Browsing by Author "Larson, Curtis L."

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Effects of Drainage Projects on Surface Runoff from Small Depressional Watersheds in the North Central Region
(Water Resources Research Center, University of Minnesota, 1979-01) Moore, Ian D.; Larson, Curtis L.
Surface runoff from small watersheds characterized by numerous depressions was studied statistically and by use of a special purpose watershed model. The statistical analyses illustrated the possible magnitude of the storage effect exhibited by lakes, marshes and other depressions. Because of data limitations statistical techniques could not be used to examine the effects on flood runoff of draining these same areas. The model, described in the Bulletin, represents the process of snowmelt, infiltration, soil moisture storage, evapotranspiration, subsurface and surface runoff for four different land drainage conditions, with or without channel development. Application of the model to two small watersheds in Jackson County, Minnesota indicated that drainage development increases annual runoff, storm runoff and peak discharge. The physical characteristics of the main water course in the watershed was the major factor influencing peak discharge at the watershed outlet. Examination of annual flood flows on the Minnesota River at Mankato suggests that downstream effects of drainage development on large watersheds are much less than indicated by this study on small watersheds. Downstream effects and flooding within a watershed are discussed in general terms in the Bulletin.
Hydraulics of Flow in Culverts
(St. Anthony Falls Laboratory, 1948-10) Larson, Curtis L.; Morris, Henry M.
With modern tendencies and developments in highway design, construction of culverts for cross drainage of storm runoff represents n ever-increasing item of expense. As wider highways have been built, culvert lengths have been correspondingly increased. In addition to increased lane width requirements, multiple-lane super-highways are becoming more and more prevalent. Furthermore, allowable curvatures and grades have been reduced, both of which tend to increase culvert lengths by increasing fill heights. For every increase of one foot in fill height, culverts are lengthened several feet.
Investigation of Flow Through Standard and Experimental Grate Inlets for Street Gutters
(St. Anthony Falls Laboratory, 1947-10) Larson, Curtis L.
This report presents the results of an investigation of the flow of water and entrained debris through standard and experimental gutter inlets of the grate type. The investigation was requested by the Minnesota Highway Department in connection with the proposed construction of a length of highway at 6 per cent grade. Under the sponsorship of the Highway Department, the experiments were conducted at the St. Anthony Falls Hydraulic Laboratory of the University of Minnesota.
Methods for Routing Hydrographs Through Open Channels
(Water Resources Research Center, University of Minnesota, 1972-06) Larson, Curtis L.; Rice, Charles E.
In this study a simulation model of an open channel system was used to evaluate some existing flood routing methods, observe the effect of different physical variables on flood wave movement, and to develop a simple routing method. The physical, geometric, and hydraulic components of the model were patterned after real-life conditions common to southeastern Minnesota. The dynamic equations of unsteady flow were used to route flood hydrographs through the channel system and outflow hydrographs were generated to achieve the objectives listed above. The method of characteristics with a specified time interval was used to solve the unsteady flow equations. Two simple storage routing methods, the Method A and the Method B were developed and evaluated. Other simple routing methods evaluated include: the Muskingum, the Puls, and the Kinematic Wave. Complete methods evaluated were the Direct and the Explicit. The methods were evaluated by comparing the results by the methods with the generated results. Comparisons were made on the accuracy of the predicted results, the complexity of the method, and the computation time required for a solution. The work reported herein was carried out in partial fulfillment of the requirements for the degree of Doctor of Philosophy, granted to Charles Edward Rice by the University of Minnesota, June 1972.
Modeling Direct Recharge of Surficial Aquifers
(Water Resources Research Center, University of Minnesota, 1983-04) Knoch, Brian C.; Larson, Curtis L.; Slack, Donald C.
A one-dimensional, physically-based computer model was developed for predicting direct groundwater recharge. The model was verified using three years of data from an instrumented site in east central Minnesota. Although the processes of infiltration and redistribution during frozen soil periods were not modeled, the model is capable of operating during both frozen and non-frozen soil periods. The model includes submodels for evapotranspiration, soil water extraction, snowmelt, surface depressional storage, infiltration and redistribution. The model predicts water table level and soil moisture. Water extraction may also be modeled. The model predicted both water table levels and soil moisture with reasonable accuracy over the the three year period modeled.
Modeling the Infiltration Component of the Rainfall-Runoff Process
(Water Resources Research Center, University of Minnesota, 1971-09) Larson, Curtis L.; Mein, Russell G.
Numerical Routing of Flood Hydrographs through Open Channel Junctions
(Water Resources Research Center, University of Minnesota, 1971-08) Bowers, C. Edward; Larson, Curtis L.; Wei, Tsong C.
The study was concerned with numerical routing of flood hydrographs through open channel junctions. An open channel junction with a main channel above and below plus a branch channel were constructed in the laboratory. All channels were rectangular in shape, but varied in size. Facilities and procedures for supplying hvdrographs to the two channels above the junction were developed. Provision was made for measuring both inflow and outflow hydrographs and also flow depths at selected points in the three channels. A total of 14 experiments were conducted with various combinations of input hydrographs in terms of magnitude and relative timing. Unsteady flow conditions (depth, velocity and discharge) in the three channels were calculated at calculated at 5-ft. length increments and 1-sec. time increments, using the method of explicit finite differences applied to the characteristic equations. A procedure for calculating unsteady flow backwater effects in either or both of the upstream channels was developed and utilized as an integral part of the routing method. The junction routing procedure appears to be fairly general, having been applied in a situation where the channels above and below the junction are at different size, slope and elevation. In particular, it was shown that unsteady flow backwater effects can be represented in the method of explicit finite differences applied to the characteristic equations. Some error can be expected in any numerical method, as well as in all measurements. Due to the measurement error cited above, the amount of error attributable to the routing method cannot be determined. It appears to be on the order of 6 percent, but could be less than this amount.
Predicting Infiltration and Micro-Relief Surface Storage for Cultivated Soils
(Water Resources Research Center, University of Minnesota, 1980-06) Moore, Ian D.; Larson, Curtis L.; Slack, Donald C.
Predicting Peak Flow of Small Watersheds by use of Channel Characteristics
(Water Resources Research Center, University of Minnesota, 1972-06) Gronwald, Ronald F.; Larson, Curtis L.; Pennell, Alfred G.
In previous studies, a method was developed for predicting the effects of channel characteristics, including watershed size and shape on peak flow from small watersheds. The method was incomplete, however, since it lacked a working method of estimating the time parameter for ungaged watersheds. Therefore, the first objective of this study was to satisfy this need. The second objective was to test the overall method as a means of predicting peak flow for small ungaged watersheds, given the runoff volume. The overall method begins with a hydrologic analysis of numerous rainfall-runoff events observed at selected experimental watersheds. This yields certain hydrologic parameters which can be evaluated only for gaged watersheds. Then, the physical characteristics of these watersheds, primarily the channel characteristics, are utilized to evaluate the same parameters by use of an hydraulic or flow approach. If this can be accomplished successfully, the same procedure can be applied to ungaged watersheds. The following conclusions can be made based on the results of the study: A new time parameter, time to 50% of equilibrium, T50, was proposed. It can be evaluated hydrologically, i.e. from observed hydrographs in many but not all cases this is essential if it is to be used in peak flow predictions for other, ungaged watersheds. T50 increases with watershed size, approximately as watershed area to the 1/3 power. It decreases as the mean rate of rainfall excess (qs), increases, varying as qs to the minus ½ power (roughly). The residual variability is substantial, indicating that other factors also affect T50 significantly. The channel characteristics, cross-sectional area and wetted perimeter can be estimated with reasonable accuracy from measurements of bankfull topwidth and depth. However, a number of complete channel cross-sections must be taken or be available in the region in order to evaluate the two coefficients needed, one for area and one for wetted perimeter. It appears likely that these coefficients can be generalized through further study, and also that relationships will have other applications in watershed engineering. Three methods used to divide the watershed into an upper and lower half hyrdologically gave only slightly different results, and therefore, the simplest method (arc) appears preferable. The travel time approach to evaluating the time parameter yields values (designated Tch) that are consistently and significantly lower than the true values (T50). Thus a coefficient applicable to the region is necessary to related T50 to TCH. The peak flow predictions by the methods of this study were quite variable, as compared to the observed values, but on the average were about the right magnitude., i.e. neither consistently high or consistently low. The combination of peak flow equation, the time parameter, T50, and the relationship of Cp, the peak flow coefficient, to the ration D/T50, where D is the duration of rainfall excess, appears to provide a satisfactory but not highly accurate procedure for estimating peak runoff, given the volume of rainfall excess and its approximate time distribution.

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Browsing by Author "Larson, Curtis L."