Surface Water Depth Research Articles

Laboratory experiment, field and remotely sensed data analysis for the assessment of suspended solids concentration and secchi depth of the reservoir surface water

A laboratory experiment was conducted to determine the spectral characteristics of different types of sediment under suspension in water and to select an optimal wavelength for the quantification of suspended sediment concentration and secchi depth (water clarity) in the Tawa reservoir, using the Indian Remote Sensing Satellite-1A Linear Imaging Self Scanning Scanner-I (IRS-1A LISS-I) data. It was noted that the correlation between suspended sediment concentration and reflected radiance varied with colour, mineral composition of sediment and grain size. The clay minerals of low specific gravity had a larger value of reflected radiance than those from high specific gravity non-clay minerals. The laboratory results indicated that an algorithm to quantify suspended sediment concentration and secchi depth in the reservoir can be developed from reflected radiance received by the satellite. For this purpose the Tawa reservoir on the Tawa river of the Narmada basin in Central India was selected. Tawa reservoir water samples were collected on 20 October, 1988 concurrent with an IRS-1A overpass. The secchi depth, pH, and conductivity measurements were made at all the sampling points. The samples were analysed to determine the concentration of total suspended matter, grain size and mineralogy. A positive functional relation exists between the concentration of suspended solids and the visible wavelength bands 1, 2 and 3 (0.45 to 0.68 mu m). On the other hand, the secchi depth of water increases with the decrease in reflected radiance. It has been observed that concentration, mineralogy and grain size of the suspended solids are the main factors which influence the reflected radiance.

Volume Balance Irrigation Advance Equation: Variation of Surface Shape Factor

In application of the volume balance (VB) models, it is generally assumed that the average depth of surface water is constant. This basic assumption may cause significant errors in computing advance. In this paper an accurate algebraic VB equation is developed to predict the advance phase in surface irrigation. In the suggested analysis the average surface water depth is considered to be variable in time. By systematic analysis of accurate kinematic-wave (KW) numerical solutions, the behavior of the surface profile shape factor used in the VB equation is examined. A new equation describing the time dependence of the surface shape factor is derived. Comparison tests indicated that the suggested variable surface shape factor VB equation produces essentially the same results as the KW numerical method. The suggested equation is improved for the case of level or low sloping borders.

Stream Channelization and Changing Vegetation Patterns in the U. S. Coastal Plain

The southeastern U.S. Coastal Plain contains high-density stream networks and the largest area of alluvial wetlands in North America. Among the most common flood-control methods in this region is stream channelization. Its purpose is to increase channel capacity and flow velocity so that water moves more efficiently downstream and thereby reduces flooding. Channelization typically includes deepening and widening the stream channel and shortening it by cutting off meanders. Landowners and those who cultivate in the adjacent floodplains are the primary beneficiaries. In addition to closely involved government agencies, such as the U.S. Army Corps of Engineers and the U.S. Soil Conservation Service, local landowners have been the strongest advocates for channelization. Awareness of the physical and biological problems caused by channelization is growing. Environmental degradation of alluvial habitats has been given serious attention in channelization project planning in recent years. Less destructive channel modifications have been implemented, and some attempts have been made to restore riparian habitats affected by channelization. For example, the Kissimmee River in south Florida, which was channelized in the 1960s, is being restored by reintroducing river flow into remnant channels (Loftin, Toth, and Obeysekera 1990; Shen, Tabios, and Harder 1994). The primary justification is the reestablishment of natural hydrologic conditions and the consequent enhancement of the river's biological resources. A similar restoration project is in the early planning stages for the Obion-Forked Deer River system in western Tennessee, also channelized in the 1960s. The destructive effects of channelization on water quality and aquatic ecosystems are well documented in Brookes's review of 1988. But until recently, little attention has been paid to the effects of channelization on bottomland terrestrial ecosystems. Flood frequency and related physical conditions (including the depth of surface water and the water table, as well as the accumulation of sediment and organic matter) are among the most important factors controlling the presence and distribution of bottomland terrestrial species and are the basis for most classifications of floodplain plant communities (Penfound 1952; Huffman and Forsythe 1981; Wharton and others 1982). Stream channelization significantly alters these conditions in the adjacent bottomlands. But few attempts have been made to link changes in floodplain hydrogeomorphic conditions following stream channelization directly to plant-community composition. Western Tennessee and northwestern Mississippi is an area of the Gulf Coastal Plain in which almost all of the major streams and many of their large and small tributaries have been channelized [ILLUSTRATION FOR FIGURE 1 OMITTED]. These river systems have been studied extensively, and much is known about channel behavior, floodplain hydrology, and bottomland vegetation (Schumm, Harvey, and Watson 1984; Hupp 1987; Simon and Hupp 1987; Simon 1989, 1994; Shankman and Drake 1990; Shankman and Pugh 1992). But the response of forest communities to changing physical conditions is by no means clear. Most floodplain tree species in this region live for decades or centuries, which greatly exceeds the amount of time that has elapsed since extensive channelization began. As a result, short-term observations of bottomland forest are, in all but a few cases, unlikely to reveal forthcoming changes. In this article I examine the potential effects of channelization on bottomland terrestrial habitats in the southeastern United States. Probable changes induced by channelization in forest communities are assessed based on geomorphic processes and life-history characteristics of common bottomland species. In addition, changes in flooding, sedimentation, and restricted-channel migration that follow channelization are evaluated. Changes in natural hydrogeomorphic conditions are directly linked to floodplain habitats and to regeneration of bottomland species. …

The global ocean flux of particulate organic carbon: Areal distribution and magnitude

The magnitude and distribution of the particulate organic carbon (POC) rain rate to the seafloor in the Atlantic, Pacific and Indian Ocean basins between 61°N and 61°S has been estimated from benthic oxygen flux estimates (for water depths ≥ 1000 m only). The calculation utilizes the extensive data sets of sedimentary organic carbon, CaCO3, and accumulation rate to extrapolate between individual benthic flux measurement sites using an empirically‐derived correlation between the seafloor oxygen flux and these parameters. The POC flux through the 1000 m depth horizon was then estimated from published correlations between sediment trap‐determined fluxes and water depth. Total oxygen utilization in the deep ocean is estimated to be 1.2×1014 mol O2 yr−1, a value that agrees well with previous estimates which were based on surface water primary productivity, sediment trap, and depth relationships and with deep water respiration rates estimated from apparant oxygen utilization (AOU)‐14C relationships. On the basis of the derived global ocean flux distribution, it is concluded that (1) dissolved organic carbon (DOC) inputs are not required to account for estimated deep water respiration rates; (2) the majority of the POC input to the deep ocean occurs within 30° of the equator; (3) the proportion of primary production that reaches the deep sea does not vary greatly with latitude; (4) gyre and continental margin regions contribute roughly equally to the deep POC flux with a relatively minor contribution from the equatorial divergence region; (5) of the estimated 7.2×1013 mol C yr−1 of POC that sinks below the 1000 m depth horizon, 45% (3.3×1013 mol C yr−1) reaches the seafloor where it is oxidized; (6) when normalized to basin area, average deep flux rates in the Atlantic and Pacific are similar while highest rates are observed in the Indian Ocean; and (7) the results can be fully reconciled only if the benthic flux of DOC is significantly less than the benthic O2 flux.

The Effects of Substrate Type, Surface Water Depth, and Flow Rate on Manganese Retention in Mesocosm Wetlands

AbstractA wetland mesocosm experiment was conducted to determine the effects on Mn retention of substrate type, surface water depth, and flow rate. The main objective of this experiment was to determine if sustained Mn retention could be accomplished under the specific experimental treatments, to recommend design parameters for the construction of field wetland systems for Mn treatment. Crushed limestone was clearly superior to spent mushroom substrate (SMS) with respect to Mn retention. The presence of a layer of free surface water detracted from Mn treatment, while lower flow rates enhanced Mn treatment. Sustained Mn retention was achieved using crushed limestone as the substrate coupled with an absence of surface free water, when inlet water had a pH of 7.0 and no appreciable Fe. Substrate metal extractions indicated that most of the Mn was retained as oxide‐bound Mn (72%), with most (88%) of the Mn retained at the surface of the wetland. Limestone “wetlands” are therefore recommended in the treatment of Mn in neutral‐pH mine water containing no Fe.

Assessing the performance indices and design parameters of treatment wetlands for H +, Fe, and Mn retention

Using correlations analysis on water quality and wetland design parameters from a set of 35 natural wetlands receiving mine water, treatment efficiency was found to be a better index of Fe and Mn treatment than area-adjusted mass removal. However, area-adjusted mass removal was found to be a better index of performance for pH treatment. Weaknesses of using an area-adjusted measure to evaluate wetland performance for Fe retention included a significant load dependency aspect, strong positive correlations to inlet and outlet Fe concentrations, null correlations with vegetation parameters, and a tendency to rate highly small wetlands receiving high flow rates. H + retention was a better indication of pH treatment than treatment efficiency because of its relationships with inlet H + concentration, Fe treatment efficiency, and H + load. Design parameters enhancing Fe treatment efficiency included broad shapes, non-channelized flow patterns, high plant diversity, a southern exposure, and low Fe loads. Design parameters enhancing Mn treatment efficiency included large areas, non-channelized flow patterns, high vascular plant and bryophyte cover, high plant diversity, and low inlet Fe concentrations. Design parameters favoring pH mitigation included broad shapes, low flow rates, low surface water depths, non-channelized flow patterns, high plant diversity and cover, and low inlet Fe concentrations.

RASTER‐BASED HYDROLOGIC MODELING OF SPATIALLY‐VARIED SURFACE RUNOFF1

ABSTRACT: The proliferation of watershed databases in raster Geographic Information System (GIS) format and the availability of radar‐estimated rainfall data foster rapid developments in raster‐based surface runoff simulations. The two‐dimensional physically‐based rainfall‐runoff model CASC2D simulates spatially‐varied surface runoff while fully utilizing raster GIS and radar‐rainfall data. The model uses the Green and Ampt infiltration method, and the diffusive wave formulation for overland and channel flow routing enables overbank flow storage and routing. CASC2D offers unique color capabilities to display the spatio‐temporal variability of rainfall, cumulative infiltrated depth, and surface water depth as thunderstorms unfold. The model has been calibrated and independently verified to provide accurate simulations of catchment response to moving rainstorms on watersheds with spatially‐varied infiltration. The model can accurately simulate surface runoff from flashfloods caused by intense thunderstorms moving across partial areas of a watershed.

A simple method to quantify sources of settling particles in lakes: Resuspension versus new sedimentation of material from planktonic production

A strong relationship (r > 0.99) between settling particulate inorganic matter (SPIM) and total settling particulate matter (SPM) was observed in 315 samples from sedimentation traps in two Swedish lakes, Lake Erken and Lake Limmaren. This relationship can be used to distinguish between different sources of SPM in pelagic systems when the inflow of allochthonous particulate matter is negligible. It is possible to quantify the proportion of material from planktonic production as well as from sediment resuspension in the flux of settling or suspended particulate matter. Furthermore, fluxes of resuspended organic particles can be quantified and distinguished from fluxes of planktonic organic particles. Although Lake Erken and Lake Limmaren are quite different with respect to trophic level, lake surface area and water depth, the estimated proportion of resuspended particles in sedimentation traps was similar in both lakes. Resuspended particulate matter ranged from 35% of the total settling particulate matter up to 99%, with annual means of 83-94%. Moreover, for both lakes it was estimated that, even in epilimnetic traps, only 2046% (annual means) of the total organic settling particulate matter was from planktonic production, whereas 54-80% (annual means) was from sediment resuspension. This is likely to have important consequences for fluxes of nutrients and contaminants.

Correct Form of Hall Technique for Border Irrigation Advance

The Hall technique for computing stream advance down an irrigated border strip is shown to be inconsistent in the selection of numerical parameters for approximating infiltrated volume. This inconsistency leads to violation of mass conservation and to error in computed advance. By viewing it in dimensionless terms, the behavior of this error is demonstrated over the practical range of variation of border‐irrigation parameters with a Kostiakov infiltration formula and Manning roughness formula. It is shown to vary from insignificant magnitudes under 1% to well over 10%. A correction term to neutralize the inconsistency is presented. An alternate formulation free of the inconsistency and suitable for modern high‐speed computers working with a reasonably large number of significant figures is presented. Errors stemming from the basic physical assumption—constant average depth of surface water—are not addressed.

Marine and terrigenous origin of organic matter in modern sediments of the equatorial East Atlantic: the σ 13C and molecular record

The contributions of marine and terrigenous organic carbon in modern organic sediments from the equatorial East Atlantic was quantified, based on the stable carbon isotope composition standardized for sea surface temperature and water depth. In our binary σ 13C mixing model, the marine end member −26 ∞ is redefined at 23°C and 0 m water depth and the terrigenous end member, independent of SST and water depth, at − 26 ∞. Terrigenous carbon fractions account for more than 60% of total organic carbon (TOC) on the shelf off East Liberia and the Ivory Coast and off Gabon. On the upper slope the land-derived fraction decreases in general to less than 20% of the high TOC concentrations, which can reach 3.5 wt%. The distribution of plant wax n-alkanes (C 27, C 29, C 31) and C:N ratios do not parallel those of land-derived organic carbon, but may be controlled largely by carbon degradation and aeolian/aquatic sorting. The ratio of n-alkanols vs n-alkanes (HPA index) varies with water depth in a nonlinear mode. Since both groups of compounds stem from the same source, plant waxes, it is proposed that the HPA index is controlled mainly by degradation and to a lesser extent by sorting prior to degradation. Enhanced n-alkane concentrations (up to 580 μg/gTOC) in the Gambia Basin and in the central Guinea Basin clearly reflect the influx of aeolian organic matter from northeasterly trades near and below the Inter Tropical Convergence Zone (ITCZ). The particle flux from marine plankton is traced by high concentrations of both dinosterol, long-chain unsaturated methyl and ethyl ketones (C 37-C 39), and alkandiols in marine organic matter. Whereas alkenones, synthetized by prymnesiophyte algae generally, reflect upwelling-related productivity off-shore, dinosterol, synthetized by dinoflagellates, is enriched in near-shore areas of high marine productivity linked to fluvial fertilization. All marine biomarker groups show a surprisingly low concentration below the equatorial high productivity belt.

Settling velocity characteristics of sediment detached from a soil surface by raindrop impact

Summary The aim of the study was to ascertain whether the detachment of sediment from a soil surface by raindrop impact is a selective or aselective process. Relationships between particle size and settling velocity were established. Two contrasting soil types with a mean surface water depth of 5 mm were subjected to simulated rainfall at a rate of 56 mm h−1 in modified splash-cups. Mean drop diameter was 2.24 mm. The two soil types were a cracking clay (black earth or vertisol) and a slightly dispersive sandy clay loam (solonchak or aridisol). For both soil types, sediment that was ejected into the air from drop-impact sites had a selective preference for removing sediment with settling velocities corresponding to fine sand-sized primary particles, and fine to coarse sand-sized aggregates. Investigations of the settling velocity distributions of detached sediments sampled from the surface water before ejection or deposition could occur suggested that, within experimental uncertainties, the impact-detachment process is aselective with respect to sediment size or settling velocity for the drop diameter and water depth investigated.

Composition, abundance and biomass of zooplankton in Orinoco floodplain lakes, Venezuela

Zooplankton samples were collected over a 21-month period in five floodplain lakes of the Orinoco River in order to establish zooplankton species composition, abundance patterns, and biomass and their relationships with the patterns of inundations and lake morphometry. 60 rotifer taxa were identified. This group was generally more abundant than copepods and cladocerans (mean : 73,4 % of total zooplankton). Common and abundant rotifer species included K. americana, K. cochlearis, B. mirus, B. gessneri, P. vulgaris and F. longiseta. Copepods were dominated by nauplii (mean : 73,8 % of total copepod stages). Cladocerans were scarce and dominated by M. minuta, C. cornuta and D. spinulosum. Most frequent and abundant zooplankton species were euplanktonic with a dominance of filter feeders and microphagous detritivores. Mean zooplankton density in all lakes ranged from 340 ind./l to 3 486 ind./l. Biomass ranged from 71,1 µg.l (dw) to 432,8 µg/l. Rotifers accounted for 64,7 % of the total mean zooplankton biomass in three lakes while copepods accounted for 57,8 % of the biomass in two lakes. Both density and biomass were markedly seasonal with highest mean values at low waters. Mean density in the lakes was 100 times higher than in the Orinoco main stem. Lakes with highest variabilities in surface area and water depths showed highest zooplankton densities. The type of connection (direct or indirect) established between the lakes and the major source of the water also seemed important to interpret the productivity of floodplain lakes.

Effects of wadi flood hydrograph characteristics on infiltration

The hydrograph characteristics of ephemeral flood flows determine channel bed infiltration losses and subsequent groundwater recharge. The present numerical study demonstrates that cumulative channel bed infiltration under time-varying surfacewater depth is primarily a function of the infiltration opportunity time and the mean depth of water. The temporal distribution of the surfacewater depth is relatively insignificant. Overall, the infiltration process appears to damp heavily the differences in the stage hydrograph.

Seasonal and spatial microhabitat selection and segregation in young Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in a Norwegian river

Seasonal microhabitat selection by sympatric young Atlantic salmon and brown trout was studied by diving. Both species, especially Atlantic salmon, showed seasonal variation with respect to surface and mean water velocities and depth. This variation is partly attributed to varying water flows and water temperatures. In winter the fish sought shelter in the substratum. A spatial variation in habitat use along the river due to different habitat availabilities was observed. Both species occupied habitats within the ranges of the microhabitat variables, rather than selecting narrow optima. It is hypothesized that the genetic basis allows a certain range to the behavioural response. Microhabitat segregation between the two species was pronounced, with brown trout inhabiting the more slow‐flowing and partly more shallow stream areas. Atlantic salmon tolerated a wider range of water velocities and depths. Habitat suitability curves were produced from both species. It is suggested that habitat suitability curves that are based on observations of fish occupancy of habitat at median or base flow may not be suitable in habitat simulation models, where available habitat is projected at substantially greater water flows.

An improved Lewis-Milne equation for the advance phase of border irrigation

The Lewis-Milne (LM) equation has been widely applied for design of border irrigation systems. This equation is based on the concept of mass conservation while the momentum balance is replaced by the assumption of a constant surface water depth. Although this constant water depth depends on the inflow rate, slope and roughness of the infiltrating surface, no explicit relation has been derived for its estimation. Assuming negligible border slope, the present study theoretically treats the constant depth in the LM equation by utilizing the simple dam-break wave solution along with boundary layer theory. The wave front is analyzed separately from the rest of the advancing water by considering both friction and infiltration effects on the momentum balance. The resulting equations in their general form are too complicated for closed-form solutions. Solutions are therefore given for specialized cases and the mean depth of flow is presented as a function of the initial water depth at the inlet, the surface roughness and the rate of infiltration. The solution is calibrated and tested using experimental data.

Methane emissions from the Florida Everglades: Patterns of variability in a regional wetland ecosystem

Natural wetlands are presumed to be major sources of atmospheric methane, but current estimates of the global wetland emission vary by almost a factor of 20. Estimates of global source strengths are based on extrapolation of in situ flux measurements to large areas occupied by broad classes of wetland environments, and recent efforts at refinement of these estimates have concentrated on improving inventories of the global distribution of major wetland types. An additional potential source of uncertainty which has not been quantified is regional scale variability in emission rates within the major wetland types. We conducted an experiment which examined the spatial variability of methane flux within a large regional wetland system, the Florida Everglades. We also investigated the association of flux variability with relevant surface characteristics such as soil thickness, water depth, soil temperature, and vegetative community distribution. Unit area methane flux to the atmosphere from water‐saturated Everglades environments, measured in situ, varied over more than an order of magnitude (4.2 to 81.9 mg CH4/m2/d), depending on which habitat component of the ecosystem was sampled. Observed physical characteristics of the surface (water and soil depth, soil temperature) were not quantitatively associated with the variability in flux rates. However, the distribution of vegetative community types provided an empirical indicator of flux, permitting an inventory of emissions to be based on mapping of regional vegetation patterns. Use of high‐resolution, orbital remote sensing data helped reduce uncertainty in the emission inventory of the Everglades by directing in situ sampling efforts to important habitat types and by providing a means for calculating area‐weighted mean flux for the system as a whole. The results indicated that spatial variability in flux within a major wetland ecosystem can introduce significant uncertainty in extrapolations to larger areas, even if the extent of the major ecosystem itself is well known. The results also suggested that the response of total ecosystem flux to changing water level is not a linear function of flooded area, but is damped, with regional flux at lowered water levels decreasing proportionally less than flooded area. Both sources of variability can be addressed by the combination of remote sensing and in situ techniques we have employed in the Everglades.

Structure and floristic composition of the Heard Island ?pool complex? community

The stratigraphy, hydrology and vegetation of the Heard Island (sub-Antarctic; 53°05′S, 73°30′E) “pool complex” bogs are described. Spatial variation in processes that might have contributed to their formation are discussed. This community occurs where drainage is impeded. with Callitriche antarctica being the indicator species. Particular attention is paid to the interaction of the vegetation, pools and animals. Surface stratigraphy, peat depth, water depth and vegetation composition were measured along transect lines. Species cover abundance data of 300 quadrats were classified using a two-way indicator species analysis program and ordinated using detrended correspondence analysis. The major factors determining vegetation composition were found to be peat depth, surface topography, and the degree and type of animal disturbance. Similarities between the pool complexes on Heard Island and corresponding bogs in Tasmania, and the northern hemisphere temperate and boreal zones appear to diminish as the density of the animals occupying this habitat increases.

A comparison between modified splash-cup and flume techniques in differentiating between soil loss and detachability as a result of rainfall detachment and deposition

Temporal changes in soil loss rates as a result of rainfall detachment were measured in modified splash-cups (kc) for two contrasting soil types with 5 mm depth of surface water at two constant rainfall rates (56 and 100 mm h-1). Results were compared with those from a flume (kf) for the same rainfall duration, rainfall rates, soil types and water depth. Reasons are given why soil loss rate commonly measured from splash-cups is not a true measure of soil detachment by rainfall when surface water is present. In order to yield the true rate of soil detachment, the measured net rate of soil loss must be augmented by a correction accounting for the rate of deposition. Theory for the net outcome of rainfall detachment and sediment deposition was used to interpret net soil loss data at equilibrium from splash-cups to yield true soil detachment rates (eTc), and compared those from a flume (eTf ). The two soil types were a cracking clay (black earth or Vertisol) and a slightly dispersive sandy clay loam (solonchak or Aridisol). Splash-cup modification allowed the proportion of sediment lost as airsplash (and therefore not deposited within the splash-cup) to be quantified to allow calculation of true soil detachment rates, and hence true soil detachabilities. Under constant rainfall rates and water depth, kc decreased significantly (5% level) with time until an equilibrium detachment rate was reached. This decrease was attributed to the development of a deposited layer on the soil surface, coarser in texture than the original soil. Values of kc were higher for the solonchak than the black earth, and increased with rainfall rate. At equilibrium, eTc and qf were approximately three orders of magnitude greater than kcand kf, illustrating the importance of recognizing the deposition process in determining true rates of soil detachment and soil detachabilities. There was no significant difference (5% level) between kc and kf at equilibrium for the black earth, but values of kc were significantly higher (5% level) than kf for the solonchak. There were no significant differences (5% level) between qc and eTf for both soil types at the low rainfall rate, but eTc were significantly lower than eTf for both the black earth (5% level) and solonchak (0.1% level) at the high rate.

Inflow Seepage Influence on Straight Alluvial Channels

A flume study was conducted to identify and analyze the effects of inflow seepage on flow in straight alluvial open channels. The effect of inflow seepage on energy slope, water surface depth, velocity, sediment transport, scour, bed forms, and resistance to flow was investigated. The results of this investigation indicated that inflow seepage increases localized mean channel velocity, energy slope, and stream power in the zone of inflow. The water surface depth decreased for subcritical flow and remained nearly constant for supercritical flow during inflow conditions. Sediment transport was slightly increased when inflow was introduced in the bed. Inflow seepage did not appear to enhance channel scour. Inflow seepage significantly enhanced bed form transformation and the bed roughness. Inflow seepage also caused dunes to become longer, flatter, and move more erratically in the reach where inflow occurred. It was concluded that inflow seepage could significantly influence the channel hydraulics, stream po...

Planform Effects on Tidal Flushing of Marinas

Effects of various geometry parameters on tidal flushing and internal circulation in small‐boat basins (marinas) of rectangular planform were determined in physical hydraulic models by means of a photographic technique incorporating the use of a photodensitometer. The schematic model marinas tested were scaled to have surface areas, water depths, and tide ranges comparable to “prototype” marinas in the Pacific Northwest: Results are presented in terms of spatial average tidal flushing (exchange) coefficients for each configuration tested, and by contour drawings of equal local per‐cycle exchange coefficients for a number of configurations, all at the same tide range. Emphasis is placed on planform geometry and aspect ratio, those variables over which designers may have most latitude in designing a marina for a specific site. Effects of basin length to width ratio are delineated for basins with typical single asymmetric entrances.