Each RUN is the SFWMM output for a particular alternative or scenario. For example, the Starting Point, Alternative 1, the 1995 Base, and the 2050 Base, are all runs.
A performance measure SET is the group of model simulation runs that are compared. For example, a set may compare Alternative 1 with the NSM and the 1995 Base run. Another set could compare Alternative 1, Alternative 2, the 1995 base run and the 2050 base run.
To view the performance measures a particular SET of performance measures must be selected.
In viewing maps, the maps relate to each individual RUN, but are arranged by topic, e.g. hydroperiod distribution, ponding, etc. Maps from different runs (or the same run) can be compared using the side by side map viewer. Similarly maps that relate to different parameters or even input parameters can be compared (e.g. ponding vs hydroperiod or hydroperiod vs land cover).
Different types of performance measures are displayed for each geographical region. In some cases the type of measure is specific to that particular region while in many cases it is common to all the regions. The more common types of performance measures are described here, whereas descriptions of measures unique to a region are described with the performance measure for the region.
Stage hydrographs
Stage hydrographs represent the time series of stage at a particular location (typically average values over a 2x2 mile grid cell). Stage hydrographs can be used to compare pre-drainage hydrograph characteristics with those of different alternatives at the specific location, providing information on how well each alternative performs with regard to seasonal water level fluctuations, minimum and maximum levels and the occurance and frequency of the cell dry out.
Stage duration curves
Stage duration curves provide an indication of the cumulative probability that a particular stage is exceeded or not exceeded. Stage duration curves are produced at the same locations as the stage hydrographs. From the duration curve the probability of exceeding a given stage is easily quantified for each alternative.
Normalized stage hydrographs and normalized stage duration curves are used to reference stage with respect to land elevation rather than NGVD to facilitate comparison of ponding depths. This is important in comparing stages from different alternatives with the NSM values where land subsidence has occurred.
Mean monthly stages
Mean monthly stages at particular locations (cells) permit the comparison of inter-seasonal variability in stage between various alternatives. Mean monthly stages can be long term (period of record) or for chosed periods, e.g. several wet or several dry years.
Hydroperiod distributions, matches and improvement
Cell by cell maps and areal histogram measures of hydroperiod distributions, hydroperiod differences and hydroperiod improvement, were developed to determine how well pre-drainage spatial inundation patterns are reproduced by each alternative. Cell by cell comparisons determine how alternatives compare to, or match, targets at each modeled grid cell and indicate where changes have taken place. Cell by cell comparisons are discussed in more detail in the View Maps section. Areal hydroperiod histograms measure improvement toward desired conditions over an area or for a particular landscape.
Hydroperiod distribution histograms indicate the total area inundated for 30 day inundation period classes, for each of the alternatives compared.
Hydroperiod matches histograms quantify the area that matches the inundation pattern of the target (e.g. NSM) for each alternative. Inundation patterns within plus or minus 30 days of those of the target are considered to match the target. Histogram classes quantify the areas that have either longer or shorter inundation periods than the target.
Hydroperiod improvement histograms quantify the inundated acreage that either improves towards, gets worse than, or overshoots the target (e.g. NSM), relative to a base case or another alternative. "Improvement" implies that the mean annual hydroperiod resulting from the alternative is "moving in the right direction". For example if the hydroperiod of the alternative is longer than that of the base to which it is compared, and is getting closer to that of the target, the hydroperiod of the alternative is said to improve. "Worse" means that the hydroperiod resulting from the alternative is "moving in the wrong direction", e.g. if the hydroperiod of the alternative is shorter than that of the base simulation, and is getting farther from the target, then the hydroperiod is said to get worse. "Overshoots" means that the hydroperiod resulting from the alternative moves toward the target, but goes past it.
Ponding
Ponding histograms quantify the acreage that matches ponding depth targets within each ponding class and for each alternative. Average ponding depths within plus or minus 0.5 ft of the target are considered to match it.
Ponding distribution maps can also be viewed in the View Maps section.
Water Budget
The water budget performance measure presents graphically the volume of water that comes into (positive) or leaves (negative) each particular area. Each term of the water budget is shown for each alternative. Water budget terms inlude rainfall, evapotranspiration, surface flows, groundwater flows, structure flows, pumping, and changes in storage. A residual term is also shown to verify conservation of mass and the accounting.