1Chapter 7: BeachesChapter 7: Beaches& & NearshoreNearshoreEnvironmentEnvironmentGeneral beach-nearshore profileBasic Beach Types and SedimentsSeasonal Beach CyclesPredicting Erosion and AccretionGeneral BeachGeneral Beach--NearshoreNearshoreProfileProfileGeneral BeachGeneral Beach--NearshoreNearshoreProfileProfileNearshore: includes shoal, break and surf zones up to the ridge and runnel systemLongshore Sand Bars are the main featureGeneral BeachGeneral Beach--NearshoreNearshoreProfileProfileBreaks in the longshore sand bar are usually locations of rip currentsDrawGeneral BeachGeneral Beach--NearshoreNearshoreProfileProfileForeshore: intertidal region of the beach (spring high tide to spring low tide levels)Ridge-Runnel system: small scale bar in lower intertidal zoneRidge-Runnel System: small scale bar in lower intertidal zoneRidge = crestRunnel = troughEphemeral, lasting a few weeksPresent during intermediate stages of beach erosion or buildingMost noticeable during strong west/northwest wind events2Plunge Step: Steep change in slope due to turbulence associated with surging/swashing of wavesDrawGeneral BeachGeneral Beach--NearshoreNearshoreProfileProfileBackshore: extends from the berm crest to the next physiographic feature (dune or bluff toe)Erosional Scarps: sandy beachesStorm Ridges: coarse gravel beachesErosionalScarpErosional Scarps: during winter a beach may contain several scarps across the profileStorm Ridges: coarse beaches (gravel/cobbles etc.) energetic swash builds ridge, no backwash due to percolationGeneral BeachGeneral Beach--NearshoreNearshoreProfileProfileBeach: consists of Foreshore and BackshoreBerm: Crest of the beach approximately spring high tide levelBeach Face: steep sloping section of the beach from the berm to the plunge step, created by wave swash.Basic Beach Types and SedimentsBasic Beach Types and SedimentsDissipative: gentle slope, wave energy gradually dissipated across surfzone. Spilling BreakersReflective: steep slope, surging breakers, wave energy reflects back to open ocean3Basic Beach Types and SedimentsBasic Beach Types and SedimentsBeach Sediment Gradient Beach Typemud Gentle Dissipativesandgravelcobblesboulders Steep ReflectiveSeasonal Beach CyclesSeasonal Beach CyclesAccretionary or Summer Beachmild wave energy and onshore winds transport sand onto the beach.Storm or Winter Beachenergetic wave conditions remove sand from the beach and create offshore bars.Predicting Erosion and AccretionPredicting Erosion and AccretionDeep Water Wave SteepnessGrain SizeSettling Velocity4Predicting Erosion and AccretionPredicting Erosion and