ABOUT IMPACT OF SILTATION AND RECLAMATION ON AQUATIC HABITAT

2. Silt
• Silt is granular material of a size between sand and clay.
• Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water
(also known as a suspended load) and soil in a body of water such as a river.
• It may also exist as soil deposited at the bottom of a water body, like mudflows from landslides.
• ISO 14688 grades silts between 0.002 mm to 0.063 mm (sub-divided up into three grades fine, medium
and coarse 0.002 mm to 0.006 mm to 0.020 mm to 0.063 mm).

3. • Siltation, or sans, is water pollution caused by particulate terrestrial clastic material, with a particle size
dominated by silt or clay.
• It refers both to the increased concentration of suspended sediments and to the increased accumulation
(temporary or permanent) of fine sediments on bottoms where they are undesirable. Siltation is most often
caused by soil erosion .
• Siltation is a process by which water becomes dirty as a result of fine mineral particles in the water. When
sediment, or silt, is suspended in water.
• Increases in the amounts of suspended sediments in streams are caused by erosion of the stream bed in
the upper parts of the stream and by sediment inputs from the catchment areas, which can be greatly
augmented by erosion from agricultural and mining areas.

4. • Sedimentation processes have various impacts on aquatic ecosystems (NEWCOMBE & MAc DoNALD
1991, RYAN 1991).
• Increased sediment loading of aquatic systems comprises the most important off-site impact of soil
erosion (Pimentel et al., 1995; Waters, 1995), which itself represents one of the most important
environmental and social problems facing humanity (Pimentel et al., 1995; Helming, Rubio &
Boardman, 2006; Pimentel, 2006).
• Human-induced soil erosion has resulted in an increase of 2.3 billion metric tonnes of sediment being
transported by rivers globally every year (Syvitski et al., 2005). Only 1.4 billion metric tonnes of this
actually reaches coastal waters.
• Increased delivery of sediment to aquatic systems can, however, also be a consequence of other
human activities, including, for example, mining, urban development, construction and the presence of
roads (Gruszowski et al., 2003; Motha et al., 2004; Rijsdijk, Bruijnzeel & Sutoto, 2007).

5. • Although the delivery of sediment to lakes has reduced in some regions owing to the introduction of
sediment control programmes and improved soil conservation practices (seeLal, 2001), excessive
sediment loading remains one of the primary forms of anthropogenic disturbance of aquatic
ecosystems in both tropical and temperate regions (Ryan, 1991; Waters, 1995; USEPA, 2000; Parkhill
& Gulliver, 2002).
• In addition to affecting natural lake systems, the retention of eroded sediments in reservoirs is a major
environmental, social and economic concern globally as high sedimentation rates reduce hydropower
efficiency and viability, increase costs of dam maintenance and water treatment and have important
consequences for water supply, fisheries and tourism (Clarke et al., 1985; Robertson & Colletti, 1994;
Pimentel et al., 1995).
• Multiple and varied effects of high sediment loads on aquatic ecosystems have been documented (see
reviews by Cordone & Kelley, 1961; Chutter, 1969; Bruton, 1985; Clarke et al., 1985; Lloyd, 1985;
Appleby & Scarratt, 1989; Newcombe & MacDonald, 1991; Ryan, 1991; Kerr, 1995; Harvey & Pimentel,
1996; Wood & Armitage, 1997).

6. • Lakes comprise highly complex systems with the overall effects of increased sediment loads likely to
be determined by interactions among numerous physical, chemical and biotic factors. Indirect effects
are, therefore, likely to be highly important, with increased sediment loads likely to affect both bottom-
up and top-down ecological processes.
• Fine sediments in the water column increase turbidity, limit light penetration,and potentially reduce
primary productivity with resultant impacts on the rest of the food chain (Davies-Colleyand
others1992).
• Any water containing silt is turbid in nature and hence require treatment before usage. This treatment
will result in increasing the cost of water distribution and hence making it unaffordable.

7. • When parameters like volume and velocities are disturbed, either due to lower gradient (entering into
plain reaches) or encroachment in flood plain, widening of the channel (braiding of river streams),
suspended silt particles in the river water settle down. This is called siltation.
• Erosion of soil and rock particles by water from poorly maintained catchment during erosive phase of
river regime and addition of extra sediment and silt load through human activity in flood plains disturb
the natural sediment regime of the river and cause it to create unexpected deposition .
• Siltation in rivers may or may not be accumulative; whereas sedimentation in reservoirs is generally
accumulative. The sediment inflow rate into a particular reservoir is, in general, a function of the
watershed characteristics such as drainage area, average land and channel slope, soil type, land
management .

8. • Physical and hydrological characters of the catchment, such as slope, land use, land cover,
urbanisation, agricultural practices, deforestation and forest degradation etc.,
• Intensity of erosion in the catchment (sheet, rill, gully and stream channel erosion) including
over-exploitation of minerals,
• Quality, quantity and concentration of the sediment brought down by the river,
• Size, shape and length of the reservoir and operation strategies .

9. • The origin of the increased sediment transport into an area may be due to erosion on land or activities in
the water.
• In rural areas, the erosion source is typically soil degradation by intensive or inadequate agricultural
practices, leading to soil erosion, especially in fine-grained soils. The result will be an increased amount
of silt and clay in the water bodies that drain the area.
• In urban areas, the erosion source is typically construction activities, which involve clearing the original
land-covering vegetation and temporarily creating something akin to an urban desert from which fines
are easily washed out during rain storms.
• In water, the main pollution source is sediment spill from dredging, the transportation of dredged material
on barges, and the deposition of dredged material in or near water.

10. The characteristics of fine sediment in rivers at a global scale are highly variable,reflecting variations in
climate,catchment geology,basin scale,and sediment natural variations in river flow.It is possible to identify
two main sources of sediment available to the river:
1. , which are principally derived from the bed and banks of the stream and its tributaries.
The supply of sediment from channel sources is strongly related to stream discharge and the stability of the
channel bed and banks.
2. with in the catchment, such as bare soils that are susceptible to erosion
(Grimshawand Lewin1980). The supply of sediment from non channel sources may be highly variable
depending on its mode of production and transport into the stream.

12. • Decreased transmission of light through the water column is among the most important of the physical
effects of increased sediment loads on aquatic ecosystems (Ellis, 1936). The absorption and scattering of
light by suspended particles reduces the compensation depth, below which light intensity is insufficient to
sustain photosynthesis, thus diminishing the volume of water supporting primary production (Kirk, 1985;
Lloyd, 1985; Lloyd, Koenings & LaPerriere, 1987; Krause-Jensen & Sand-Jensen, 1998; Whalen et al.,
2006).
• Lloyd (1985) reported sharp reductions in the compensation depths of different Alaskan lakes and minor
variations in turbidity with dramatic changes in their productive volumes.
• Increased mineral turbidity has also been shown to attenuate blue light more rapidly than red light (Ellis,
1936; Grobbelaar & Stegmann, 1976; Kirk, 1979), and to increase the frequency of light fluctuations
(Grobbelaar, 1985), with considerable implications for photosynthetic production (Kirk, 1985).

13. • Differential light attenuation may also be responsible for the modification of behavioural responses of
lacustrine biota to those processes driven by photoperiod and light intensity. Cuker (1987) observed, for
example, a significant diurnal shallowing of vertical migration of the zooplankton in a lake as a consequence
of increased mineral turbidity.
• Increased sediment loads or resuspension of deposited sediments can cause considerable reductions in
both oxygen availability (Bruton, 1985; Appleby & Scarratt, 1989) and rates of water column reaeration
(Alonso, McHenry & Hong, 1975).
• Increased mineral turbidity also influence the heat budgets of lakes through the absorption of heat by
suspended particles (Kirk, 1985) or by increased reflection of sunlight back to the atmosphere (Clarke et al.,
1985), and can, therefore, depending on the nature of the suspended sediments and lake morphology,
cause water temperatures to increase (Ellis, 1936) or decrease (Clarke et al., 1985).

14. The first two types are of particular
concern because their small size
permits suspension in water and
transport by tidal currents.

15. EFFECTS ON BIOTA
The impact of sedimentation on producers in streams has far reaching consequences since
periphyton and aquatic macrophytes form the base of the food chain and any deleterious impacts will
probably also be manifested in the invertebrate and fish communities. Fine sediment suspension and
deposition affects producers in four mainways:
1. by reducing the penetration of light and, as a result, reducing photosynthesis and primary productivity
within the stream (Van Nieuwenhuyse and La Perriere 1986)
2. by reducing the organic content of periphyton cells (Cline and others 1982,Graham1990)
3. by damaging macrophyte leaves and stems due to abrasion (Lewis1973)
4. by preventing attachment to the substrate of algal cells, and by smothering and eliminating periphyton and
aquatic macrophytes (Brookes 1986).

16. • Light attenuation by inorganic turbidity decreases the fraction of light absorbed by photosynthesising
organisms in lakes (Tilzer, 1983). This has been shown to reduce the density, growth rates and
production of lake phytoplankton considerably (Seki et al., 1980; Lloyd et al., 1987; Søballe & Kimmel,
1987; Cuker, Gama & Burkholder, 1990; Dokulil, 1994; Guenther & Bozelli, 2004a).
• High turbidity and sedimentation rates have been shown to reduce the density (Robel, 1961; Moss,
1977), growth rates (Lewis, 1973), photosynthetic activity (Chandler, 1942), regeneration (Spencer &
Ksander, 2002) and maximum depth of colonisation (Canfield et al., 1985) of aquatic plants as well as
causing considerable physical damage to their leaves (Lewis, 1973).
• High mineral turbidity has also been shown to reduce the standing crop of periphyton, although this
can be concurrent with increased photosynthetic efficiency (Van Nieuwenhuyse & LaPerriere, 1986).

17. • High suspended sediment concentrations have been associated frequently with altered assemblage
composition and reduced abundance and biomass of lake zooplankton (Adalsteinsson, 1979; Hart, 1986,
1987, 1990; Lloyd et al., 1987; Koenings et al., 1990; Cuker & Hudson, 1992; Jack et al., 1993; Dejen et al.,
2004).
• Reduced rates of zooplankton population growth in turbid conditions have been found to be a consequence
of both decreased survivorship and fecundity with increased suspended sediment loads (Kirk & Gilbert,
1990; Kirk, 1992), with juveniles generally more susceptible than adults (Kirk & Gilbert, 1990).
• A decline of 70% in the net reproductive rate of Daphnia ambigua with experimentally increased suspended
sediment concentrations was recorded (Kirk & Gilbert, 1990).
• Experimentally increased concentrations of suspended sediments have been shown to reduce rates of both
zooplankton feeding and the incorporation of carbon into their tissues by up to 99% (Arruda et al., 1983;
Hart, 1988; Kirk, 1991b; Bozelli, 1998).

18. • Rates of ingestion also varied significantly with the size of suspended particles, with significant
variability found among species in their responses to particles of differing size (Kirk, 1991a).
• Experimental work (Koenings et al., 1990) has, however, found that increased suspended
sediment concentrations can reduce cladoceran feeding efficiency significantly, owing to
considerable overlap between the sizes of their algal food and inorganic particles in suspension.
• Increased turbidity has been shown to enhance the dominance of rotifers over cladocerans in
lakes (Kirk, 1991a).
• A number of ciliates (Jack & Gilbert, 1993; Jack et al., 1993), rotifers (Kirk & Gilbert, 1990) and
daphnids (Schulze et al., 2006) are highly sensitive to increased suspended sediment
concentrations.

19. • Benthic assemblages have been shown to be impacted more negatively by increased sediment loads than
either planktonic or nektonic assemblages (Iwata, Nakano & Inoue, 2003).
• Field studies in lakes (Lloyd et al., 1987; Alin et al., 1999; Donohue, Verheyen & Irvine, 2003; Donohue &
Irvine, 2004a) have found that increases in sediment loading tend to reduce the abundance of benthic
invertebrate assemblages considerably.
• These alterations frequently include considerable reductions in species richness (Cohen et al., 1993; Alin
et al., 1999; Donohue et al., 2003; Donohue & Irvine, 2004).
• Donohue et al. (2003) found that benthic invertebrate communities in Lake Tanganyika (Africa) showed
extremely low resistance to and resilience after (sensu Harrison, 1979; Pimm, 1991; Power, 1999)
experimentally increased sediment loading.

20. • Balata, Piazzii (2007) has found that increased sedimentation of inorganic particles can decrease the
variability of benthic communities among sites significantly, probably owing to increased homogeneity
of habitat structure.
• Experimental work and field surveys (Donohue & Irvine, 2004b; McIntyre et al., 2005) have found that
anthropogenically increased sediment loading can alter the size structure of populations of benthic
invertebrates significantly.

21. • Massive fish mortality has been reported owing to anoxic conditions caused by the resuspension of
deposited sediments in shallow lakes (Bruton, 1985), relatively high concentrations of suspended
sediments coupled with chronic exposures appear to be required to cause direct mortality in fish
(Wallen, 1951; Herbert & Merkens, 1961; Herbert & Richards, 1963; Bruton, 1985; McLeay et al., 1987).
• High turbidity levels diminish feeding efficiency and, growth rates of visually predatory fish by reducing
the reactive distance between predators and their prey at the time of detection (Gardner, 1981; Berg &
Northcote, 1985; Barrett, Grossman & Rosenfeld, 1992; Gregory & Northcote, 1993; Miner & Stein,
1993; Rowe & Dean, 1998).
• Under moderate turbidity and high ambient light conditions, however, feeding performance and growth
rates are frequently higher than those in clear water (Boehlert & Morgan, 1985; Barrett et al., 1992;
Miner & Stein, 1993; Bristow & Summerfelt, 1994; Bristow, Summerfelt & Clayton, 1996; Utne, 1997;
Utne-Palm, 1999, 2002).

22. At least five ways in which high concentrations of fine sediment adversely affect lotic fisheries have been
identified.
1. by adversely acting on the fish swimming in the water and either reducing their rate of growth, reducing their
tolerance to disease or killing them; lethal concentrations primarily kill by clogging gill rakers and gill filaments
(Bruton1985)
2. by reducing the suitability of spawning habitat and hindering the development of fish eggs,larvae and
juvenile fish (Chapman1988,Moring1982)
3. by modifying the natural migration patterns of fish (AlabasterandLloyd1982)
4. by reducing the abundance of food available to fish due to a reduction in light penetration and as a result
photosynthesis,primary production,and a reduction of habitat available for insectivore prey items (Bruton1985,
Doegand Koehn 1994,Grayand Ward 1982)
5. by affecting the efficiency of hunting, particularly in the case of visual feeders (Bruton1985,Ryan1991).

23. • Davis (1960) studied the effects of turbid sea water on the hatching and growth of hard clam larvae. Egg
development was retarded at silt concentrations of 0.75 gram per liter (750 ppm) and development
ceased at concentrations of 3.0 - 4.0 g/l. (3,000 - 4,000 ppm).
• Loosanoff and Tommers (1948) found that the pumping rate of oysters was reduced 57 per cent at silt
concentrations of 0.1 gm/l. (100 ppm).
• Ellis (1936) stated that freshwater mussels remained closed 75 per cent to 95 per cent of the time when
exposed to erosion silt.
• Loosanoff (1961) reported that dead and dying oysters in turbid waters always contained large quantities
of silt in the gills.
• Korringa (1952) stated that winter kill in oysters was heaviest during rough weather and turbid waters.
Oysters weakened by the prolonged cold temperature could not rid their gills of mud and therefore died.

24. • High silt loads greatly reduce the amount and character of the light penetrating into the aquatic
environment and it affects the group of aquatic plants whose photosynthetic organs are submerged
below the water surface, chiefly because of the reduction in total light.
• Many South African rivers appear naturally to have a fairly high turbidity due to high intensity nature of
rainfall,and this may well contribute to a natural relative sparseness of submerged aquatic macrophyte
communities of Potamogeton sp. and Aponogeton sp. over much of the lengths of these rivers.
• Small increase in turbidity in marginal or near marginal aquatic light climate as a result of a naturally high
turbidity will be of immense significance to plants and this increased silt loads as a result of land use
practices has caused in recent time a major decline in the abundance of submerged aquatic macrophyte
vegetation, accounting for their present relative spareness.

25. • Millard and Scott (1953) have pointed to the limiting effects of poor light penetration and continual
mud deposition upon plant growth .
• The coarse material tends to accumulate around the plants and with the seasonal decline in
current speeds there is a further deposition of finer materials, often resulting in the burial of the
aquatic community.
• Since the fall in water level marks the onset of the reproductive phase of many aquatic plants,
smothering of the plant body by fine sediments may be sufficient to prevent reproduction, causing
ultimately the death of the plant population of the area.

26. 1. Pre-constructing measures
They are those measures which are adopted before and during the execution of the project. They are as
follows:
• Selection of Dam Site- The silting depends upon the amount of erosion from the catchment. If the
catchment is less erodible, the silting will be less. Hence, the silting can be reduced by choosing the
reservoir site in such a way as to exclude the runoff from the easily erodible catchment.
• Construction of Check Dams- The sediments inflow can be controlled by building check dams across the
river streams contributing major sediment load. These are smaller dams and trap large amounts of coarser
sediments. They however, prove to be quite expensive.
• Vegetation screens- This is based on the principle that vegetation trap large amounts of sediment. The
vegetation growth is, therefore, promoted at the entrance of the reservoir as well as in the catchment.

27. 2. Post-constructing measures.
These measures are undertaken during the operation of the project-
• Removal of Post Flood Water- The sediment content increases just after the floods; therefore, attempts
are generally made not to collect this water. Hence, the efforts should be made to remove the water
entering the reservoir at this time.
• Mechanical stirring of the Sediment - The deposited sediment is disturbed by mechanical means, so
as to keep it in a moving state, and thus, help in pushing it towards the sluices.
• Adopting Erosion Control and Soil Conservation Measures in the Catchment Area - This includes all
those general methods which are adopted to reduce erosion of soil and to make it more and more
stable. They may include: plantation, control grazing, terracing benching, cover cropping like grassing
and contour binding, etc. This method is found to be the most effective method for controlling siltation.

28. The method of minimizing siltation may be of two types - one that is required for the catchment and the
other in the river itself.
(a) The method to be adopted in catchment may include- An effective and permanent method of sediment
control is soil conservation in the catchment, which includes the following practices;
• Afforestation and forest management
• Regrading and grassland management
• Cultivation practices, such as crop rotation, increasing organic matter, mulching, seasonal cover crops,
contour cultivation, strip cropping and terracing.
• check dams- contour bunding and trenching.
• Appropriate land use controls for protecting areas of importance.

29. (b) The method to be adopted in river itself-
• Storage reservoirs
• Desilting basins.
• River training works such as bank protection, etc.
• River training works for local sediment control e.g. submerged vanes, bed bars, bundalling, etc.
• Delineation of flood plains with different risks of flooding/ erosion and appropriate land use regulations
and policies.

30. SUKHNA LAKE IN CHANDIGARH
• Yadvinder Singh (2001) elaborated that due to high rate of water-soil erosion there has been a change
in the profile of stream beds with the result during rainy season the water often overflows their banks
and floods the adjacent lands.
• It has also been shown by him (Y. Singh, 1996) between Satluj and Ghaggar rivers have experienced
vast change due to environmental change consequential to high rate of developmental boom
experienced by Chandigarh, as reflected by the fact that these hills suffer from high rate of soil loss
averaging 367.5 tons/ha/yr.
• The man-made Sukhna Lake brought into existence through blocking of the water flow in the Sukhna
originating from these hills by raising of stone-cum-earthen embankments, is experiencing siltation over
the years.
• Naturally, the water flowing into the lake is heavily loaded with silt. Thus due to higher run-off there is
accelerated pace of erosion in the catchment areas of the seasonal stream tributaries of Sukhna
resulting in the higher rate of sedimentation in the reservoir of Sukhna Lake and stream beds. Naturally,
the silt deposited year after year in the lake bed reduces the water storage capacity, depth, water
spread area and submergence area at lake level.

31. FARAKKA BARRAGE
• Farakka barrage-about 2.6 km long- was constructed in the year 1967 across river Ganga with the
objective of forcibly diverting flow from the parent river Ganga to its tributary river Hoogly. The river
Hoogly (initial stretch of which is known as Bhagirathi) was drying up due to silting of it’s off take point
at a place called Jangipur (at a distance of about 40 km downstream of the barrage), resulting in
gradual reduction of fresh upland flow from Ganga.
• During the pre-barrage period, the main course of Ganga between Rajmahal and Farakka was along
the right bank and the stretch was almost straight. After the barrage was constructed, the main course
of the river upstream of barrage has shifted towards the left bank and that on the downstream side it
has shifted towards right bank .
• Continued erosion of the river upstream and downstream of the barrage has resulted in colossal loss of
agricultural and household properties and subjected the poor people living on the banks to
unimaginable sufferings.

32. • Uncontrolled erosion and deposition process in the vicinity of Farakka barrage has resulted in
development of meanders and its migration towards Malda district in West Bengal ( on left bank) resulting
in flooding, loss of life, agricultural lands and other properties on both the banks If the erosion continues, .
• A study has been carried out in three villages (Chakla, Vorotpur, and Kismotchakla) of Monirampur Thana
of Jessore District and two villages (Pakuria and Diara mathpara) of Kalaroa Thana of Satkhira District,
Bangladesh.
• The result of the study reveals that adverse impact of coastal embankment project, low flow due to
Farakka barrage, local obstacles, high salinity, growth of profuse water hyacinth, etc., in the river
facilitated deposition of sediment in the river and gradual siltation created a hump on the riverbed.
• During the period 1994-2001 the cross-sectional area, width, average depth and conveyance capacity of
the river decreased, which deteriorated the drainage capacity of the river and created severe water
logging.

33. • Mouth of 12% rivers has silted up due to continuous siltation. Number of Dead River is increasing
gradually due to siltation. Siltation also accelerated the emergence of sand bars and decreased depth
in many rivers (Rahman, 2005 a).
• The Kopotaksha is the tributary of the Bhairab. The Bhairab River already dried due to siltation as an
outcome of flow reduction in the Ganges as a result of water withdrawal. Since upstream part of the
Bhairab River is died, the Kopotaksha also now is a nearly dead river with no flushing action as well
water pressure from the upstream. But siltation has been continuing for years during high tides. As a
consequence the Kopotaksha River has been causing flooding in the entire region every year causing
suffering of millions of peoples (Anonymous, 2009).
• The weak flushing power in the Ganges favored the formation of siltation in the river over the years
which change the overall river morphology (NFPCSP, 2009).

34. PAVAN DAM IN MAHARASHTRA
• Silt has been accumulating in the dam for around 50 years,This led to a decrease in the water storage
capacity of the dam..
• Desilting was carried out in the dam for the first time in the year 2000. A total of 39,200 cubic metres of
silt was removed from the dam due to which the storage capacity increased by 3.92 lakh litre. The dam
was built around 1970 on Pavana river.

35. Siltation In Odisha’s Paradip Harbour
• One of the major problems encountered by the shoreline harbours along east coast of India is siltation
in the form of littoral drift.
• Over the years, siltation and erosion have led to reduction of basin depth which is resulting in frequent
boat capsize. Massive silt deposit is also obstructing release of Mahanadi’s floodwater into sea thereby
exposing river bank settlements to the threat of flood.
• The basin depth should be at least five metre for hassle-free movement of fishing vessels and boats.
However, the depth has now been reduced to two metres due to heavy deposit of sand. The
department has sought suggestions of Indian Institute of Technology-Kharagpur on dredging the
Mahanadi river mouth in Paradip to bring down siltation.
• The depth of the harbour is dipping day be day. Massive silt deposit on the Mahanadi river mouth
poses threat to the trawlers and vessels. The 500 metre long river water channel, which the vessels
sail through before making their way into the sea, has undergone severe siltation.

36. MUMBAI
• The highest number of land reclamations took place in the past forty years in the city.
• Prior to Independence, approximately 35 sq km of land reclamation was carried out by the colonial
administration for linking the erstwhile seven islands of Worli, Parel, Mahim, Mazagaon, Bombay, Little
Colaba and Colaba.
• Many projects (Mumbai Trans Harbour Link Project ) have been proposed in the Concept Plan for future
development of the larger Mumbai Metropolitan Region (MMR) and have become controversial due to their
impact on ecology and local residents.
• Unscientific and haphazard measures adopted for reclaiming land and the changing nature of land because
of increase in built-up area have adversely impacted the city’s ecology, particularly its coastline; it caused
perennial flooding.
• The Mumbai Trans-Harbour Link project was envisaged about 35 years back. The project aims to connect
the City of Mumbai with Navi Mumbai. Once completed, MTHL will be the longest sea bridge in India
covering a total length of 21.8 kilometres.

37. Adverse impacts on Mumbai’s ecology
• Depletion of vegetation, transformation of soil cover to concretised landscape has reduced
permeability, increased run-off, which has been one of the primary causes for the flooding in Mumbai
during monsoons; creeks are increasingly getting narrower and shallower due to silt and increase in
built-up area, causing blockage of the natural drainage systems of the city.
• With the High Tide Line (HTL) shifting to the inter-tidal zone associated with reclamation, mangroves
and mudflats are gradually wiped out as is seen in the Lokhandwala environs; the creeks and channels
tend to get shallower and narrower, affecting drainage outflow.

38. contd...
• The Mumbai Trans Harbour Link project has also harmed the
Mumbai's birds area in Sewri which destroyed an important
flamingo habitat, mudflats and mangroves.
• “BirdLife International and BNHS have designated the area as Important Bird Area (IBA) and have also
identified it as a potential Ramsar Site, and apart from the flamingos, they also witness migration of
about a lakh birds of different species.
• The bird species found in the area include greater and lesser flamingos, black headed ibis, brown
headed gull, whiskered tern eastern imperial eagle and black tailed godwit. The flora in Sewree
includes 53 species of vascular plants, 10 mangrove species and 13 mangrove-associated species .

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Aquatic Life
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40. • Wantzen.K.M.,Effects of siltation on benthic communities in clear water streams in Mato Grosso, Brazil,
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18-25
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Rejuvenation