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The information from the impairment identification assessments is used to
- Summarize the causes of land use impacts responsible for the impairment.
- Understand the processes affected.
- Identify specific locations and reaches associated with adverse impacts.
- Characterize the time trends of impacts (potential recovery periods).
- Describe the specific nature of impairment (direction, magnitude and trend ofchange).
- Note the consequence of change.
- Support decisions regarding the nature, location, extent and quality of mitigation (implementation).
Once this information is analyzed, the monitoring design can proceed. The next step is to identify a strategy for monitoring. Effectiveness monitoring should always be conducted near the activity or condition responsible for the initial impairment. Four primary design strategies often utilized include
- Measurements obtained before versus after the initiation of a management change in the land use activity, mitigation, restoration, enhancement, etc. This can be very effective as it establishes a pre-calibration period that identifies pre-mitigation variability of the measured parameters. Following mitigation, departure can be readily determined, assuming measurements take into consideration the aforementioned variability factors.
- Measurements or observations taken above versus below impact areas related to specific land uses and specific mitigation. For example if two different grazing strategies are implemented, measurements of effectiveness can be observed above versus below fence line contrasts. This can also be implemented where a mitigation practice may only influence the lower reach of a river compared to the upper reach (assuming the same stream type).
- Measurements obtained determining departure from paired watersheds are often helpful as similar climatic events similarly impact both watersheds. The "pairing" would contrast a watershed that had extensive mitigation or land management change with one had not been changed. This also assumes variability of scale, temporal and spatial variability, and comparisons of similar landscapes and stream types have been identified.
- Measurements obtained for a disturbed reach or site receiving mitigation compared to a reference condition. This type of monitoring can occur at locations far removed from the reference reach. The reference condition however, must be of the same soil type, stream type, valley type, lithology, and vegetative type.
The information supplied in the first list leads the observer to identify the locations, nature of processes affected, extent of the impact, quality of mitigation implementation, etc. For example, if the dominant process impacted by a land use is causing disproportionate sediment supply, land loss, and river instability; and is determined to be accelerated streambank erosion, then the lateral stability monitoring would
- Locate reaches of the same stream type that represent an unstable bank.
- Locate reaches of the same stream type that represent a stable bank.
- Identify permanent cross-sections on each set of reaches.
- Install bank pins (if conditions warrant) and/or toe pins (see monitoring methods).
- Inventory vegetation and bank material, slope etc. for each site (see monitoring methods).
- Resurvey both streambanks at least once peryear to measure soil loss (lateral erosion) and total volume (in cubic feet and tons per year).
- Compare annual lateral erosion rates over time to the stable reach and document rate of recovery based on the nature of the mitigation.
Vertical stability and enlargement rates and direction can also be monitored using permanent cross-sections in a similar stratification procedure (comparison to reference reach, above versus below, before versus after, etc).
Continue Monitoring Section
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