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We analyse the nonlinear behaviour of an array of curved surge-type wave energy converters(WECs) in a semi-infinite channel of constant depth. Surge-type WECs have attractedinterests by researchers and industry, mainly because of their capability to absorb energy withpotentially large efficiency when excited by incident waves. The vast majority of the theoretical models developed so far on the dynamics of this kindof devices neglect nonlinear contributions. This can be unjustified when nonlinearresonances of trapped modes occur. Indeed, Michele et al. (2018b) recently showed thatsubharmonic resonance and mode competition of trapped modes can increase energyproduction of a system of surging WECs. Moreover, recent investigations on curvedflap-type gates suggest that using curved structures could further improve wave energyextraction efficiency. Motivated by these new aspects, in this work we investigate theeffect of gate surface curvature on the nonlinear dynamics of an array of surge-typeWECs. We show that a small horizontal deviation of the gate surface produces significantchanges in the dynamical behaviour of the system. Using perturbation-harmonic expansionup to the third order, we decompose the nonlinear governing equations in a sequence oflinearised boundary-value problems of order n and harmonic m. The gate shape effectsresonate the first harmonic at the second order, so that three timing with two slow time scalesis necessary. First, we consider the synchronous excitation of a single trapped mode. Products betweenthe gate shape function and the second-order terms force the first harmonic at the third order.We point out that this particular excitation is not possible for flat gates, because in that casethe corresponding evolution equation would be damped and unforced. We also show theoccurrence of new terms in the Ginzburg-Landau evolution equation, which are notpresent in the case of flat gates. We show that nonlinear synchronous resonance ofcurved WECs yields constructive interactions that can be significant for designpurposes. Finally, we analyse the occurrence of subharmonic nonlinear resonance bymonochromatic incident waves. Perturbation expansion of the unknowns leads to anevolution equation similar to that obtained for the synchronous case. Then we define anoptimized PTO coefficient which maximises power extraction under subharmonic resonance.The capture factor reaches much larger values than the theoretical maximum of aWEC in a channel described by the linearised theory. Furthermore, we show thatsubharmonic resonance is associated with increased efficiency of wave power extraction,though the effects of curvature are not always beneficial as we initially thought. [ABSTRACT FROM AUTHOR]