Catchment Geomorphology and Routing
Catchment geomorphology characterizes the form of drainage basins and networks, and flow routing describes how flood waves move and attenuate through channels and reservoirs.
Definition
Catchment geomorphology is the quantitative study of the shape, relief, and drainage network of a basin; flow routing is the computation of how a flood hydrograph changes in magnitude and timing as it travels through a channel reach or reservoir.
Scope
This topic covers the quantitative description of drainage networks and basin morphometry, their influence on hydrological response, and the hydrologic and hydraulic routing of flood waves through channels and storage. It links the physical structure of catchments to the timing and shape of their runoff.
Core questions
- How are drainage networks and basins quantitatively described?
- How does basin form influence hydrological response?
- How do flood waves attenuate and lag as they move downstream?
- How are hydrologic and hydraulic routing methods applied?
Key concepts
- Stream ordering and bifurcation ratio
- Drainage density
- Basin morphometry and relief
- Time of concentration
- Hydrologic routing (Muskingum)
- Hydraulic routing (Saint-Venant)
Key theories
- Quantitative drainage morphometry
- Horton, later refined by Strahler, established laws of stream ordering, bifurcation, and drainage density that quantify network structure and link basin form to erosional and hydrological behavior.
- Geomorphologic instantaneous unit hydrograph
- Rodriguez-Iturbe and Valdes derived the catchment's response function from the geomorphologic structure of its drainage network, connecting basin form directly to the hydrograph and aiding prediction in ungauged basins.
- Flood routing
- Hydrologic routing methods (such as Muskingum) and hydraulic routing based on the Saint-Venant equations compute the downstream translation and attenuation of flood waves through channels and reservoirs.
Clinical relevance
Drainage morphometry and routing are used to estimate the timing and peak of floods, design and operate channels and reservoirs for flood control, transfer hydrological information to ungauged basins, and provide the channel-routing components of distributed hydrological models.
History
Horton's 1945 laws launched quantitative drainage-basin morphometry, extended by Strahler and others; flood-routing methods developed in parallel through the 20th century, and the geomorphologic instantaneous unit hydrograph of 1979 fused network structure with hydrological response.
Key figures
- Robert E. Horton
- Arthur N. Strahler
- Ignacio Rodriguez-Iturbe
Related topics
Seminal works
- horton1945
- rodriguez1979
- chow1988
Frequently asked questions
- What is stream order?
- Stream order is a numbering of channels in a drainage network by their position in the hierarchy: the smallest unbranched streams are first order, and order increases where streams of equal order join, providing a measure of network size and structure.
- What does flow routing compute?
- Routing computes how a flood hydrograph changes as it moves through a river reach or reservoir, typically lagging in time and lowering and broadening its peak as the wave is delayed and stored, which is essential for downstream flood forecasting and reservoir operation.