Coastal Land Scapes and Change PDF

# Coastal land scapes and chenge ## The coasted zone - A restricted enviroment - Wave action is concentrated within narrow limits confined to the zone between the highest point reached by storm tides and the lowest experienced by springtides ## The Littoral zone - Includes adjacent land areas an...

# Coastal land scapes and chenge ## The coasted zone - A restricted enviroment - Wave action is concentrated within narrow limits confined to the zone between the highest point reached by storm tides and the lowest experienced by springtides ## The Littoral zone - Includes adjacent land areas and shallow parts of the sea just offshore. ### Marine Processes - Most influend | Terrestrial Processes | Backshore | Foreshore - inter-tidal or surf zone | Nearshore - beyond the breaker zone | Offshore - influence of waves | |---|---|---|---|---| | Cliffs (or dunes) | Usually above the influence of the waves unless after deposition | Inter-tidal or surf zone | Beyond the influence of the waves | Processes | - Deposition (Storm bedrock) - Max. spring tide - High tide - Low tide - Breakpoint bar - zone of breaking waves - Sand - Storm pebbles berms, sand runnels - Beach shingle and ridges (ridges) - Ettrution - Longshore bars ## The littoral zone streches at into the Sen and on to the shore. The cost is constantly changing because of the dynamic intecation between the processes openting in the sees, Ocean and on land - Short term: waves, daily tiles, season stormy - Long term: Sea levels or climate change ## Divided into Sectiong, Backishore and foreshere. - Areas where greatest human activity activity occures, and processy Such as erosion, deposition and mess movement. - Backshore - Above high tide level only affected by exceptionally high tidy and major Stormy. ## The coastel System ### Inputs - Provide the energy to drive the System - Merine (waves, tides) - Atmosphere (weather, climate cheye, Soler) - Land (rock type, tectonic activity) ### Processes - what happens to create the output - Weathering (breaking down material) - Mass movement (movement of surfue meteric) - Frosion - Transportation - Deposition ### Output - The landform created from the process. - Erosional landforms (arch, steek, Stump) - Depositiond landforny (Spint, benches) ### Dynamic equilibrium - How the coased System oppotes. A sediment cell where inputs coul and outputs are in a constant state of change but stay in bellence. ### Negative feedback - Lessens any charge that cold have happend. Will bring back to the equilibrium. ### Positive Feedback - exagents the charge making the system more unstable. Bringing away from the equilibrium. ### Processes | Merine | Marine erosion dominated | Sub-aerial process dominated | Terestriel "weethering | |---|---|---|---| | Erosion | Steep face | Curved slope | Mass movement | | Transportation | Active undercutting | Lower angle face | More gentle sloping clifl | | Deposition | Limited cliff base debris | Accumulated debris | | | Jogged G | | | | ## uerosion ### Erosion Resistance - Clastic or crystalline - Ls igneous or metamorphic rockys with Crystal structue. - Sedimentary rocks cemented together. - Crystalline are much more erosion recitant - Geological Sorvetee - If rocles have joints, creeks or folds they are weckend and much mre vunerable to erosion. ### Discordant coastlineg - When the kayes of hard rock run perpendicular to the sea. - Result in boys and heedlends, where the Softer rock is eroded leaveing the hol rock jutting out. - Headlend-high cave energy - cave direction - cave crest - Water is deeper in bey then headland. - Wave refrection - when waves approch the coastine Thees not a reguler Shape and bend becomin more perrellel to the coastline. - AS Each cocre reaches the coopt it dreges in the shallow water cohich meerd it Slo by the headland but doesn't in the by сеть the bend. - oveell effent of refretion is that ie conentely on the Headend creating the powerful wowy on the - Umaller were cresty inte Dey increasing deposition hy thee is Sand inbeys. ### Concordant castling - When Rock Strite sons Perallied to the Sea with a layer of had role protecting en Soft rock. - P weekness in the hard rock gets erodel by hydraulic action - Breaks through hard rock into Syft rock and quickly erodies the soft rock, erecting **COVE FORMATION**  - Intrid weekness in the hard rock ### Cliff profiles - Are mostly impected by the angle of the dip, Cowhích củy the Rock Sorote is tecniny. | Horizontal dip | Seaward dip, high angle | Seaward dip, low angle | Landward dip | |---|---|---|---| | Vertical or near vertical profile with notches reflecting strata that are more easily eroded.| Sloping, low angle rock layer facing the sea; vulnerable to rock slides down the dip slope. | Profile may exceed 90° producing areas of overhanging rock; very vulnerable to rock falls. | Steep profiles of 70-80 producing a very stable cliff with reduced rock falls. | | | | | | | Weak strata | Slide blocks | Rock debris | | **Figure 8.9 The influence of dip on cliff profiles** - Rock Strata - Runs Horizontel - Runs Steeply - Runs Slightly but leans back - Bedding plake linto the sea down into towardy land. - et base is exposed to a Vunerable to the Sea - Rock Slides Results in an overheng-> - very Steble with limited rock felly. - hydrolic action - Shelloc eliff - Bedding planes not exposed. - cliff will get enole Collepse. - underect the Bedding pleny - Steep cliff Nothing, to overhey - Wave cut notch not exposed - Wevect pletform profile. - Steep and Vertiele So more resistent ## How lithology affect erosion resistence **1) Mineral composition** - Some rocks contain reactive mines which are easily brocken down by chemical weathering. **2) Rock class** - Sedementry rocks (eig. Sandstone, limestone) are clestie, meaning they are made of sedementry particles Cemented together. - Sedermentry 'roels thet are held together in unconsolidated (bolder cig) - dy are elled Ignious rocks (eg granite) and metemurphie (eq. merble) are crystelline end held togeth with chemical bonds. - This makes them much harder to erode. **3) Structure** - Rocles with joints or faults or heve cir Spece (Porous) weather and erode rapidly. - Dip of rock strota also maks a differnee ## Rock Types - Igneos - Erode and weathe very slow resulting - in CSI structure. - formetive fromunten solidified lava - Metamorphie-Herd and resistent bescue of crystelive Strustee - less resistent then Sedimentry becase crystels are lined up making them weeken - Foru formed fom Igneos rody being exposed to heat and pressure - Sedimentry-formed from compection of Sediment, Herder the rocle from longer compaction - Softer sedimentary Podes erode quite quickly Sherry harder - cen quitte be quiclover - Jänts now Slowenty or quickly it con is ended. ons - onconsolidated-Made of sedementory rock cemented oft gether by easily decodel. - very soft and ## Importance of vegetation - Helophytes - Con tollorde sit ote being Subregel at high tide - pless cert - Concordant - xerophytes - con tollerete very dry conditiong (Sand dunes) - metron gress - beach erss ## Sand dunes | | | | | |---|---|---|---| | Saltation | Pioneer | Slowing | Much moble | | Blow Send | Helphotes | 'Spiecies (moredeposition) | | | Vertical accretion | Mobile dunes | | | | | 100m | 200 m | 300m | | | Yellow | Fixed dunes | Grey -Sol | **Figure 8.15 Cross-section across sand dunes showing plant succession** | | | | |---|---|---| | Poor cooter retention | Vegetation colleets Sedement, Gross gets taller catching more Sedement | orgenie metter, HUMUS Hold more cooter Hes nutrience. | | | xerophtes - long roots Stabelise sedement making more Seccue | | ## Selt Mershes **Vegetation succession (Time)** | | | | | |---|---|---|---| | Also collects more Sedenent. | Tidal inlet (mudflat) | Low marsh | High marsh | | Algee grows on meel binding it togethe | Spring high tide | Cordgrass | Sea lavenders Sea asters | | Mean high tide | | | Soil fertility improves Reduced salinity Reduced seawater flooding | | Lowride | | | Marsh uplands Oaks and shrubs | | | | | | | roots begin to Stebelis the mul and collet more from estuary | | | | | | | | -S developed Soil profile, only Subregel once or toy ayeer | | | | Cordgrass continers cospet of vegetation hold med togetto Potecting Coast from erosion | | |