Restoration Terms

A digger log is a wooden log that is installed in a freshwater stream. This helps to restore and create fish habitat as is cleans and oxygenates the water, as well as produce deep pools and spawning beds. These structures are essential for river restoration as it prevents the extinction of fish species such as Speckled Trout and Atlantic salmon.

Rock sills have the same function as digger logs with the exception that large rocks are used to build the structure as opposed to wooden logs. The advantage of rock sills is that they do not require as much maintenance and repairs as digger logs.

Deflectors are installed to reduce the width of rivers that have been over-widened.

Berms are made of local vegetation (alders 2”or thicker) that is tied together and placed at the start of diversion channels from a river. Silt and leaves collect in the alders, blocking off the side channel. This keeps the water in the main river channel, allowing the water depth to increase and the water temperature to decrease.

The Sackville Rivers Association has been involved in many bank stabilization projects within the Sackville River Watershed. This has involved armour stoning, gabion wall installation, and/or revegetation using various plant species.

Stream order is determined as follows:

 a) The entire watershed for the river in question is mapped out, using a consistent topographical map (e.g., 1:50,000) scale.

 b) First order streams are defined as those segments having no tributaries. First order streams are assigned a value of 1.

 c) Subsequent stream orders are assigned values according to the method established by Strahler (1957, p914), Figure 1.

 d) Where stream segments of the same order come together, the resulting segment is assigned the next highest order. E.g.: where first order streams join, the resulting stream segment is elevated to the second order (2).

e) Where segments of differing orders come together, the resulting segment retains the order of the highest contributing tributary.

f) Where a stream enters a lake, the lake is treated as part of the stream.  If more than one stream enters a lake, the outflow of the lake retains the order of the highest contributing tributary segment (Figure 1). If two streams of the same order run into a lake, the outflow increases to the next stream order.

Trophic Status depends on the amount of nutrients available to enhance plant growth and is a critical measure of lake water quality. The trophic status can be determined by measuring nutrient concentrations (phosphorus and nitrogen), agal densitity and in some lakes, water clarity. 

Lakes with few nutrients and low biological productivity are referred to as “oligotrophic“. Lakes with higher nutrient concentrations and high productivity are referred to as “eutrophic“. Eutrophic lakes are characterised by abundant plant life, including algae, and consequent low water clarity. Lakes with an intermediate productivity are called “mesotrophic” and generally combine the qualities of oligotrophic and eutrophic lakes. Classification of lake trophic status into oligotrophic, mesotrophic or eutrophic provides a simplified framework for lake management and a point of reference for lake managers. There are many means of classifying lake trophic status but all are based on measurements of trophic status indicators such as phosphorus concentration, agal concentration or water clarity and assigning lakes to a category based on the values measured.