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<br />.
<br />
<br />756
<br />
<br />HYDRAULIC ENGINlc~RING '94
<br />
<br />tion in 10 min. Ib and 1 day are 30.0mm. 93.Omm and 226.3mm. respectively. The
<br />evaporation amount in the watershed reaches 760mm in a general year.
<br />The watershed is typical both "in soil loss and hydrologic survey. There are 12 pre.
<br />cipitation gauging stations and two evaporation observation points uniformly distrib.
<br />uted on its area. Also, a hydrometric station is built at the outlet oftbe basin.
<br />According to outdoor experimental data. W!II-80mm. Fo-O.47. Fc=3.2S,
<br />k=O.018, D=-O.08mm. CE-2.S. Based on tbe analysis of photo map. C" -0.554. The
<br />processes of flood and sediment discharge in 1990 were simulated. The time interval of
<br />simulation was 6 min. As shown in Fig.2 and Fig.3, a satisfactory calculated result is
<br />obtained.
<br />
<br />Q(mJ/I)
<br />
<br />___""
<br />-- - simulated.
<br />
<br />.
<br />2
<br />.
<br />.
<br />.
<br />"
<br />1>
<br />
<br />.
<br />Umm) 1
<br />__"" .
<br />-- - lIimulatcd
<br />
<br />"
<br />
<br />
<br />1 101 20] 301 401 ,..1 Q)1 701
<br />
<br />200
<br />
<br />"
<br />
<br />100
<br />
<br />,
<br />
<br />.
<br />
<br />Q
<br />" 101 201 301 401 SOl 601 101
<br />TimeO.lh
<br />
<br />Timco.lh
<br />
<br />Fig.2 ne water disch.rac graph in 1990
<br />
<br />Fie.3 The sediment discharge graph in 1990
<br />
<br />Future work
<br />Sediment yield in mountain regions, which is now a ltracling inceasiog concern,
<br />depends on many facton such as cUmale. runoff, etc. The research needs related to the
<br />above work include: parameter values in this article need further rcrmment by experi.
<br />mental studies under various natural conditions; the effect of the basin on sediment
<br />yield; how to cIanify the watershed into different catagories and asseSs quantitatively
<br />the impacts of human actively in mountains on sediment yield.
<br />
<br />Acknowledgements
<br />This work was supported by the Chinese National Foundation of Natural Sci.
<br />ences under Contract No.49371016.
<br />
<br />References
<br />
<br />Simons, D,b., Lit R.M., EngineeriDI Analysis of Fluvial, Simons, Li and AssociSOltes
<br />Inc, 1984,
<br />ZhOD, R.Z.. Hydrologic Simulation of Watershed: Xinganjang Model and Shanbei
<br />Model, The hydro-power preos,l984(in Chin...),
<br />Li. R.M., Shen, H.W., and Simons, B.D., Mechanics of erosion by overland flow,
<br />Proc. ofthe lSth ConJl'esI Inter. Auo. for Hydrology Research. Vol.,I, 1973.
<br />Xie, S.N. and Zhang, R.t Sediment Yield Model for the Middle stream Area of the yel-
<br />low River, The University ofQingbua,1992 (in Chinese).
<br />
<br />1
<br />
<br />.
<br />
<br />.
<br />
<br />Analysis of Levee Design in a Monntain River Using Two-Dimensional
<br />Flow Modeling
<br />Diane M,L, Mas, Student Member ASCE'
<br />Andrew J, Miller', James A. Smith" Wei-hao Chung'
<br />
<br />Ahslract
<br />The South Branch of the Potomac River experienced extreme flooding in
<br />November 1985, A flood wilh an estimated return period of 400 years caused $33
<br />million in damage in Petersburg, West Virginia, Subsequently, a local flood
<br />protection study was conducted by the V,S, Army Corps of Engineers to evaluate
<br />options for flood proteclion (VSACE 1990), A key component of that sludy was
<br />the use of HEC-2 to simulate water surface elevations for a variety of flow
<br />magnitudes under existing and pre-flood conditions.
<br />Three major goals are pursued in this study. The first is to use the two-
<br />dimensional numerical model, RMA2, to simulate water surface elevation and flow
<br />velocity for the 5o-yr, IOO-yr, and 400-yr floods in order to compare tbe resulls of
<br />the two-dimensional model with those previously obtained using the one-
<br />dimensional HEC-2 model. Our purpose is to evaluate what additional infonnation
<br />useful for the design of flood protection plans may be ubtained from the two-
<br />dimensional simulations. The second goal is to examine the effect of proposed
<br />levees on flow during the 5o-yr, 1000yr, and 4OO-yr floods, Finally, an ohjective is
<br />10 examine the interaction between river and flood plain morphology and the
<br />spatial variation in flow during flooding, and in particular, to explore the effect of
<br />alternating expansions and contractions in the width of the flood plain.
<br />Study Area
<br />In Ihc region where Petersburg is located, the shape of the flood plain is
<br />highly correlated wilh geologic setting, The South Branch flows through an
<br />alternating series of wide alluvium covered valley floors and bedrock constrictions
<br />(called gaps), As a result of Ihis particular relationship between geology and flood
<br />plain morphology, the bedrock constrictions create backwater effects which lead to
<br />higher flood crests upstream and also function as nozzles, releasing discharge
<br />
<br />I Graduate Student.3 Assistant Professor. Department of Civil Engineering and Operations
<br />Research, Princeton University, Princeton. NJ 08544
<br />2 Associate Professor. Department of Geography, University of Maryland, Baltimore. MD
<br />11118-5398
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