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Nova Scotia Wet Places - Floodplains

Eastern Habitat Joint Venture

Each spring and fall, surging rivers and streams overflow their banks and carry nutrient-filled, silt-ladened water over level, open areas known as floodplains. Floodplains help maintain water levels of streams and rivers, and reduce erosion of banks. Flood waters eventually withdraw from floodplains, revealing moist fertile ground. By summer these areas are matted with grasses, and a diverse community of animals has colonised the invitingly lush vegetation. But floodplains are harsh providers. Many animals and plants simply cannot tolerate seasonal flooding; those that can overcome the adversities reap the benefits of the rich floodplains.

Description
Floodplains are nutrient-rich wetlands that form on banks of rivers and streams that seasonally flood. In summer, they appear mainly as grassland meadows that sometimes are interspersed with marshy areas. Some floodplains also may contain shrubs and trees.


Tall meadow-rue


Flood waters deposit fine soil particles on floodplains, thus ensuring this habitat is full of nutrients. By the start of growing season, flood waters subside, exposing rich soils. In many ways, floodplains provide ideal conditions for plant growth.


In Nova Scotia there are two types of floodplain: meadows and seasonally flooded flats.

Meadows form along small streams in woodland and on low lying agricultural land. They are characterised by dense stands of grasses, including blue-joint grass and woolly scirpus. Rushes, sedges and broad leafed plants, such as meadow rue, may also be present.


Seasonally flooded flats often form at points where large rivers slow down as they enter lakes. This kind of floodplain is much larger than the meadow because it experiences more intense flooding. Overall, vegetation is similar to meadows, with tall grasses, like blue-joint, being dominant. However, because of their large size and varied topography, seasonally flooded flats support more diverse plant life than do meadows. Trees, shrubs, ferns and marsh plants, such as cattail, may also be present.


Wildlife of floodplains
Floodplains attract all sorts of wildlife. The combination of rich soil, adequate moisture and lush vegetation provides ideal conditions for a wide variety of animals and plants.


Floodplains are abuzz with dragonflies, mosquitoes, and ground insects, like beetles. The flat expanse of a floodplain enables aerial hunters like the hoary bat, saw-whet owl and northern harrier to readily spot and capture prey. Waterfowl often take advantage of the plentiful cover and forage available in floodplains. Nesting marsh birds, such as least bittern and red-winged blackbird, use floodplains as do many mammals, including muskrat, beaver, otter, shrews, meadow voles and white tail deer.




Meadow vole


Floodplains are both a luxurious and harsh habitat for plants. Though the soil of floodplains are amongst the richest, severe physical disturbance caused by flooding and scouring by ice prevent many plant species from establishing in floodplains. However, some plants do thrive in these conditions. In fact, several species have specialised to live in floodplains, including rare species such as dog's tooth violet and nodding trillium.


Floodplains and the environment

One of the biggest threats to rivers, streams and lakes is siltation, the blanketing of the bottom with fine silt (soil) particles. Excessive siltation destroys habitat of many species of wildlife - most noticeably fish - by making it difficult to breath, much in the same way smoke interferes with our breathing.


Floodplains are one of nature's main defenders against siltation. During times of flooding, floodplains remove silt from water bodies by serving as settling areas for this potentially damaging material. Floodplains also absorb and slow down flood waters, thereby reducing soil erosion downstream and further limiting damage by siltation. Lots of wildlife breath easier because of floodplains.


Conservation

Since settlers arrived, lush meadowlands have served as pasture land or as sources of hay. In some instances, floodplains have been ditched to exploit their rich soil for agricultural use. As society grows, human activities such as agriculture, land developing, recreation and tree harvesting have steadily increased. Today, floodplains face more threats than ever before.



   Helping floodplains...  
  • conserve the natural vegetation growing along the sides of watercourses
  • do not interfere with the natural flowage of rivers
  • limit activities on areas of floodplain
  • use agricultural practices that conserve soil, water and vegetation.
  • install proper river crossings for livestock, people and machinery

Any activity that alters a river's flow pattern potentially endangers its floodplains. For instance, damming, timber harvesting and developing directly on river fronts threaten the health of floodplains. Similarly, direct disturbance to floodplains, through overgrazing, trampling and the use of motorised vehicles, can damage plant communities and destroy a floodplain's delicate soil structure. Floodplains are used and enjoyed by people, but they are not exclusively ours; all of nature depends on floodplains. However, it is solely our responsibility to care for floodplains so that this habitat can continue nature's work.


Leapord frogs