Design floods for all of Canada

Figures & data

Figure 1. Flow chart of method.

Figure 2. Comparison of median annual flood estimated from daily and instantaneous annual maximum flows.

Figure 3. Gauging stations with at least 10 years of suitable flood peak data.

Figure 4. Histogram of record lengths.

Figure 5. QMED plotted against gross catchment area, highlighting catchments with a large difference between effective and gross areas.

Figure 6. Residuals in the QMED regression equation plotted at the centroid of each gauged catchment.

Figure 7. L-moment ratios for all gauging stations in Canada with at least 20 years of flood peak data. Each circle represents a gauging station.

Figure 8. L-CV ratio plotted at the centroid of each gauged catchment.

Figure 9. L-skewness ratio plotted at the centroid of each gauged catchment.

Figure 10. Cross-validation results for annual probability of 1 in 2.

Figure 11. Cross-validation results for annual probability of 1 in 20.

Table 1. Summary of cross-validation results for ungauged catchments.

	Bias (%)	RMSE (log scale)	95% range of ratios	50% range of ratios
	1 in 2 annual probability flood (QMED)
All	−2.7	0.540	0.34–3.25	0.73–1.21
Regulated rivers	0.6	0.609	0.31–4.04	0.75–1.31
Non-regulated rivers	−4.8	0.492	0.37–3.15	0.72–1.18
	1 in 20 annual probability flood
All	−2.2	0.535	0.33–2.96	0.73–1.25
Regulated rivers	3.6	0.585	0.37–3.64	0.77–1.37
Non-regulated rivers	−5.7	0.501	0.31–2.74	0.71–1.20