Na­ture’s flood con­trol

The News (New Glasgow) - - PICTOU COUNTY - Don Maclean is an out­door writer and bi­ol­o­gist who lives in Pictou County. Don MacLean

The re­cent tragic flood­ing in Hous­ton has shocked peo­ple with both the amount of wa­ter and how fast it ac­cu­mu­lated. While this flood was caused by un­prece­dented amount of rain fall­ing in a short pe­riod of time the fact that nat­u­ral flood con­trol op­tions were lim­ited in this sit­u­a­tion added to the prob­lem.

Like in many ur­ban ar­eas around the world, wet­lands have been filled in, paved over and nat­u­ral brooks and streams di­verted into a pipe or cul­vert.

This con­trasts with nat­u­ral sys­tems where wet­lands serve as an im­por­tant buf­fer dur­ing flood con­di­tions.

Wet­lands come in a va­ri­ety of forms and the Nova Sco­tia Depart­ment of Nat­u­ral Re­sources rec­og­nizes eight types of wet­lands in their land clas­si­fi­ca­tion sys­tem. They are: bog, shrub swamp, wooded swamp, deep marsh, shal­low marsh, mead­ows, sea­sonal flooded flats and open wa­ters. While most of us are fa­mil­iar with swamps and bogs, which tend to re­main wet all the time, sea­sonal wet­lands that may only be wet dur­ing part of the year are also crit­i­cal for wa­ter stor­age and wildlife.

Swamps, and other forms of wet­lands, are an im­por­tant com­po­nent of a healthy aquatic ecosys­tem. Th­ese wet­lands are es­pe­cially im­por­tant habi­tat for frogs, sala­man­ders and toads, par­tic­u­larly be­cause they do not al­low fish, which prey on them, to live there.

In some ar­eas half the pop­u­la­tion of am­phib­ians de­pends on th­ese sea­sonal wet­lands for breed­ing sites and for nurs­ery ar­eas for their off­spring. Th­ese sea­sonal wet­lands, known as ver­nal pools, also pro­vide a place to store wa­ter dur­ing high wa­ter events.

Most of our brooks, rivers and lakes de­pend on a sys­tem of wet­lands to pro­vide them with wa­ter through­out the year. This is in the form of ei­ther sur­face wa­ter or through ground­wa­ter. Ground­wa­ter is es­pe­cially im­por­tant to trout and salmon be­cause it is cooler.

Al­ter­ing wet­lands through hu­man ac­tiv­ity usu­ally re­sults in a neg­a­tive im­pact. Changes in veg­e­ta­tion by re­mov­ing trees and shrubs, paving the ground and drain­ing wet­lands re­duce the amount of rain­fall, snowmelt and runoff the earth can ab­sorb. As a re­sult more wa­ter is forced to run off into brooks and rivers. This in­creased vol­ume dam­ages stream banks, dis­rupt­ing spawn­ing beds for fish and al­ter­ing stream flow pat­terns which pro­motes more flood­ing in the fu­ture.

Th­ese al­tered chan­nels now have in­creased flows in flood con­di­tions and none in the sum­mer. This re­sults in less wa­ter down­stream for lakes and rivers and re­duced wa­ter qual­ity.

Wet­lands are es­pe­cially im­por­tant to fish for their role in wa­ter stor­age and fil­tra­tion. They act as a sponge, soak­ing up flood wa­ter dur­ing the spring, re­leas­ing it slowly through­out the sum­mer. They also help pu­rify wa­ter by nat­u­rally fil­ter­ing wa­ter run­ning off fields, streets and park­ing lots. By trap­ping sed­i­ments and silt they also pro­tect trout and salmon eggs which hatch in the spring and are sus­cep­ti­ble to be­ing smoth­ered by mud and silt.

In the past we have not val­ued wet­lands but there is grow­ing aware­ness of their im­por­tance in the wa­ter cy­cle, es­pe­cially dur­ing flood con­di­tions, and as habi­tat for fish, am­phib­ians and in­sects. All of which com­bine to cre­ate healthy aquatic habi­tat for all of us, and bet­ter trout fish­ing.

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