UNINTENTIONAL
mangawahi pakiri coastline
location
50km north of aukland
UNINTENTIONAL
mangawahi pakiri coastline
reasons for mining
- sand is high quality and used for construction and glass manufacture
- sand used to replenish other beaches such as mission bay, 2.3mill visitors in 2015
UNINTENTIONAL
mangawahi pakiri coastline
impacts for sediment budget
- operated for 70 years
- currenr rate of extraction at 75,000m3 a year
- outputs of sand are not replaced by inputs at a rate of 5:1
UNINTENTIONAL
mangawahi pakiri coastline
impact on the coastal system
- beaches lacking sediment have become flatter and less affective at absorbing wave energy
- higher energy waves erode beaches causing positive feedback making dunes and spits moire vunerable
- loss of vegetation cover on sand dunes causing more erosion
UNINTENTIONAL
mangawahi pakiri coastline
storm
1978 cyclone bola = breech at mangawhai spit
second breach caused alterd tidal currents and the sedementation of mangawhai harbour
causing the clear blue water to be stagnent and polluted
UNINTENTIONAL
mangawahi pakiri coastline
type of system
closed system, not replenished by fluvial imputs
UNINTENTIONAL
mangawahi pakiri coastline
consequenses
- evidant coastal retreat due to sand extraction and sea level rise
- long term retreat of 35m bt end of centuary
INTENTIONAL
3 shoreline management plans
advance the line - new defences, multi layered
- hold the line - maintain of repair old or broken defences
- no active intervention nothing
INTENTIONAL
2 examples of hard and soft
hard = groynes and seawalls
soft = beach nourishment and dune stabelisation
INTENTIONAL
Felixtowe
why do we need management
( coastal environemt )
- high energy winter waves
- 600km fetch
- lots of sediment imput due to soft lithology
INTENTIONAL
Felixtowe
why do we need management
( economic )
- port of felixtowe deals with 48% of british container trade
- dredge to 15 m to accomodate the largest of ships = generating 60Bn a year
- national stategic asset
INTENTIONAL
Felixtowe
why do we need management
( tourism )
- 800 businesses including hotels, cafes, golf courses, the main draw in the summer is the beach
INTENTIONAL
Felixtowe
why do we need management
( environmental )
- variety of flora and fauna, many species of birds
- languard fort part of british heritage
- Languard is a sight of special scientific interest becasue of its rare vegetated shingle habitat
INTENTIONAL
Felixtowe
management at bawdsey
- Do nothing, important source of sediment, area has little conomic value
INTENTIONAL
Felixtowe
management at cobbles point
advance the line
- lowers the energy imputed into the system
- to reduce the amount of energy in the lee of cobbles point therefore reducing the amount of erosion and transport across the beach
INTENTIONAL
Felixtowe
management infront of the town
- hold the line, reduces the impact of marine process to almost 0 by building a sea wall
INTENTIONAL
Felixtowe
management of the beach
Building both concrete and fishtail groynes at intervals of 20m down the beach, to slow the impact of sediment lost by LSD.
80,000m2 of sediment added to increase beach height and give a more uniform appearance
INTENTIONAL
Felixtowe
management of languard spit
- wooden groynes located in languard spit, ( more env sensitive then rock), to stabelise the spit and encourage deposition
INTENTIONAL
Felixtowe
the unintentional impact
due to dredging
- sediment budget is in deficit due to loss due to dredging and less imputs due to coastal management = spit loosing 6% of mass
