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Technical Report CHL-98-22 July 1998 US Army Corps of Engineers Waterways Experiment Station Three-Dimensional Breakwater Stability Tests at Vale de Cavaleiros Cape Verde by Ernest R. Smith, JeffreyA. Melby Approved For Public Release; Distribution Is Unlimited 3- no.ct\u~ Preparedfor Joint Venture RRI-BCEOM Thecontentsofthisreportarenottobeusedforadvertising, publication,orpromotionalpurposes.Citationoftradenames doesnotconstituteanofficialendorsementorapprovaloftheuse ofsuchcommercialproducts. The findings of this report are not to be construed as an official Department ofthe Army position, unless so desig- natedbyotherauthorizeddocuments. ® PRINTED ON RECYCLED PAPER Technical Report CHL-98-22 July 1998 Three-Dimensional Breakwater Stability Tests at Vale de Cavaleiros, Cape Verde by Ernest R. Smith, JeffreyA. Melby U.S. ArmyCorpsof Engineers Waterways Experiment Station 3909 Halls Ferry Road Vicksburg, MS 39180-6199 Final report Approvedforpublicrelease;distributionisunlimited m :o iCD i Preparedfor Joint Venture RRI-BCEOM US Army Corps of Engineers Waterways Experiment Station WaterwaysExperimentStationCataloging-in-Publication Data Smith, ErnestR. Three-dimensional breakwaterstabilitytestsatValedeCavaleiros, CapeVerde/by ErnestR. Smith,JeffreyA. Melby preparedforJointVentureRRI-BCEOM. ; 79p. : ill. ;28cm.—(Technical report; CHL-98-22) Includesbibliogr—aphicreferences. — — 1.Armourstone CapeVerde. 2. Breakwaters CapeVerde. 3. Seawalls Cape Verde. 4. CapeVerde. I. Melby,JeffreyA. II. UnitedStates.Army. CorpsofEngineers. III. U.S.ArmyEngineerWaterwaysExperimentStation. IV. CoastalandHydraulics Laboratory(U.S.ArmyEngineerWaterwaysExperimentStation) V.JointVentureRhein RuhrIngenieur-GesellschaftmbHandBCEOM SocieteFrancaised'lngenierie. VI.Title. VII. Series:Technical report(U.S.ArmyEngineerWaterwaysExperimentStation) CHL-98-22. ; TA7W34no.CHL-98-22 Contents Preface v — 1 Introduction 1 Background 1 Purpose 3 2—TheModel 6 ModelDesign 6 ExperimentFacilitiesandEquipment 7 SelectedStudyConditions 8 ExperimentProcedures 9 ModelBreakwaterConstruction 12 ReportingModelObservations 13 3— Results 14 Introduction 14 Plan 1 14 Plan 1A 14 Plan IB 16 Plan 1C 16 Plan2 19 Plan2A 19 Plan2B 22 Plan2C 22 Plan2D 22 Overtopping 25 Summary 25 — 4 RiskConsiderations 28 WaveConditions 28 ArmorUnitSelection 28 — 5 Summary 30 Results 30 ToeTrenchConstruction 31 References 33 AppendixA: Photographs Al AppendixB: Notation Bl SF298 List of Figures Figure 1. LocationofCapeVerde 1 Figure2. CapeVerdeIslands 2 Figure3. Existingsitelocationmap 4 Figure4. Existingstructure 5 Figure5. Three-dimensionalstabilitymodel 8 Figure6. Three-dimensionalmodelboundariesandwavegauge locations 9 Figure7. HJ at-21.3mCDversusgeneratorstroke, 13-secwaves 10 Figure8. HJ at-21.3mCDversusgeneratorstroke, 16-secwaves 10 Figure9. HJ at-21.3mCDversusgeneratorstroke, 19-secwaves 11 Figure 10. Elementsofplan 1 15 Figure 11. Elementsofplan 1A 17 Figure 12. Elementsofplans IBand 1C 18 Figure 13. Elementsofplan2 20 Figure 14. Elementsofplan2A 21 Figure 15. Elementsofplan2B 23 Figure 16. Elementsofplans2Cand2D 24 Figure 17. Waveovertoppingattrunk,allplans 26 Figure 18. Waveovertoppingatbreakwaterhead,plan 1 serieswaves 26 Figure 19. Waveovertoppingatbreakwaterhead,plan2serieswaves 27 Figure20. Exampleoftoetrenchconstructedonrockybottom 31 Figure21. Exampleoftoetrenchconstructedonsandybottom 32 IV Preface ThemodelinvestigationoftheValedeCavaleirosbreakwaterreportedherein wasrequestedbyJointVentureRheinRuhrIngenieur-GesellschaftmbH(RRI) andBCEOMSocieteFranchised'Ingenierie(JVRRI-BCEOM)andwascon- ductedattheCoastalEngineeringResearchCenter(CERC)oftheU. S.Army EngineerWaterwaysExperimentStation(WES). InOctober1996,CERC mergedwiththeWESHydraulicsLaboratorytobecometheCoastaland HydraulicsLaboratory. AuthorizationforWEStoperformthestudywas grantedbyCooperativeResearchandDevelopmentAct(CRDA)No.WES-96- CERC-01dated 11January 1996. ThestudywasconductedatWESduringtheperiodJanuary 1996through May 1996bypersonneloftheCoastalStructuresBranch(CSB)ofthe NavigationandHarborsDivision(NHD),CHL,underthedirectionofDr.James R.HoustonandMr.CharlesC.Calhoun,Jr.,DirectorandAssistantDirectorof CHL,respectively;andthedirectguidanceofMessrs.C.E.Chatham,Jr.,Chief ofNHD;andMr.D.D.Davidson,ChiefofCSB. Thephysicalmodelwas designedbyMessrs.ErnestR.SmithandJeffreyA. Melby,ResearchHydraulic Engineers,CSB. ExperimentswereconductedbyMessrs.Smith,WillieG. Dubose,CivilEngineeringTechnician;JohnH.Williams,CivilEngineering Technician;JohnnyHeggins,CivilEngineeringTechnician;andDavidDaily, InstrumentationServicesTechnician,NHD. Thisreportwaspreparedby Messrs.SmithandMelby. LiaisonwasmaintainedwithJVRRI-BCEOMthroughprogressreportsand telephoneconversationsduringthecourseoftheinvestigation. Priortocon- structionofthebreakwatercrosssection,Mr.A.Merrien,France,visited WESduring20to22March 1996todiscussproposedtestconditions. Messrs.MerrienandL.Fischer,Germany,visitedWESon17and 18April 1996 toobserveexperimentsanddiscussalternativebreakwaterplans. Atthetimeofpublicationofthisreport,DirectorofWESwasDr.RobertW. Whalin. CommanderofWESwasCOLRobinR. Cababa,EN. Thecontentsofthisreportarenottobeusedforadvertising,publication,or promotionalpurposes. Citationoftradenamesdoesnotconstitutean officialendorsementorapprovaloftheuseofsuchcommercialproducts. Introduction 1 Background ValedeCavaleirosisasmallportonthewestcoastoftheIslandofFogo, RepublicofCapeVerde. MapsoftheregionandharborareshowninFigures 1 and2,respectively. Theharborismanmade,beingenclosedbybreakwaters extendingfromanaturalcape. Theharborprovidesshelterforlocalfishingand commercialcargovessels,andrecreationalbeachuse. Commercialcargovessels areloadedandunloadedusinglocallighterage. Cape Verde AFRICA Figure 1. LocationofCapeVerde Chapter1 Introduction CP* i * £ * "<? Chapter1 Introduction