Skip to main content

Watershed Hydrology: Geomorphological Instantaneous Unit Hydrograph (GIUH) Theory

 The Geomorphological Instantaneous Unit Hydrograph (GIUH) links catchment runoff response to quantitative stream network geometry without requiring direct streamflow records. Based on Horton’s Laws of Drainage Network Composition, three morphological ratios are derived:

​Bifurcation Ratio: $R_b = \frac{N_\omega}{N_{\omega+1}}$

​Length Ratio:  $R_l = \frac{\bar{L}_{\omega+1}}{\bar{L}_\omega}$

​Area Ratio: $R_a = \frac{\bar{A}_{\omega+1}}{\bar{A}_\omega}$

​Where $N_\omega,$ $\bar{L}_\omega,$ and $\bar{A}_\omega$ represent stream count, mean length, and mean area of order $\omega.$ Rodríguez-Iturbe’s GIUH formulation computes the peak discharge $(q_p)$ and time-to-peak $(t_p)$ of the unit hydrograph as:

$q_p = \frac{1.31}{L_\Omega} \cdot R_a^{0.43} \cdot v \quad$ 

$\text{and}$ 

$\quad t_p = \frac{0.58 \cdot L_\Omega}{v} \cdot \left(\frac{R_b}{R_a}\right)^{0.55} \cdot R_l^{-0.38}$

​Where $L_\Omega$ is the length of the highest-order stream $(\text{km})$ and $v$ is peak flow velocity $(\text{m/s}).$

​In rugged, ungauged Himalayan sub-catchments, classical rainfall-runoff data collection is physically unfeasible.

​Central water research teams employ high-resolution Digital Elevation Models (DEMs) derived from Indian remote sensing satellites (Cartosat) to automatically extract Horton ratios. Inputting these spatial parameters into GIS-based GIUH solvers yields accurate flood peak hydrographs for regional bridge and culvert designs.

​Note: This technical content was curated and structured with AI assistance to support technical education.

Labels:

Comments

Post a Comment

Popular posts from this blog

RIVER INTAKE STRUCTURE

  RIVER INTAKE As we know intake should be located at the upstream side of the city so pollution is minimum and this river intake should be sufficiently inside the river water so need of water can be supplied at every seasons of the year. Some river intakes are constructed near the bank of river when sufficient depth is available, some are created away from the bank of river when river bed is soft or unstable near bank, sometimes water level raised by constructing weir on the river and sometimes channel created and water led to the intake tower. This all situations divides river intake into two major types: (1) Single well type intake and (2) Twin well type intake. Parts of river intake are Intake well, Intake pipe and Jack well. River intake well has two parts, lower part is Jack well and upper part is surves pump house. SINGLE WELL TYPE RIVER INTAKE In single well type intakes water is directly enter into jack well through the penstockes (openings) created at different level. As ...
Post a Comment
Read more

CANAL INTAKE STRUCTURE

  CANAL INTAKE Canal intake structure An irrigation canal used as the source of water when other source are far from the city. Intake structure constructed near the bank of canal. An intake chamber created inside the canal using concrete or masonry having one bell mouth entry pipe inside it. Intake chamber has opening guarded with coarse screen and bell mouth entry protected with fine screen or mesh. Bell mouth entry located at expected low water level of the canal. Water enters from this bell mouth entry and conveyed through withdrawal conduits to sump well or city.
Post a Comment
Read more

RESERVOIR INTAKE STRUCTURE

  RESERVOIR INTAKE All rivers has not sufficient depth of flow throughout the year and hence dam constructed across the river to form a reservoir having sufficient depth for intake. This intake structure built upstream side near the dam and it is similar to the river intake. A typical reservoir intake well consists number of water entry ports located at various elevations so that relatively clear top water is only drawn at all seasons. All control on this entry ports is at topnof the well. Dry intakes and wet intakes formed according to the position of entry valves outer and inner of the well respectively.
Post a Comment
Read more