A 200 . . . . ... .1950 1955 1960 1965 1970 1975 1980 Distance along -th-e..-,transect.,(in,feet) J Pa N) CD CD C) N ko 4h .01 Sam X 4< 0) (D C+ (a (D CD C+ CA 0) C+ 0 C+ Ln 7 00 ICA Distance along the transe'ct in feet) 4t*- 4t:- ul C) C" CD Cn, C) CD -CD Cx sz- CD 0 C+ C+ to C+ C+ CD 0 C+ Co CA Co @4 C) 14 Ln 00 C) 4F A Distance along,the trans'ect (.in f eet,)--.,,--., cn Cn Cl CD C) Ln CD LA rt- 0 Ln -1 m 0 C+ ko Cil m CID m CL C+ U3 fD M C+ 0) CD C+ kO M Co C+ CD CD kc Ul to 00 Distance along the transect (in f.eet) cm U1 CD UI CD C) C) C) CD U1 =r =r CD -S C+ C+ 0 0 W I -S CD 0 C+ =4= 4@b Ln (D CD :E < C+ U3 C+ CYI 0) . - C+ 0 CD :3 14 CO (D %0 ON U1 4:b ON Ln to (D 0) co :3 C) (D 0 C+ C+ 0 (D :Distance al6ng the transect (in (!t) 4-b C> Ul C) Cn .Cl C) C) C) C), C> V) tA C+ C+ 0 0 0 0 Ct Ul Ao m M M M CD ON. C) Ci. Co CO CD C+ CD %0 CD 00 ------ C) I I I I I I I I I I I I I I I I I I Ill ll 11111111111111191111 Folmll@'1 3 6668 14102 9829