Infrastructure development in coastal marine environment involves dredging, which creates lot of bad impacts on biodiversity such as corals, benthic fauna, water quality etc.
What should be the mitigation measures?
1) Dredging should be undertaken only during the mid days within a phase of the new & the full moon days.During these days,the tidal amplitude is the lowest in the particular moon phase.As the water movement is the least,siltation on marine biota can be minimised.
2) Grabbing of benthic substratum entails lesser disturbance of mud particles as compared to its deposition at some place away from its original source through the action of water movement.Instead,the gathered material can easily be used in the manufacture of cement,as is being done in some parts of the world.
You have very corrently phrased how to minimize the effect of dregging. There are advance technologies available now, one such was use of suction and CSD technology where there is very limited effect due to increased suspended particulate and contaminant resuspension and redistribution.
In order to minimize the impact of dredging, it is should be (combined of Chandravadan Trivedi and Saif Uddin):
1. To choose suitable time to dredging. They are time minimize move around of dredging point (neap tide) or moving along way from protect zones. For ex.: there are protect zones in North of dredging point. If in flood tide, flow and sediment move to the south of dredging point, that time is good time to make dredging.
2. To choose advance technology for dredging. For ex. CSD technology
3. Use a good model to simulate hydrodynamics and sediment transport condition could be the mitigation measures.
Yes, I agree with Drs. Trivedi, Saif and Vinh, regarding the combined approach. Off course it will minimize the impact and also reduce the suspended particulate matter to save the coral reef and other associated flora and fauna in coastal and marine environments.
Before thinking about how to reduce the effect of dredging, it seems to me first : to think of preventive measures, :
Legeslative measures, especially those related to offshore protocol
Technical measures, coast monitoring and identification of vulnerable areas to be protected. delineate the impact of dredging through the use of radioactive tracers or other methods
Obviously, the point which you have raised is valid and practical. We must look all the angle to control the effect of dredging within the legislative frame using standard protocol.
It would be really wise taking into account all of these interesting comments, but I wonder if we should not think of quantifying the possible damage first. A methodology applied to a specific case can be checked in "Turbidity and Other Effects Resulting from Trafalgar Sandbank Dredging and Palmar Beach Nourishment" by Roman-Sierra et al
Of what economic import is the dredging of the coastal environment. This is the prime concern to environmental economist. What does it interprets to in terms of Gross Domestic Product? Employment, residences and perhaps tourism. The costs should have a pay back possibilities.
Tina Mertens (Belgian Coastal Division) made an economic assessment of different options including dredging. See: "Storm impact and cost predictions along the Belgian coastline". The European FP7 project ConHaz puts it into perspective, the Ferrara workshop proceedings are available online (conhaz.org).
Thanks for valuable suggestion. I will try to down load the economic assessment report. I feel definitely it will be very useful. I also take opportunity to wish all of you a very happy and prosperous new year 2014.
Timing is an important component, as Vu Duy Vinh states above, but it is not just timing of tides; but timing as in time of year and what protected fauna is using the area to be dredged.
The first and most important step in minimizing coast degradation is to precisely know what is the cause of degradation and determine whether it is natural or man made. A good monitoring network is needed to define the type, pattern, extension, and distribution of degradation. Only when these parameters are known, the proper solution or remediation methods can be suggest and subsequently timing of remediation.
Off course good monitoring network or proper implementation methodology is very important. In addition to that what fauna is going to be protected as suggested by Dr. Nash is also equally important.
Http://www.thecrownestate.co.uk/media/466210/aggregate-dredging-and-the-marine-environment.pdf
look at CSD (cutting suction dredger) they create minimum impact on the suspended particulate concentration and turbidation.
Only during the middle of the day on the new and full moon days should dredging be done. The tidal amplitude is at its lowest on these days for the particular moon phase. The impact of siltation on marine biota can be reduced since there is little water movement.
Regarding the importance (or lack thereof) of the turbidity generated by sand dredging for beach nourishment, please see the study performed by Roman-Sierra et al. (2011). Turbidity and other effects resulting from Trafalgar sandbank dredging and Palmar beach nourishment. Journal of Waterway, Port, Coastal, and Ocean Engineering, 137(6), 332-343.
- Badges
- Science topic
- Similar topics
- Correction