The 10th Int. Conf. on Hydroscience and Engineering (ICHE-2012), Nov. 4 – Nov. 7, Orlando, USA
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HIGH RESOLUTION SIMULATION OF SURFACE WATER FLOW IN
NATURAL CATCHMENT AREAS
Franz Simons1, Jingming Hou2, Ilhan Özgen3 and Reinhard Hinkelmann4
After a heavy rainfall event, surface runoff occurs and small creeks have to transport strongly
increasing discharges resulting in big flooding areas. The overland flow becomes very complex and
is influenced by the micro-relief and local details of the land use. In classical rainfall-runoff models,
the local details of the flow processes, relief and land use are usually neglected. However, these are
very essential for the calculation of infiltration and also evaporation, which play an important role in
the natural water cycle. Further, it is desirable to know the spatial distribution of water depths and
flow velocities for computing discharges and transport processes, e.g. of sediments or contaminants.
Models based on the depth-averaged shallow water equations (SWE) allow high resolution
simulations of the processes mentioned above and provide spatially distributed results. The
exploration methods such as laser scanning have been significantly developed in recent years and
they provide high resolution information about the relief and land use. Consequently, SWE solvers
can be chosen for high resolution runoff simulations in small catchments to investigate their
suitability as an alternative to a classical rainfall-runoff model.
A numerical scheme for solving the two-dimensional depth-averaged shallow water equations
based on the Finite-Volume method (Liang 2010) was implemented in our software HMS (Hydro
Modeling System). Flux computation is carried out with the HLLC approximate Riemann solver
which provides robust solutions for complex flow conditions such as wetting and drying domains,
sharp fronts, hydraulic jumps or complex topographies. High-order accuracy in space is achieved by
a Total Variation Diminishing method. Precipitation and infiltration are considered as source/sink
terms in the mass balance equation. Thereby, the infiltration rate can be computed by either the
Green-Ampt model or Philip’s infiltration equation.
The suitability of our model has already been proven by several comparisons with analytical
solutions and other test cases. As an application for this contribution, a simulation of a rainfall event
in a small alpine catchment which is located in the Vorarlberg Alps (Austria) was carried out.
Detailed information on the study area can be found in Lindenmaier (2008).
In this case study the surface runoff in the sub-catchment area of creek 3 (Fig. 1, left) was
simulated for a rain event in July 2008. In total, a rainfall of ~160mm in ~100h was measured. The
peak discharge at the outlet of the sub-catchment was 0.2m³/s. All simulations were carried out on a
1m² regular mesh with 147 400 cells.
1
Scientific assistant (franz.simons@wahyd.tu-berlin.de)
Scientific assistant (jingming.hou@wahyd.tu-berlin.de)
3
Scientific assistant (ilhan.oezgen@wahyd.tu-berlin.de)
4
Full professor (reinhard.hinkelmann@wahyd.tu-berlin.de)
Chair of Water Resources Management and Modeling of Hydrosystems, Department of Civil Engineering,
Technische Universität Berlin, Germany
2
The 10th Int. Conf. on Hydroscience and Engineering (ICHE-2012), Nov. 4 – Nov. 7, Orlando, USA
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Figure 1 Catchment boundaries and computed discharge for different runoff coefficients.
In our first investigations we considered infiltration by a constant runoff-coefficient and the
influence of the Manning-Strickler friction coefficient and the runoff-coefficient was studied. In
Fig. 1, right the comparison of measured and simulated discharges for two different runoffcoefficients and a Manning-Strickler coefficient of 15 m1/3/s is given. The results only show
qualitative agreement, except the peak discharges for the case ψ = 0.6. The poor agreement can be
explained by the fact, that our current model does not take into account any slower discharge
components in the subsurface like interflow or groundwater flow and exfiltration. Fig. 2 shows the
flow field in the domain at t = 62 h when the strongest discharge was measured for a water depth
bigger than 1 mm. Small creeks with high flow velocities have developed in the domain, while the
flow velocities on the surrounding surfaces are below 0.1 m/s.
Our model is capable to handle complex bottom topographies and complex flow conditions.
To improve the results for runoff simulations in catchments we will add an interflow component to
HMS. This kind of model will then provide a new possibility for transport simulations of tracers or
sediments in catchments.
Figure 2 Simulated flow field at t = 62 h.
REFERENCES
Liang, Q. (2010) “Flood Simulation Using a Well-Balanced Shallow Flow Model”, Journal of
Hydraulic Engineering, ASCE, Vol. 136 No. 9, pp. 669-675.
Lindenmaier, F. (2008), Hydrology of a large unstable hillslope at Ebnit, Vorarlberg: identifying
dominating processes and structures, PhD thesis, Universität Potsdam, Germany.
URL: http://opus.kobv.de/ubp/volltexte/2008/1742/