Riparian buffer are the rows of
grasses or trees planted along the bank of rivers and streams. It is one of the agroforestry systems.
Riparian buffers act as the interface between adjacent terrestrial and aquatic
ecosystems. They are designed to protect the river or stream banks, control
flood and minimize the non-point aquatic pollution.
Planting zones: Riparian buffer zoned is divided into
sub zones from land towards aquatic bodies as upland zone, transitional zone,
overbank zone, bank zone and toe zone. Large trees and shrubs are planted in
both upland zone and transitional zones. In the overbank zone, Small to medium size shrubs is found. Plants with flexible stems and creeping stems
including glass are plant in the bank zone so that plant are not damaged by the
extend flood. Emergent plant species
including sedges are found in the toe zone. Large trees are not planted near
zone aquatic body because they are not able to tolerant to large flood.
Buffer width:
The width of the riparian buffer is the major important factor that
affects the effectiveness of the buffer. Welsch has recommended that width of
the riparian buffer should be 90feets on both sides of the river. But width of
the buffer depends on the adjacent land area and land uses. Small stream with
limited input from adjacent land area should have a small buffer width. But
large stream with large input from adjacent area should have a large buffer
width to protect the stream. Adjacent lands may be used for agriculture,
commercial or residential area. Agricultural
lands with good management and maintain requires narrow width buffers. Types
and composition of soil also determines the width of the riparian buffers. Soils
with well drained have high rate of infiltration so it reduces the runoff.
Therefore it requires riparian buffer with narrow width. But poorly drained
soils have low rate of infiltration so it increases the runoff. Therefore it
requires riparian buffer with wider width.
Plant section: characteristics of the river or
stream bank determine the plants that needed to grow. Most of the plant cannot
survive and grow within a certain range of environmental conditions such as pH,
soil air, soil moisture, and soil type and soil texture. But some are able to
grow in extreme conditions including water logged conditions, acidic or basic
pH. Some grow well even in sandy soil where the moisture and nutrient retention
is relatively low. Therefore the plants that are planted in the riparian buffer
zone are able to tolerate water logged conditions, excess nutrients and
sediments and even withstand in sandy or clay soil. A mixture of pants that
offer fruits, fuel, fertilizer, timber, medicine and nesting places for birds
and other animals can be selected.
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Riparian
buffer zones help to enhance quality of aquatic ecosystems while giving other kind
of ecological, economic and social benefits as follows.
Flood control: Riparian buffers act as obstacle
for incoming water through the surface of the land towards the streams. Thereby
it slows down the surface runoff. The root systems of trees and grasses in the
riparian buffers help to lower the river flow velocity. Their extensive root
systems soak up the water in large quantity. Thereby it reduces the risk of
flood. As significant flood is required for the maintaining of flood plains, refrain
buffers help to keep the flood at moderate level.
Trap sediments: Runoff from the poorly managed
agricultural land brings lot of excess sediments. These sediments tend to
deposit at the bottom of aquatic bodies. Thereby continuous addition of sediments
decreases the available depth for aquatic life. These sediments deposits in the
gill of the fishes which kill them. Pesticides, nutrients and heavy metals also
bind and come with sediments so excess nutrients causes eutrophication in
aquatic ecosystems. Pesticides and heavy metals tend to go through food webs
and accumulate in plant and animal bodies which results in serve health
problems or detrimental effect on the animal in the top of the food webs.
Excess sediments are trapped by the extensive root systems of shrubs, grasses
and trees in the riparian buffers .but when sediments is serious problem,
larger portion of the total buffer system hat to be planted with grasses which
are more effective in slow down flow of incoming water and trap the sediments.
Control pollution: Nitrogen and phosphorus are the
primary nutrients for aquatic plants and algae. But excess nutrients cause the
sudden increase of the algal growth. It is referred to as eutrophication.
Eventually eutrophication is able to kill the all aquatic life and convert the
ecosystem into dead. So trees and shrubs in the riparian buffer are important
to eliminate the excess nutrient from the incoming water. The extensive root
systems of trees and shrubs absorb nutrient in large quantities for their
growth. Roots of some plants are able to sequester excess nutrient in their
roots. The anaerobic bacteria inhabits outside the rhizomes of roots are able
to denitrification of excess nitrogen. After conversion of excess nitrate into
nitrogen, it expels into the atmosphere.
Stream of river bank protection again
erosion: The extensive roots system of trees, grasses
create a mat to hold the soil in a place. Roots absorb the water in large
volumes from the bank so it is not allowed water content of the soil in the
bank to reach to saturated level. Thereby it minimizes the risk of bank
collapsing. Leaf litter from the buffer increases the roughness of the bank so
it reduces the river flow velocity. Thereby it minimizes the ability of river
flow to erode the bank.
Provide wildlife habitats: Riparian buffers create the animal
and plant communities with high diverse and productivity. Some animals only
come to the riparian buffer for food, nesting and nursery while other inhabits
as their permanent habitat. Animals use
trees and shrub as their nesting places. Wildflowers provide nectar for humming
birds. Evergreen shrubs and tress serve as a winter cover for wild life. Riparian
acts as the corridors for the wildlife. They support to link the habitats with
same type of some animals. Migrating birds find fruits and insects in the
riparian zones. The buffer zones offer nectar and host plants for certain
butterflies and moths species. Salamanders dig the soil and put their eggs
among the leaf litter in the floor of buffer zones.
Enhance the quality of aquatic
habitats: Riparian
buffers provide fundamental food sources of food webs of aquatic ecosystems.
Leaf litter falls into the water bodies are decomposed by microbes so that
organic matter and nutrients become available for other plants and animals such
as collectors and shredders. Macro invertebrates and small fishes also depend
on this leaf matter. These macro invertebrates and small fishes are eaten by large
fishes. In addition to food, riparian provides shelter for aquatic life.
Shelter and wind blowing from the buffer zone help to lower the temperature and
maintain within a stable range. Thereby it improves the oxygen solubility in
the water. Broken branches provide better hiding places for macro invertebrates
and small fishes to escape form their predators.
Aesthetic and recreational value: In addition to ecological values,
riparian buffers attract the local and foreign tourists due to its fascinating
surrounding. People use the aquatic ecosystem associated with the buffer zone
for swimming, boat riding, walking, fishing and bird watching. The stream or
river and the riparian buffer improve the regional landscape. The tourisms
bring good income and development for the rural communities.
Increase economic value: Landholder can earn good income
when their riparian buffer zones are well managed and maintained. In addition
to protection of aquatic water bodies, the buffer zones provide firewood,
fruits, medicines, tanning and dyes and honey produced by bees. After trees get
mature, they can be cut for the woods, while replacing them by newly planted
trees. They provide winter protection for livestock. They trap water which is
even available under drought conditions for land. It reduces the spread of pest
and diseases attack. Well managed buffer zone can be used for eco-tourism which
gives high income.
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