A FAST RECURSIVE GIS ALGORITHM FOR COMPUTING STRAHLER STREAM ORDER IN BRAIDED AND NONBRAIDED NETWORKS1

ABSTRACT: Stream ordering is a useful property of every river network, having a wide range of applications. A method for determining stream orders that quickly and easily addresses various network topologies and magnitudes is therefore needed. This paper introduces a general recursive stream ordering framework for vector hydrography. It also presents a linear, O(n), stream ordering procedure for braided river networks, which is a major improvement to the existing quadratic, O(n²), procedure. The discussion includes results and interpretations, and the appendices present procedure pseudocodes and thorough line by line explanations.     

塑料排水技术及其在环境岩土工程中的应用

介绍了常用塑料排水材料及其技术要求和性能;阐述了目前国内塑料排水技术在环境岩土工程中的应用状况,并就应用塑料排水技术解决岩土工程中的安全、生态和环境保护等问题提出了思路。笔者认为在岩土工程建设中,根据工程场地的地理、地质和生态环境条件,合理采用塑料排水材料,充分应用塑料排水技术,可以有效地保证工程设施的安全,实现环境岩土工程系统的相互促进和协调发展。文中同时介绍了塑料排水带真空和堆载预压地基固结渗透量的计算方法,可供参考。     

DEMAND SIGNALS FOR URBAN DRAINAGE AND FLOOD CONTROL PROJECTS1

ABSTRACT: Planning for urban drainage and flood control requires the use of a rational procedure for setting priorities and allocating funds. An innovative procedure developed by the Los Angeles County Flood Control District is described. It consists of the use of bond election voting results as a surrogate for demand signals representing the public preference for project approval. A regression equation has been developed to relate project characteristics to the likelihood of approval. The procedure is implemented through a “funnel-screen” review procedure which results in a list of reviewed and approved projects.     

DETERMINISTIC-SYSTEMIC RELATIONSHIPS IN OVERLAND FLOW ANALYSIS1

ABSTRACT: An analysis of storm runoff is presented, giving primary attention to deterministic-systemic relationships. So that system aspects can be emphasized, other aspects are kept simple; analysis is made for uniform rainfall on a strip of uniform width, limiting direct applicability to small areas. Two relationships between excess rain and time of concentration, one based on hydraulic parameters, the other on hydrologic characteristics, are combined in a solution for peak discharge. The hydraulic expression gives the interrelationship of time of concentration, excess rain, friction, length, and slope. The hydrologic relationship is achieved by converting ordinary intensity-duration curves to corresponding excess rain intensity-duration curves, thereby interrelating excess rain, time of concentration, and loss characteristics. The resulting solution for peak discharge allows for systemic feedback among both hydraulic and hydrologic parameters.     

A MODEL OF THE BEHAVIOR OF pH DETERMINING PARAMETERS IN IMPOUNDMENTS1

ABSTRACT: A computer model capable of describing the behavior of pH-determining parameters in an impoundment is presented. The steady-state model, based upon principles of water chemistry, applies the complete-mix concept to the routing of the chemical quantities, alkalinity and CO₂ acidity. An iterative procedure is used to account for surface mass transfer of carbon dioxide. A fourth-degree polynomial is solved for the hydrogen ion concentration at each point of routed alkalinity and CO₂ acidity concentrations. Field data required to verify and apply the model are described, including an example application to the Loyalhanna Creek Reservoir.     

HYDROLOGY OF TWO SMALL WETLAND BASINS IN EASTERN MASSACHUSETTS1

ABSTRACT: A hydrologic budget was prepared for two geologically different wetland basins in eastern Massachusetts for the 1971 water-year. Water table conditions prevailed at one wetland underlain by peat while an artesian system functioned at the other wetland which was underlain by muck. Hydrologic responses were generally similar at both wetlands, although each functioned differently in detail. Both wetlands exhibited high spring discharges and depressions of low flow. Ground water accounted for an estimated 93% of the total annual discharge from both wetlands; in late summer the peat deposit recharged the regional ground water body. Evapotranspiration in the spring was retarded in probable consequence of the extreme wetness of the wetland soils.     

PHOSPHORUS LOSSES FROM CROPLAND AS AFFECTED BY TILLAGE SYSTEM AND FERTILIZER APPLICATION METHOD1

ABSTRACT: A rainfall simulator was used to study the effectiveness of no-till and fertilizer application method on reducing phosphorus (P) losses from agricultural lands. Simulated rainfall was applied to 12 experimental field plots, each 0.01 ha in size. The plots were divided into no-till and conventional tillage systems. Two fertilizer application methods, subsurface injection and surface application, were investigated for the two tillage systems. Phosphorus fertilizer was applied at a rate of 46 kg/ha, 24 to 48 hours before the start of rain simulation. Water samples were collected from the base of each plot and analyzed for sediment and P content. No-till was found to be very effective in reducing runoff and sediment losses. No-till reduced sediment loss and total runoff volume by 92 and 67 percent, respectively. Subsurface injection of fertilizer, as compared to surface application, reduced PO₄ losses by 39 percent for no-till and by 35 percent for conventional tillage. The effect of tillage system on PO₄ losses was not significant. Reductions in total-P (P_T) losses due to no-till compared to the conventional tillage system were 89 and 91 percent for surface application and subsurface injection methods, respectively. Averaged across all fertilizer treatments, an equivalent of 0.9 and 8.9 percent of the P applied to the plots were lost from the no-till and conventional tillage plots, respectively.     

SATURATED SOIL HYDRAULIC CONDUCTWITY IN LOBLOLLY PINE PLANTATIONS ON DRAINED SITES1

ABSTRACT: Variation of in situ measured saturated hydraulic conductivity (KS) with stand age was examined in drained and intensively managed loblolly pine (Pinus taeda L.) plantations on very poorly drained Bayboro loam soils. Stand ages studied were 1-year-old and 14-years old. No differences in Ks values were found between the stand ages. In addition, no differences in core measured soil properties were found between the stand ages, indicating that there were no differences in the pore structure of the soil matrix. There was large variation of Ks within stands and between stands within ages. The mean within stand Ks values ranged from 0.66 cm/hr to 4.85 cm/hr. The frequency of tests exhibiting pipe flow through large non-capillary voids was significantly greater in the older stands; however, the continuity of the voids in the soil, and whether or not non-Darcy type flow would occur in a saturated profile, could not be determined.     

STREAMFLOW RESPONSE TO FOREST CUTTING AND REVEGETATION1

ABSTRACT: Experimental cuttings on two small, hardwood-forested watersheds in New England showed that annual streamflow can be increased as much as 41 percent. Most of the increase occurred in summer and early autumn when additional streamflow is most needed. Revegetation caused the annual increases to nearly disappear within 4 years after complete forest clearing.     

中国七大流域水系与洪涝的分维及其关系研究

本文在GIS技术的支持下，应用分形理论首先系统地计算了中国七大流域水系以及各流域洪涝的分维，其次对七大流域水系分维与各流域洪涝分维之间的可能关系进行了探讨。主要结论如下：（1）分维是表征洪涝发生特征的较好的参量，其蕴涵着洪涝发生次数，周期等丰富信息。（2）一般而言，在研究时段某流域洪涝发生的次数较多，则相应该流域洪涝的分维较大，反之亦然；（3）一般而言，当某一流域水系分维相对较小时，则相应该流域洪涝的分维相对较大，反之亦然。