Download pdf - Cost of beach maintenance in the Gulf of Cadiz (SW Spain)

Ž .Coastal Engineering 42 2001 143–153www.elsevier.comrlocatercoastaleng

ž /Cost of beach maintenance in the Gulf of Cadiz SW Spain

Juan J. Munoz-Perez a,), Belen Lopez de San Roman-Blanco b,˜ ´Jose M. Gutierrez-Mas c, Luis Moreno d, Gabriel J. Cuena e

a Demarcacion de Costas en Andalucia-Atlantico, Ministerio de Medio Ambiente, cr Marianista Cubillo, 7, 11071 Cadiz, Spain´b Coastal Department, HR Wallingford, Howbery Park, Wallingford OX10 8BA, UKc Facultad de Ciencias del Mar, UniÕ. de Cadiz. CASEM, 11540, Puerto Real, Spain´

d Ministry of EnÕironmental Protection, Pza. San Juan de la Cruz, srno.-28071 Madrid Spaine SerÕicio de Costas de HuelÕa, Cr Rico, 15 21071, HuelÕa, Spain

Received 3 February 2000; received in revised form 16 August 2000; accepted 7 September 2000

Abstract

Beach erosion problems have been solved by adding sand to the beaches along the Gulf of Cadiz. The Gulf is located inSW Spain between the Portuguese border and the Strait of Gibraltar. During the last decade, more than 12=106 m3 of sandhave been nourished in 38 restoration operations carried out on 28 beaches. The main characteristics of the nourishment

Ž .campaigns year, volume, budget, transport method, sand data, etc. are presented. Location of sand borrow sites anddistance to the beaches are also shown. Monitoring programs have been performed in order to calculate sediment loss rates.These results have been related to the beach length, the berm width and the budget in order to obtain a variety ofrelationships for maintenance cost as, for example, the total annual cost for each beach. This information is very useful whendeveloping a strategy in coastal zone management. Furthermore, at least in reef-protected beaches, small yearly renourish-ments similar to the yearly losses, instead of greater nourishments performed with a periodicity of many years, lead to aneconomical saving, as well as to a better use of the natural resources. q 2001 Elsevier Science B.V. All rights reserved.

Keywords: Beach nourishment; Coastal zone management; Beach erosion; Gulf of Cadiz

1. Introduction

The coastline of the Gulf of Cadiz has been inrecession for at least the last century. Subsidencephenomena, sea level rise or manmade barriers, asgroin constructions like the breakwater built in thePortuguese bank of the Guadiana River mouth, arethe causes.

) Corresponding author. Fax: q34-56-276-449.Ž .E-mail address: [email protected] J.J. Munoz-Perez .˜

Analysis of field data and aerial photographs overthe last half century show that the coastline hassuffered a recession rate of approximately 1 mryearin some points of the Spanish Southwest Atlantic

Ž .coast Munoz-Perez and Enriquez, 1998 .Because of˜the erosion, the Spanish Coastal Authority, in thepast dependent upon the Ministry of Public Worksand presently belonging to the Ministry of the Envi-ronmental Protection, decided to begin a coastalprotection program.

Erosion is caused by a negative sediment budgetand, at the present, adding sand to the physiographic

0378-3839r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.Ž .PII: S0378-3839 00 00054-5

( )J.J. Munoz-Perez et al.rCoastal Engineering 42 2001 143–153˜144

unit appears to be the most natural way to solve theerosion problem. Some beach nourishment projectshave sometimes been complemented with the con-struction of some permeable and short groins ad-justed to the beach profile. This was only carried outwhen an important reduction of the annual nourish-

Žment requirement justified it Munoz-Perez and˜.Gutierrez-Mas, 1999 .

Monitoring the behaviour of several beaches sincethe first nourishment allowed for a comparison withprevious works, as well as to establish real meanrates of erosion for each job and predict renourish-ment requirements in the future. Other countrieshave been monitoring for a much greater length of

Žtime see amongst others, Wijnberg, 1995; Lin and.Sasso, 1996; Shak and Ryan, 1996 , and compila-

tions of information on this topic have also beenperformed. For instance, a database that documentsbeach nourishment episodes, which have occurred on

Ž .the US Eastern shoreline from New York to FloridaŽ .was presented recently by Valverde et al. 1999 .

Also, the economic importance of beaches and theirŽ .tourism has been examined by Houston 1995, 1996 .

The federal spendings for shoreline preservation andthe revenues for the government and benefits for the

Ž .national economy have been compared King, 1999 .Nevertheless, the yearly cost of the different beachnourishment programs is a little published parameteryet. The range of this value could prove to be veryinteresting in providing a better design tool for futurenourishment projects and to decide whether theyshould be carried out or not.

The main aim of this paper is to describe amorphological and economical evaluation of thebeach nourishment maintenance strategy carried outin the Gulf of Cadiz during the 1990s.

2. Data compilation

The coastline which is to be studied is locatedalong the Gulf of Cadiz, facing the Atlantic Oceanon the southwest coast of Spain, between the Guadi-ana River mouth and the Strait of Gibraltar. Ageneral view of the area and the location of the 28beaches, where the 38 nourishments were carriedout, are presented in Fig. 1. The region has a mesoti-dal range with a medium neap to spring variation

Ž .1.20–3.30 m . Most of the beaches are composed ofŽ .fine-medium sand D s250 mm consisting of50

85–95% quartz and 5–15% calcium carbonate. Inmany beaches, the typical profiles intersect a sub-merged reef and, consequently, are not sand rich.Wave decay due to the wave breaking over thesubmerged reef, the changes on the resulting beachprofile shape and the stability of the beach were

Ž .discussed by Munoz-Perez et al. 1999a .˜Wave climate data have been collected by two

waverider buoys included in the Spanish WaveŽ .Recording Network known as REMRO . The first

of these buoys, named ASevilleB, was installed infront of the Guadalquivir river mouth anchored at adepth of y12 m. The second one, named ACadizB,was anchored at a depth of y22 m, 3 miles seawardfrom a rocky shoal in front of the city of Cadiz.Statistically elaborated data are available in the Mar-itime Works Recommendations ROM 0.3–91Ž .MOPT, 1991 .

Geophysical campaigns have been performed overthe entire width of the coast in order to identify

Žsubmerged borrow sand areas Esgemar, 1991; Ge-.omytsa, 1991a,b, 1994 . Soundings of the sea bottom

were carried out to check the thickness of sedimentdeposits. Location of borrow sites and dredged vol-umes are shown in Fig. 2. A large number of surfacegrab sediment samples were also collected to iden-tify the borrow sand characteristics.

A conventional topographic surveying techniquewas employed in the aerial part of the beach. Adifferential leveling with reference to a benchmarklocated in the seaside promenade was performed atthe hour of the spring low tide. It was possible tosurvey up to elevation y1.00 m. Due to the fact thatbathymetric contours were made with an echosounderon boat and differential global position systemŽ .DGPS at the spring high tide, an area of overlapwith the aerial topography relates both surveys to thesame datum or Azero levelB. For a comprehensivedescription about the accuracy of the method, see

Ž .Munoz-Perez 1995 . The total cost of the monitor-˜ing works was US$450,000 during the last decade,only 1.2% of the beach restoration investments.

Currents were also measured. The final aim ofthese measurements being the calibration of themathematical models developed to study differentaspects of the coastline evolution.

()

J.J.Munoz-P

erezet

al.rC

oastalEngineering

422001

143–

153˜

145

Fig. 1. Location of the 28 beaches renourished in the decade 1989–1998.


Fig.

2.L

ocat

ion

ofth

esa

ndbo

rrow

site

sin

the

Gul

fof

Cad

iz.

( )J.J. Munoz-Perez et al.rCoastal Engineering 42 2001 143–153˜ 147

Once the beach restoration was finished, newbathymetric surveys were carried out in the majorityof cases. These were performed once per year for, atleast, a period of 2 years. Hence, profile comparisonscould be made and erosion rates estimated.

3. Results and discussion

Data collected for the 38 beach nourishmentsperformed during the last decade are presented inTable 1. From left to right, the data specified are thefollowing.

v Ž .Date year and name of the beach whererestoration works were carried out. Successiverestorations performed on the same beach are shownby different ordinal numbers. So, Fuentebravia,Fuentebravia II and Fuentebravia III would note thefirst, second and third nourishment projects. Therewere 38 sand-pouring operations accomplished on 28beaches from 1989 to 1998.

v Volume of sand poured in the nourishment,which was generally surveyed in the hopper and isexpressed in cubic meters. Total volume was 12.0=

6 3 Ž10 m with a maximum in Victoria Beach 2.0=6 3.10 m .v Final budget, in US$, where Spanish taxes as

Ž .16% value added tax VAT are not included andcost of hard structures such as groins, when neces-sary, are not considered. All costs were adjusted forSpanish inflation factors and converted to 1999 dol-lars. Global investment was US$37.5=106, that isUS$3.7=106ryear.

v ŽTransport method ground transport by trucks or.maritime dredging by trail suction is specified.

Ground transport by trucks, from adjacent beaches ordunes, was performed to nourish 13 beaches. Thevolume transported was 6.5% of the total volume,while the cost was only the 5.5% with an averagevalue of US$2.7rm3. Distances vary from 0.4 to11.2 km with 4.2 km as the average value. On theother hand, volume dredged had an average cost ofUS$3.1rm3 and an averaged distance of 10.9 kmwithin a range from 0.5 to 35 km.

v The main characteristics of the sediment arealso presented. It refers to the mean diameter, inmicrons, of the borrow sand which is very similar to

the native one. Three different areas can be distin-guished along the coastline according to the grainsize. The western one, between Guadiana andGuadalquivir rivers, has a median grain size diameterwhich varies from 350 to 670 mm with an averagevalue of 450 mm. Sand size is finer betweenGuadalquivir river and the Strait of Gibraltar: D s50

280 mm. A coarser grain size of 1000 mm is presentin Guadalquiton beach, in the Mediterranean Sea.Weight of the silt–clay fraction is negligible, about1.6%. The percentage of the bioclastic fraction, i.e.the part composed of flat shell fragments which are,

Žusually, very quickly transported seawards Munoz-˜.Perez et al., 1999b , is also indicated. This value

varies extensively, from 3% to 32% with an averageof 12.9%.

v The type of profile is specified: reef supportedor sand rich.

v ŽLocation of the borrow site submerged or. Ž .emerged and distance kilometer from the borrow

area to the beach nourishment.Working with the previously described character-

istics and along with the beach dimension, a new setof parameters related to the maintenance manage-ment are developed. These values presented in Table2 are as follows.

v The erosion rate is computed by averaging thelosses after nourishments and based on total beachprofile measurements, throughout a monitoring pe-riod of at least two years. It is expressed in cubicmeters per year. These data are not specified in 14nourishment operations because no monitoring workswere performed.

v Length of the beach where restoration workswere carried out and berm width achieved with thenourishment. Both of these values are expressed inmeters. The block diagram shown in Fig. 3 clarifiesthe meaning of beach length and berm width.

v Sediment loss per year per longitudinal meter,obtained by dividing the yearly erosion rate by thebeach length. Average value is 37.5 m3rmryear.Greatest values correspond to Aculadero, Fuente-

Žbravia and La Pena beaches 58, 90 and 108˜3 .m rmryear, respectively .

v3Ž .Unit cost of sand US$rm , id est, the relation-

ship between the real total budget and the fill volumeof the nourishment. The average value is aboutUS$3rm3 with a maximum of US$6.7rm3.


Tab

le1

Bea

chno

uris

hmen

tin

the

Gul

fof

Cad

izin

the

last

deca

de

Ž.

Yea

rB

each

nam

eV

olum

eT

otal

budg

etT

rans

port

San

dK

ind

ofpr

ofil

eB

orro

war

eaD

ista

nce

km3

Ž.

Ž.

mU

S$

met

hod

DP

erce

ntP

erce

ntsh

ell

50Ž

.m

msi

ltfr

acti

on

1989

Cas

till

aB

each

1,69

0,00

03,

813,

333

Tra

ilsu

ctio

n60

01.

5S

and

rich

Pon

ient

eje

tty

6.3

1990

La

Ant

illa

1,30

0,00

05,

333,

000

Tra

ilsu

ctio

n50

01.

3S

and

rich

Rom

pidi

llo

spit

6.1

1990

La

Cac

huch

a82

,030

505,

406

Tru

cks

300

2.6

8S

and

rich

San

Ped

rom

outh

3.8

1991

La

Cal

eta

41,4

4081

,032

Tru

cks

310

3.6

3R

eef

supp

orte

dC

orta

dura

beac

h1.

419

91V

icto

ria

2,00

0,05

05,

527,

742

Tra

ilsu

ctio

n25

02.

411

San

dri

chan

dC

adiz

Cha

nnel

5.2

reef

supp

orte

d19

91S

ta.

Mar

iade

lM

ar30

6,36

055

7,41

9T

rail

suct

ion

350

1.5

16R

eef

supp

orte

dC

adiz

Har

bour

entr

ance

6.0

1991

La

Pen

a67

,035

216,

774

Tru

cks

230

1.2

29R

eef

supp

orte

dV

alde

vaqu

eros

dune

11.2

˜19

91C

anos

deM

eca

16,1

0339

,914

Tru

cks

230

1.7

10R

eef

supp

orte

dT

rafa

lgar

dune

2.4

˜19

91R

ıoS

anP

edro

23,1

5959

,649

Tra

ilsu

ctio

n22

01

15R

eef

supp

orte

dS

anP

edro

mou

th0.

5´

1992

Reg

la50

2,00

02,

650,

000

Tra

ilsu

ctio

n25

02.

58

Ree

fsu

ppor

ted

Pla

cer

San

Jaci

nto

4.2

1992

Can

osde

Mec

aII

124,

234

263,

619

Tru

cks

230

1.5

12R

eef

supp

orte

dT

rafa

lgar

Dun

e2.

4˜

1992

Fue

nteb

ravi

a75

,000

212,

748

Tru

cks

390

0.3

9R

eef

supp

orte

dR

ota

Har

bour

0.9

1993

Car

men

23,1

5043

,413

Tru

cks

220

0.5

15S

and

rich

Bar

bate

Har

bour

0.6

1993

Pon

ient

e13

1,81

918

7,06

2T

ruck

s39

00.

38

San

dri

chA

tuna

rabe

ach

6.7

1993

El

Pal

mar

18,7

9433

,727

Tru

cks

250

1.2

12S

and

rich

Con

ilet

em

outh

2.0

1993

La

Pen

aII

170,

000

413,

641

Tru

cks

240

131

Ree

fsu

ppor

ted

Val

deva

quer

osdu

ne11

.2˜

1993

–19

94L

aB

arro

sa46

3,60

71,

242,

564

Tra

ilsu

ctio

n29

03.

415

San

dri

chP

lace

rde

Mec

a25

.119

94F

uent

ebra

vıa

II27

5,13

354

0,73

3T

rail

suct

ion

280

2.5

12R

eef

supp

orte

dC

adiz

Cha

nnel

8.1

´19

93–

1994

El

Acu

lade

ro17

2,44

826

7,61

3T

rail

suct

ion

390

0.5

17R

eef

supp

orte

dC

adiz

Cha

nnel

4.5

and

truc

ks19

94L

aH

ierb

abue

na16

,216

40,5

16T

ruck

s22

00.

812

San

dri

chB

arba

teH

arbo

ur0.

419

94C

anos

deM

eca

III

496,

000

1,02

1,93

6T

rail

suct

ion

300

3.5

14R

eef

supp

orte

dP

lace

rde

Mec

a4.

0˜

1994

Fue

nte

del

Gal

lo39

9,00

01,

037,

419

Tra

ilsu

ctio

n23

02

18R

eef

supp

orte

dP

lace

rde

Mec

a13

.019

94Is

laC

rist

ina

330,

000

887,

000

Tra

ilsu

ctio

n35

01.

3S

and

rich

Isla

Cri

stin

aH

arbo

ur4.

119

95L

aB

ota

930,

000

3,18

7,00

0T

rail

suct

ion

670

1.5

-20

San

dri

chP

onie

nte

Diq

ue13

Juan

Car

los

I19

95C

hica

12,7

7840

,516

Tru

cks

230

1.5

32R

eef

supp

orte

dV

alde

vaqu

eros

Dun

e11

.219

95E

lR

ompi

dill

o7,

735

11,5

81T

ruck

s22

01

11R

eef

supp

orte

dR

ota

Har

bour

0.6

1996

La

Cos

till

a19

7,00

094

8,74

6T

rail

suct

ion

380

39

San

dri

chC

adiz

Cha

nnel

11.0

1996

Acu

lade

roII

75,6

2524

0,94

6T

rail

suct

ion

250

3.5

14R

eef

supp

orte

dC

adiz

Cha

nnel

4.5

1996

La

Cos

till

aII

94,5

6629

2,35

1T

rail

suct

ion

350

1.2

8S

and

rich

Cad

izC

hann

el11

.019

96F

uent

ebra

vıa

III

134,

808

351,

675

Tra

ilsu

ctio

n30

03

11R

eef

supp

orte

dC

adiz

Cha

nnel

8.1

´19

96M

azag

on42

5,00

01,

406,

364

Tra

ilsu

ctio

n35

02

San

dri

chH

uelv

aH

arbo

ur7.

2´

1996

Mat

alas

cana

s12

5,00

041

3,63

6T

rail

suct

ion

350

2S

and

rich

Hue

lva

Har

bour

18.3

˜19

97L

aA

ntil

laII

300,

000

2,00

0,00

0T

rail

suct

ion

350

0.3

San

dri

chH

uelv

aH

arbo

ur35

.119

97S

ta.

Mar

iade

lM

arII

60,1

8122

8,38

1T

rail

suct

ion

300

0.3

10R

eef

supp

orte

dC

adiz

Cha

nnel

6.0

1997

La

Bar

rosa

II30

,000

142,

575

Tra

ilsu

ctio

n30

00.

210

San

dri

chP

lace

rde

Mec

a25

.019

98C

ampo

soto

.73

7,00

02,

578,

453

Tra

ilsu

ctio

n30

00.

53

Ree

fsu

ppor

ted

Pla

cer

deM

eca

31.5

1998

Pun

taC

ando

r19

,211

100,

373

Tra

ilsu

ctio

n32

00.

58

Ree

fsu

ppor

ted

Cad

izC

hann

el14

.219

98G

uada

lqui

ton

175,

000

538,

400

Tra

ilsu

ctio

n10

000.

910

San

dri

chG

uadi

aro

mou

th0.

8´


Tab

le2

Mai

nten

ance

cost

ofbe

ache

sin

the

Gul

fof

Cad

iz

Yea

rB

each

nam

eS

edim

ent

Bea

chB

erm

Sed

imen

tlo

ssr

Cos

tM

ater

ial

Mai

nten

ance

loss

leng

thw

idth

beac

hle

ngth

ofsa

ndsu

pply

cost

33

3Ž

.Ž

.Ž

.Ž

.Ž

.m

rye

arm

mm

rye

arr

mU

S$r

mV

olum

erbe

ach

Vol

umer

dry

Per

unit

ofP

erun

itof

Tot

al3

32

Ž.

Ž.

Ž.

leng

thm

rm

surf

ace

mr

mbe

ach

leng

thdr

ysu

rfac

eU

S$r

year

2Ž

.Ž

.U

S$r

year

rm

US

$rm

1989

Cas

till

aB

each

100,

000

2000

110

502.

2684

57.

711

317

.422

6,00

019

90L

aA

ntil

la50

,000

3500

5014

4.10

371

7.4

5930

.220

5,00

019

90L

aC

achu

cha

560

356.

1614

64.

219

91L

aC

alet

a36

020

1.96

115

5.8

1991

Vic

tori

a70

,000

3500

7020

2.76

571

8.2

5523

.019

3,20

019

91S

ta.

Mar

iade

lM

ar30

,000

600

4550

1.82

511

11.3

9120

.754

,600

1991

La

Pen

a65

,000

600

1810

83.

2311

26.

235

020

.020

9,95

0˜

1991

Can

osde

Mec

a75

03

2.48

217.

2˜

1991

Rıo

San

Ped

ro37

08

2.58

637.

8´

1992

Reg

la35

,000

1500

3823

5.28

335

8.8

123

46.7

184,

800

1992

Can

osde

Mec

aII

750

242.

1216

66.

9˜

1992

Fue

nteb

ravi

a72

514

2.84

103

7.4

1993

Car

men

5000

1200

34

1.88

196.

48

12.5

9400

1993

Pon

ient

e70

023

1.42

188

8.2

1993

El

Pal

mar

800

41.

7923

5.9

1993

La

Pen

aII

85,0

0080

030

106

2.43

213

7.1

259

17.2

206,

550

˜19

93–

1994

La

Bar

rosa

45,0

0012

0040

382.

6838

69.

710

126

.112

0,60

019

94F

uent

ebra

vıa

II65

,000

725

6090

1.97

379

6.3

176

12.5

128,

050

´19

93–

1994

El

Acu

lade

ro35

,000

600

4058

1.55

287

7.2

9111

.154

,250

1994

La

Hie

rbab

uena

4000

730

35

2.50

227.

414

17.9

10,0

0019

94C

anos

deM

eca

III

26,5

0075

070

352.

0666

19.

473

19.5

54,5

90˜

1994

Fue

nte

del

Gal

lo52

,000

1200

3043

2.60

333

11.1

113

28.7

135,

200

1994

Isla

Cri

stin

a40

,000

1800

4022

2.69

183

4.6

6012

.310

7,60

019

95L

aB

ota

50,0

0042

0040

123.

4322

15.

541

18.7

171,

500

1995

Chi

ca12

025

3.17

106

4.3

1995

El

Rom

pidi

llo

4000

800

25

1.50

104.

87

7.5

6000

1996

La

Cos

till

a15

,000

1200

2013

4.82

164

8.2

6039

.272

,300

1996

Acu

lade

roII

11,0

0060

020

183.

1912

66.

358

19.8

35,0

9019

96L

aC

osti

lla

II12

0010

3.09

797.

919

96F

uent

ebra

vıa

III

62,0

0072

531

862.

6118

66.

022

315

.716

1,82

0´

1996

Maz

agon

30,0

0015

0028

203.

3128

310

.166

33.1

99,3

00´

1996

Mat

alas

cana

s30

,000

700

1843

3.31

179

9.9

142

33.1

99,3

00˜

1997

La

Ant

illa

II20

0040

6.67

150

3.8

1997

Sta

.M

aria

del

Mar

II10

,000

600

1217

3.79

100

8.4

6332

.237

,900

1997

La

Bar

rosa

II12

003

4.75

258.

319

98C

ampo

soto

.45

,000

3000

2815

3.50

246

8.8

5230

.915

7,50

019

98P

unta

Can

dor

200

145.

2296

6.9

1998

Gua

dalq

uito

n50

030

3.08

350

11.7

´


Fig. 3. Block diagram clarifying some concepts of a beach nourishment.

v Restoration volume divided by the beach lengthŽ 3 .m rm .

v2Volume requirements to get 1 m of berm or

dry beach.v Maintenance cost in different units: price per

year for every meter length beach, price for everysquare meter of berm and finally, the annual mainte-nance cost of each beach.

Despite the importance of the annual total costparameter, the most adequate parameter to comparecosts between different beaches is the annual mainte-

Ž .nance cost per unit of beach length US$ryearrm .If one of the main goals of a nourishment scheme isto maintain the dry surface of the beach for touristexploitation, this parameter is very useful in decidingwhere to best invest public funds. In our particularcase, these values normally range from US$7 toUS$142ryearrm with an average of US$100r

yearrm and only La Pena and Fuentebravia restora-˜tions exceed US$150ryearrm reaching a maximumof US$350ryearrm.

It is noteworthy that the biggest erosion rate wasobserved directly after a big nourishment in reef-sup-

Ž .ported beaches. As Munoz-Perez et al. 1999a˜showed, no equilibrium beach profile is possiblewithin a distance less than 30–100 m from the edgeof the reef. So, as you feed more sediment, moresand is transported quickly seawards. Perched orreef-protected beaches, whose profiles are not sandrich, loose sand rapidly when the volume dumpedsurpasses the geometric limits set down by the mor-

Žphological characteristics Munoz-Perez et al.,˜.1999a . It is also worth noting the fact that a reduc-

tion in the volume of the successive restorations ofthe beaches of Santa Maria del Mar Beach and of

ŽAculadero Beach from 306,000 to 60,181 and from


3 .172,448 to 75,625 m , respectively was related to asubstantial reduction in the annual rates of erosionŽfrom 30,000 to 10,000 and from 35,000 to 11,000

3 .m ryear , while no significant changes in waveclimate were observed during the monitoring period.The former figures were obtained by profile compar-isons carried out with the yearly bathymetric surveysperformed during the 2 years ensuing the nourish-ments.

For economical studies, it would be important toknow whether a relationship exists between size of

Ž .job total cubic meters of project and unit price. Inorder to accomplish this, Fig. 4 was prepared withthe purpose of displaying the actual cost in US$rm3

versus the nourishment volume, making a clear dis-tinction between the contributions made by truck andtrail suction. In the first place, it is noteworthy to

state that the volumes transported by truckloads donot surpass 200,000 m3. Their price, with only oneexception, fluctuates between 1 and 3 US$rm3 al-though bearing no defining trend. On the other hand,two separate groups can be defined amid the nour-ishments carried out by trail suction dredgers. Thefirst one reaches up to 600,000 m3 of sand. Thoughthe costs are very spread out, a simple linear fit bythe least squares method shows a decreasing ten-dency. The same tendency, the lessening of costs asvolumes increase, though subject to a slighter disper-sion rate, can be observed in the existing rangebetween 600,000 and 2,000,000 m3.

Fig. 5 shows the volume of sand placed on thebeaches per year and, also, the annual cost of thenourishment in the last decade. The rather largenourishments and investments in the initial years are

Ž 3.Fig. 4. Cost of sand US$rm in different beach restorations versus their nourishment volumes.


Ž 3. Ž . Ž .Fig. 5. Sand nourishments m and investments US$ per year in the Gulf of Cadiz 1989–1998 .

because of the need to replace the existing deficit. Inlater years, the need for sand has reduced and stabi-lized about 1=106 m3 of sand corresponding toUS$3=106ryear.

4. Conclusions

The data collected from the 38 beach nourishmentcampaigns that have been carried out on 28 beaches

Ž .in the Gulf of Cadiz SW Spain during the lastdecade are presented. Within the values of the differ-ent parameters demonstrated, it is important to pointout that the average annual volume nourished tomaintain more than 400 km of coastline was 1.2=

106 m3. This imposed an averaged cost of US$3.75=106 a year, which has to be related to the enor-mous income that tourism yields in the area everyyear.

The cost of transport by truck is slightly lowerthan the transport by dredger and dumping through

Ž 3.tubes US$2.7 against US$3.1rm , although thevolume carried by the truck was only 6.5% of thetotal.

The relationships between the costs and the geo-metric characteristics of the beach suggest manyparameters, all of them of great help when attempt-ing to make decisions on sustainable and economicalmaintenance of the beaches within the framework ofcoastal zone management. Nevertheless, the annual


maintenance cost per unit of beach length appears tobe the most useful parameter when comparing thedifferent investments done. Its average value be-comes US$100ryearrm, but with a great range ofscatter: from US$7 to US$350ryearrm.

Substantial decrease in the sand volumes nour-ished within successive restorations carried out oncertain beaches led to drastic reductions in the yearlyerosion rates. In addition, it may be concluded that,at least in reef-protected beaches, small yearly re-nourishment, similar to the yearly losses, instead ofgreater nourishment performed with a periodicity ofmany years, leads to economical savings, as well asto a better use of the natural resources.

Finally, it is noteworthy to point out that a de-creasing tendency in the cost per unit of the sandpoured can be acknowledged as the nourishmentvolume increases, this being specially noticeable inthose volumes superior to 600,000 m3.

Acknowledgements

The authors wish to acknowledge the contributionof the Federal Coastal Authority of the Ministry ofEnvironmental Protection, for their support through-out the data collection campaigns. The valuableremarks of Professor William Allsop are greatlyappreciated. This work was partially funded by theNational Office of Science and Technology throughcontract Mar 98r0796.

References

Esgemar, Gabriel J., 1991. Marine geophysical study between theCape of Trafalgar and the Carnero Promontory, DireccionGeneral de Costas. Ministerio de Obras Publicas y Trans-

Ž .portes, Madrid, Ref 00-373, 5 vols. in Spanish .Geomytsa, 1991a. Marine geophysical study between the Puerco

Ž .Tower and the Castle of San Sebastian Cadiz , DireccionGeneral de Costas. Ministerio de Obras Publicas y Trans-

Ž .portes, Madrid, Ref 00-372, 5 vols. in Spanish .

Geomytsa, 1991b. Marine geophysical study between the Cape ofŽ .Trafalgar and the Puerco Tower Cadiz , Direccion General de

Costas. Ministerio de Obras Publicas y Transportes, Madrid,Ž .Ref 00-371, 5 vols. in Spanish .

Geomytsa, 1994. Marine geophysical study on the coasts of Ceuta,Melilla and Cadiz between the San Sebastian Castle and theGuadalquivir river mouth, Direccion General de Costas. Min-isterio de Obras Publicas, Transportes y Medio Ambiente,

Ž .Madrid, Ref 28-25, 5 vols. in Spanish .Houston, J.R., 1995. The economic value of beaches. The CER-

Cular vol. CERC 95-4. US Army Engineers Waterways Exper-iment Station, Vicksburg, MS, pp. 1–4.

Houston, J.R., 1996. International tourism and US beaches. ShoreBeach 64, 3–4.

P. King, 1999. The Fiscal Impact of Beaches in California. Report29 pp. Public Research Institute. San Francisco State Univ.

Lin, P.C., Sasso, R.H., 1996. Influence of nearshore hardbottomon regional sediment transport. Proc. 25 ICCE. pp. 3642–3651.

Ž .MOPT Ministry of Public Works , 1991. Recommendations forMarine works 0.3-91. Annex I: Maritime Climate in theSpanish Littoral. Secretaria General Tecnica. Centro de Publi-

Ž .caciones. Madrid. in Spanish .Munoz-Perez, J.J., 1995. Reliability of bathymetries and granu-˜

lometries; their application to the measurement of VictoriaŽ .Beach Cadiz . III Jornadas Espanolas de Ingenieria de Costas˜

y Puertos. Serv. Public. Univ. Politecnica, Valencia, pp. 639–Ž .651 in Spanish .

Munoz-Perez, J.J., Enriquez, J., 1998. Littoral dynamic of a˜complete physiography unit: Sanlucar-Rota. Rev. Obras Publi-

Ž .cas 3375, 35–44 in Spanish .Munoz-Perez, J.J., Gutierrez-Mas, J.M., 1999. Typology and effi-˜

ciency of groins built for the improvement of stability on thebeaches of the Atlantic littoral in the province of Cadiz. Bol.

Ž .Geol. Min. 110–111, 53–66 in Spanish .Munoz-Perez, J.J., Tejedor, L., Medina, R., 1999a. Equilibrium˜

beach profile model for reef-protected beaches. J. Coastal Res.Ž .15 4 , 950–957.

Munoz-Perez, J.J., Gutierrez-Mas, J.M., Parrado, J.M., Moreno,˜L., 1999b. Sediment transport velocity by a tracer experiment

Ž .at Regla Beach Spain . J. Waterw., Port, Coastal Ocean Eng.Ž .125 6 , 332–335.

Shak, A.T., Ryan, J.A., 1996. San Gabriel river to Newport Bayerosion control project, Orange County, California. Proc. 25ICCE. pp. 4650–4663.

Valverde, H.R., Trembanis, A.C., Pilkey, O.H., 1999. Summaryof beach nourishment episodes on the US East Coast Barrier

Ž .Islands. J. Coastal Res. 15 4 , 1100–1118.K.M. Wijnberg, 1995. Morphologic behaviour of a barred coast

over a period of decades. PhD Thesis. Faculteit RuimtelijkeWetenschappen, Universiteit Utrecht. Netherland.