3.3 Influences of flood waves on HE under CUFV condition
Under CUFV condition, with the increase of T /A , the flood wave became flat and wide (Fig. 2), andq +max, |q |- max, as well as Q max showed decreasing trends with postponed occurrence time (Fig. 6a1, a2, and Table 3).Q max decreased by about 0.138 m2 when T/A increased by 5 (dimensionless). Compared Fig. 5b1 with Fig. 6a1, it could be seen that the change ofq with T /A was similar to that of q withT . The only difference was that the effect of T /Aon q was greater. Q max, however, showed the opposite trend in response to changes in T /A andT (Fig. 5b2 with Fig. 6a2), mainly because the change inT /A was accompanied by a change in A in the opposite direction. According to previous studies (e.g. Liu et al., 2019; Mahmood et al., 2019), the influence weight of A onQ max is significantly greater than that ofT . Thus, when T and A varied by the same amount but in opposite directions, the superposition effects of the two would make the change trend of Q max follow with that ofA . In addition, the change trends of RT andQ max with T /A were opposite, which was different from the same changing behaviors of RT andQ max with the other flood wave parameters. For each increase of 5 (dimensionless) in T /A , RTincreased on average by 0.301 days.t R/t F decreased withT /A , which could be explained by Fig. 6a2, that is,t R and t F increased simultaneously with T /A , but the former increased less than the latter. To demonstrate the differences between conditions of constant upstream flood volume and non-constant upstream flood volume, the results of this study were compared with those from Siergieiev et al. (2015), as shown in Fig. 7. It was found that the change trends ofRT or t R/t F were basically similar (T /A < 50), while the trends of Q max were completely different.