BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

8.14.2 ADDITIONAL CONSIDERATIONS FOR MONITORINGIf the checklist objectives call for scientifically and legally defensibleconclusions, data should be quantitative and the hypotheses concerning changeshould be statistically tested. Since quantitative data sufficient for application ofstatistical tests are often expensive to obtain, well-defined objectives and thecareful selection of measurement parameters are vital. Scoping is a critical partto this important process; scoping includes defining checklist objectives,delineating the boundary of the checklist area, and selecting the appropriateaquatic species for evaluation. The selection of species can be based onecological importance, importance for human use (e.g., sport or commercialfishing), or other factors, including legal protection status. 88Frequency of sampling will depend on the original objectives of themonitoring program, the availability of resources, and the size of the projectarea. Seasonal fluctuations of physical and biological parameters may be or maynot be known; therefore, seasonal sampling may be required. A samplingfrequency of once per year may be sufficient for an annual maintenanceproject, unless there is a reason to believe otherwise. 89Experimental design and sampling plans for a specific project area will dependon the nature and magnitude of the project, the use and purpose of the data,and the metrics to be evaluated. The fauna present may be sessile or motilewith populations that vary seasonally and distributions that are random orclustered. In most cases, quantitative studies of the backshore and foreshorebeach and nearshore substrate must also concentrate on the benthiccommunity and any populations of aquatic invasive species. 90Statistical analysis must be used to summarize or describe complex data.Statistics can also be used as a formal decision-making tool to decide whethermeasured temporal or spatial differences between samples are real or whetherthey may be the result of a sampling variability. Commercially available datamanagement systems have options for computing and displaying several typesof statistics. Large amounts of data can be summarized by calculating statisticssuch as measures of central tendency (mean, median, and mode) and dispersion(standard deviation and range).Statistics can also be used to compare sets of data to determine if differencesexist among them and, if so, whether the differences are significant. Statisticalrelationships among variables may be explored using correlation and regressionanalyses. For example, the relationship between the density of a certain benthicspecies and certain physical (water depth, temperature, sediment grain size,88USACE, 1989, EM 1110-2 -5025, Environmental Engineering for Coastal Shore Protection andUSACE, 2008, Coastal Engineering Manual - Parts I-689USACE, 1989, EM 1110-2 -5025, Environmental Engineering for Coastal Shore Protection90USACE, 1989, EM 1110-2 -5025, Environmental Engineering for Coastal Shore Protection andUSACE, 2008, Coastal Engineering Manual - Parts I-6TRPA BMP HandbookCHAPTER 8: Shorezone Protective Structures and BMPs2012 Page 8-89