STEP 5. PLOT OF SPATIAL EXCEEDANCE VS. 
THE CUMULATIVE FREQUENCY 
The CFD is a graphical illustration that summarizes criteria exceedance by plotting 
the temporal and spatial exceedance values listed in Figure VI-6. Temporal 
frequency of exceedance is plotted on the vertical axis and spatial extent of 
exceedance on the horizontal axis (Figure VI-7). The resulting figure can be used to 
draw conclusions about the extent and pattern of criteria exceedance. Each point on 
the curve represents the cumulative amount of space and time in which the criteria 
were exceeded. The potential for observing a spatial extent of exceedance greater 
than the one observed is indicated by the temporal frequency. The curve in Figure 
VI-7 shows two examples of the interpretations of individual points. In addition to 
the interpretation of individual point, the area beneath the curve represents a spatial 
and temporal composite index of criteria exceedance. This area is recommended as 
the basis for defining criteria attainment for all Chesapeake Bay segments and desig¬ 
nated uses. 
co 
CD 
E 
Wm -v,llillfe&il MiMcm &x ’' ?S fen llUl Wsm 
Figure VI-7. The horizontal axis is the spatial extent of criteria exceedance based on monitoring data 
extrapolated using spatial interpolation. The vertical axis is the cumulative frequency of criteria exceedance 
for the monitoring events conducted during the assessment period. 
chapter vi • Recommended implementation Procedures 
