9.6 Other Attributes of Riparian Ecotone Affecting
the Pollutant Removal Efficiency
The knowledge of the hydrogeomorphic regimes has been ascertained as the key
limitation in the management and restoration of degraded riparian ecotones (Shaw
and Cooper 2008). The study of riparian system as a whole requires an understanding of the geomorphic structures and processes that form the bed sediments and
maintain flow pathways through them. Further Engelhardt et al. (2012) suggested
that it is important to ascertain the relationship between watershed lithology, geomorphology and riparian vegetation for the development, management and restoration of riparian vegetation. Thus, the hydrogeomorphology of the watershed also
plays an important role in the pollutant removal activities of the riparian ecotones.
9.6.1 Geomorphology of the Riparian Ecotone
There are various geomorphological attributes associated with riparian ecotone.
Morphologically the riparian ecotones differ from other upland features as they
receive drainage from large contributing areas, characterised by shallow groundwater table and relatively low slope gradients. The literature suggests that geomorphological attributes affect the pollutant removal functionality of riparian ecotone in two
ways: (1) direct and (2) indirect. Certain features, viz. sediment size, sediment load,
slope, soil structure, subsurface drainage pattern, etc., of the riparian ecotone affect
the pollutant removal, posing direct affect. Indirect effects include the structure, type
and distribution of riparian vegetation, which in turn are determined by the geomorphological traits of the region.
The geomorphology of the watershed regulates the movement of both water and
sediment, through watershed into the channel and via channel network (Engelhardt
et al. 2012). The capacity of riparian ecotone to remove pollutants increases if the
flow across the watershed is not canalised rather distributed across wide areas
(Polyakov et al. 2005). Further, the slope of the zone is also an important determinant of pollutant trapping efficiency of the ecotone (Jin and Römkens 2001).
Another topographic feature of importance in determining the buffering capacity
of riparian ecotone is convergence factor, which is the ratio of active area of the
riparian buffer to the total area (Polykov et al. 2005). Active area of the riparian
buffer according to Polykov et al. 2005 “is the portion of buffer through which
runoff flow from the upslope occurs”. A low convergence value is indicative of
dissected relief, gully and steep valley floors, and higher values (value close to 1)
indicate towards plain conditions (Polykov et al. 2005).
The riparian soil-holding capacity, soil type, soil water content, soil particle size
and soil aggregate density affect the pollutant removal capacity of the buffer
(Munoz-Carpena et al. 1999). The properties of riparian ecotone to trap sediment
decrease with reduction in sediment size (Lee et al. 2003). If the riparian ecotone is
9 Riparian Ecotones: An Important Derivative for Managing River Pollution
213
the Pollutant Removal Efficiency
The knowledge of the hydrogeomorphic regimes has been ascertained as the key
limitation in the management and restoration of degraded riparian ecotones (Shaw
and Cooper 2008). The study of riparian system as a whole requires an understanding of the geomorphic structures and processes that form the bed sediments and
maintain flow pathways through them. Further Engelhardt et al. (2012) suggested
that it is important to ascertain the relationship between watershed lithology, geomorphology and riparian vegetation for the development, management and restoration of riparian vegetation. Thus, the hydrogeomorphology of the watershed also
plays an important role in the pollutant removal activities of the riparian ecotones.
9.6.1 Geomorphology of the Riparian Ecotone
There are various geomorphological attributes associated with riparian ecotone.
Morphologically the riparian ecotones differ from other upland features as they
receive drainage from large contributing areas, characterised by shallow groundwater table and relatively low slope gradients. The literature suggests that geomorphological attributes affect the pollutant removal functionality of riparian ecotone in two
ways: (1) direct and (2) indirect. Certain features, viz. sediment size, sediment load,
slope, soil structure, subsurface drainage pattern, etc., of the riparian ecotone affect
the pollutant removal, posing direct affect. Indirect effects include the structure, type
and distribution of riparian vegetation, which in turn are determined by the geomorphological traits of the region.
The geomorphology of the watershed regulates the movement of both water and
sediment, through watershed into the channel and via channel network (Engelhardt
et al. 2012). The capacity of riparian ecotone to remove pollutants increases if the
flow across the watershed is not canalised rather distributed across wide areas
(Polyakov et al. 2005). Further, the slope of the zone is also an important determinant of pollutant trapping efficiency of the ecotone (Jin and Römkens 2001).
Another topographic feature of importance in determining the buffering capacity
of riparian ecotone is convergence factor, which is the ratio of active area of the
riparian buffer to the total area (Polykov et al. 2005). Active area of the riparian
buffer according to Polykov et al. 2005 “is the portion of buffer through which
runoff flow from the upslope occurs”. A low convergence value is indicative of
dissected relief, gully and steep valley floors, and higher values (value close to 1)
indicate towards plain conditions (Polykov et al. 2005).
The riparian soil-holding capacity, soil type, soil water content, soil particle size
and soil aggregate density affect the pollutant removal capacity of the buffer
(Munoz-Carpena et al. 1999). The properties of riparian ecotone to trap sediment
decrease with reduction in sediment size (Lee et al. 2003). If the riparian ecotone is
9 Riparian Ecotones: An Important Derivative for Managing River Pollution
213