Based on the obtained results, the MB4, MS5 and MI3 models are selected as the best models for simulating scour depth for the ski-jump bucket, sharp-crested weir and inclined slope controlled structure cases, respectively. The MB4 model includes four dimensionless parameters, i.e. ⁠. Table 6 shows the results of the sensitivity analysis of the GEP and FFNN models. According to the table, is the most important parameter affecting the scour depth simulation downstream of the ski-jump bucket, while shows the lowest impact.

Table 6

Sensitivity analyses of the best data driven models

Omitted variable .	Model .	CC .	R2 .	RMSE .	MAE .
Ski-jump bucket (MB4 model)
	GEP	0.318	0.439	0.065	0.052
	FFNN	0.203	0.261	0.189	0.085
	GEP	0.411	0.457	0.064	0.045
	FFNN	0.535	0.581	0.060	0.039
	GEP	0.623	0.694	0.048	0.037
	FFNN	0.741	0.817	0.038	0.029
	GEP	0.598	0.651	0.051	0.036
	FFNN	0.477	0.511	0.081	0.046
Sharp edge overflow (MS5 model)
	GEP	0.224	0.304	0.273	0.159
	FFNN	0.345	0.567	0.207	0.146
	GEP	0.763	0.817	0.150	0.086
	FFNN	0.821	0.852	0.126	0.062
	GEP	0.613	0.709	0.174	0.097
	FFNN	0.736	0.826	0.142	0.074
	GEP	0.588	0.649	0.191	0.111
	FFNN	0.711	0.771	0.163	0.086
	GEP	0.491	0.519	0.219	0.128
	FFNN	0.628	0.679	0.192	0.090
Inclined slope controlled structure (MI3 model)
	GEP	0.411	0.498	0.282	0.246
	FFNN	0.398	0.439	0.187	0.095
	GEP	0.122	0.232	0.338	0.290
	FFNN	0.233	0.394	0.302	0.243
	GEP	0.321	0.413	0.298	0.232
	FFNN	0.285	0.382	0.306	0.237

Omitted variable .	Model .	CC .	R2 .	RMSE .	MAE .
Ski-jump bucket (MB4 model)
	GEP	0.318	0.439	0.065	0.052
	FFNN	0.203	0.261	0.189	0.085
	GEP	0.411	0.457	0.064	0.045
	FFNN	0.535	0.581	0.060	0.039
	GEP	0.623	0.694	0.048	0.037
	FFNN	0.741	0.817	0.038	0.029
	GEP	0.598	0.651	0.051	0.036
	FFNN	0.477	0.511	0.081	0.046
Sharp edge overflow (MS5 model)
	GEP	0.224	0.304	0.273	0.159
	FFNN	0.345	0.567	0.207	0.146
	GEP	0.763	0.817	0.150	0.086
	FFNN	0.821	0.852	0.126	0.062
	GEP	0.613	0.709	0.174	0.097
	FFNN	0.736	0.826	0.142	0.074
	GEP	0.588	0.649	0.191	0.111
	FFNN	0.711	0.771	0.163	0.086
	GEP	0.491	0.519	0.219	0.128
	FFNN	0.628	0.679	0.192	0.090
Inclined slope controlled structure (MI3 model)
	GEP	0.411	0.498	0.282	0.246
	FFNN	0.398	0.439	0.187	0.095
	GEP	0.122	0.232	0.338	0.290
	FFNN	0.233	0.394	0.302	0.243
	GEP	0.321	0.413	0.298	0.232
	FFNN	0.285	0.382	0.306	0.237

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