A. Rinaldo et al., Tidal networks 3. Landscape-forming discharges and studies in empirical geomorphic relationships, WATER RES R, 35(12), 1999, pp. 3919-3929
In this final part of our study [Fagherazzi et al., this issue; Rinaldo et
al., this issue] we propose a simple model for predicting the local peak eb
b and flood discharges throughout a tidal network and use this model to inv
estigate scaling relationships between channel morphology and discharge in
the Venice Lagoon. The model assumes that the peak flows are driven by spri
ng (astronomical) tidal fluctuations (rather than precipitation-induced run
off or seiche, sea surge, or storm-induced tidal currents) and exploits the
procedure presented by Fagherazzi et al. [this issue] for delineating a ti
me-invariant drainage area to any channel cross section. The discharge is e
stimated using the Fagherazzi et al. model to predict water surface topogra
phy, and hence flow directions throughout the channel network and across un
channeled regions, and the assumption of flow continuity. Water surface ele
vation adjustment, not assumed to be instantaneous throughout the network,
is defined by a suitable solution of the flow equations where significant m
orphological information is used and is reduced to depending on just one pa
rameter, the Chezy resistance coefficient. For the Venice Lagoon, peak disc
harges are well predicted by our model. We also document well-defined power
law relationships between channel width and peak discharge, watershed area
, and flow, whereas curved, nonscaling relationships were found for channel
cross-sectional area as a function of peak discharge. Hence our model supp
orts the use of a power law dependency of peak discharge with drainage area
in the Venice Lagoon and provides a simple means to explore aspects of mor
phodynamic adjustments in tidal systems.