 |
| Titel |
Towards an extension of the hydraulic geometry concept to include tidal networks |
| VerfasserIn |
Maximiliano Sassi, Ton Hoitink |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057205
|
|
|
|
|
|
| Zusammenfassung |
| Relations between water discharge and the geometric properties of channels are known as
Hydraulic Geometry (HG) relations. HG relations are of fundamental importance to water
management in channel networks, and they are scientifically interesting for their relation
with geomorphological evolution. River delta channels typically scale according to
HG relations such as A=Qp, where A is channel cross-sectional area, Q is water
discharge, and the exponent p is typically in between 0.8 and 1.2. Our aim is to
improve the HG concept to make the equations dimensionally homogeneous and
to include the effects of tides, which are generally ignored in HG theory. Tidal
rivers are intrinsically more complex than rivers free of tidal influences, as tidal
propagation is influenced by river discharge and vice-versa. Systematic variation
of the tidal range may lead to a cyclic variation in water discharge distribution at
bifurcations, affecting HG relations. We present preliminary results from research in
the Mahakam delta channel network in Indonesia, which represents a tide-river
dominated delta that has prograded 60 km over the last 5000 years. Bathymetric
surveys were conducted in the network of nearly rectilinear distributaries connected to
sinuous tidal channels. Based on a geomorphic analysis of the present distributary
network, we show that channel geometry of the fluvial distributary network scales
with bifurcation order. Opposed to the case of river deltas, bifurcation order does
not fully explain bifurcate branch length or bifurcate width ratio. Tidal channels
attached to the fluvial network show convergent widths with intrinsic wavelengths
decreasing landward, and possible signatures of ebb/flood transition in sediment
transport. Our results may help to understand the morphological evolution of delta
channel networks affected by tides, improving idealized models of delta evolution. |
|
|
|
|
|
|