The boundary connectivity index includes the comprehensive stability coefficient C1 and the stream gradient C2, which are the basis to ensure the function of water conveyance and sediment transport, respectively. The stability of the boundary is slightly more important than the continuity of the boundary. Therefore, the weight of the stability coefficient is 0.55, and the stream gradient is 0.45.
The judgment matrix of the flow connectivity index is shown in Table 3. Runoff C3 has the greatest impact on channel connectivity, with a weight of 0.39. The discharge capacity C4 reflects the maximum discharge that the river can transport safely, which is also important for flow connectivity, with a weight of 0.24. The matching index of minimum flow C5 is the ratio of the minimum discharge and ecological discharge; this ratio reflects the ecological function of rivers, and its weight is 0.23. The matching index of maximum flow C6 is calculated by the maximum discharge and discharge capacity. It can reflect not only the longitudinal connectivity but also the lateral connectivity between the floodplain and main channel, with a weight of 0.13.