Identifying the driving factors of sediment delivery ratio on individual flood events in a long-term monitoring headwater basin

The Sediment Delivery Ratio(SDR) has multi-fold environmental implications both in evaluating the soil and water losses and the effectiveness of conservation measures in watersheds. Various factors, including hydrological regime and watershed properties, may influence the SDR at interannual timescales. However, the effect of certain important dynamic factors, such as rainfall peak distribution, runoff erosion power and sediment bulk density, on the sediment delivery ratio of single flood events(SDRe) has received little attention. The Qiaogou headwater basin is in the hilly-gully region of the Chinese Loess Plateau, and it encompasses a 0.45 km^2 catchment. Three large-scale field runoff plots at different geomorphological positions were chosen to obtain the observation data, and the 20-year period between 1986 and 2005 is presented. The results showed that the SDRe of the Qiaogou headwaters varied from 0.49 to 2.77. Among the numerous influential factors, rainfall and runoff were the driving factors causing slope erosion and sediment transport. The rainfall erosivity had a significant positive relationship with the sediment transport modulus(R^2=0.85, P<0.01) but had no significant relationship with SDRe. The rainfall peak coefficient was significantly positively correlated with the SDRe(R^2=0.64, P<0.05), indicating the influence of rainfall energy distribution on the SDRe. The runoff erosion power index was not only significantly related to the sediment transport modulus(R^2=0.84, P<0.01) but also significantly related to the SDRe(R^2=0.57, P<0.01). In addition, the relative bulk density was significantly related to the SDRe, indicating that hyper-concentrated flow characteristics contributed to more transported sediment in the catchment. Thus, the rainfall peak coefficient, runoff erosion power and sediment relative bulk density could be used as dynamic indexes to predict the SDRe in the hilly areas of the Chinese Loess Plateau.

The Seasonal Rainfall Forecast in Nanning City in 2019 with the Method of Trend Comparison Ratio (TCR)

In this paper, the monthly rainfall statistical data of Nanning City, Capital of Guangxi Zhuang Autonomous Region, China, from 2006 to 2018, were collected. On the basis of qualitative analysis of the rainfall seasonal changing law, the non-linear seasonal rainfall forecast model on Nanning City with the method of Trend Comparison Ratio (TCR) was established by the statistical analysis software Office Excel 2013. The model was used to predict the rainfall in spring, summer, autumn and winter in Nanning in 2019. The results were: 286.41 mm, 695.79 mm, 292.20 mm and 118.11 mm, respectively. It was also found that the predicted results were consistent with the seasonal distribution characteristics, annual distribution characteristics and the trend of historical rainfall time series fluctuation, through the qualitative analysis of figures. Compared with the actual measured rainfall data of Nanning City in 2019 in the China Statistical Yearbook (2020), the predicted values are basically consistent with the measured values.

Snowfall Shift and Precipitation Variability over Sikkim Himalaya Attributed to Elevation-Dependent Warming

Sikkim Himalaya hosts critical water resources such as glacial,rain,and snow-fed springs and lakes.Climate change is adversely affecting these resources in various ways,and elevation-dependent warming is prominent among them.This study is a discussion of the elevation-dependent warming(EDW),snowfall shift,and precipitation variability over Sikkim Himalaya using a high-resolution ERA5-land dataset.Furthermore,the findings show that the Sikkim Himalaya region is experiencing a warming trend from south to north.The majority of the Sikkim Himalayan region shows a declining trend in snowfall.A positive advancement in snowfall trend(at a rate of 1 mm per decade)has been noticed above 4500 meters.The S/P ratio indicates a shift in snowfall patterns,moving from lower elevations to much higher regions.This suggests that snowfall has also transitioned from Lachung and Lachen(3600 m)to higher elevated areas.Moreover,the seasonal shifting of snowfall in the recent decade is seen from January-March(JFM)to February-April(FMA).Subsequently,the preceding 21 years are being marked by a significant spatiotemporal change in temperature,precipitation,and snowfall.The potent negative correlation coefficient between temperature and snowfall(–0.9),temperature and S/P ratio(–0.5)suggested the changing nature of snowfall from solid to liquid,which further resulted in increased lower elevation precipitation.The entire Sikkim region is transitioning from a cold-dry to a warm-wet weather pattern.In the climate change scenario,a drop in the S/P ratio with altitude will continue to explain the rise in temperature over mountainous regions.

Surface Treatments Effect on Rainfall Canopy Interception and Runoff-Rainfall Ratio for in-Field Rainwater Harvesting

The purpose of this study was to ascertain the effectiveness of surface treatments to quantify the partitioning of rainwater falling on the runoff strips and basins as well as to determine the fraction of rainwater available to intercept by maize canopy and infiltrate into the root zone. The rainfall canopy interception （RCI） was estimated as a function of basin leaf area ratio per rain event. The runoffrainfall （RR） ratio was determined for both a single rainfall event and the whole growing season. Infiltration ratio of basin to runoff area was analysed for every unit millimeter of water that infiltrate in the runoff section, some additional of water will infiltrate in the basin area. The plateau value of RCI-rainfall relationships rendered about double in the wider （1.0-1.1 mm） compared to the narrow runoff strips （0.5-0.6 mm）. Statistically, the combined surface treatments （RSL x ML） affected the RR ratio with higher efficiency in bare 1 m runoff （27%） and the lower efficiency group （〈 10%） is associated with the widest runoff length covered with mulch. Variations in fractions of rainwater that can infiltrate into basins and runoffareas can lead one to select alternative strategies for water harvesting techniques.

Characteristics of Caragana korshinskii and Hippophae rhamnoides stemflow and their significance in soil moisture enhancement in Loess Plateau, China

Stemflow of xerophytic shrubs represents a significant component of water replenishment to the soil-root system and influences water utilization of plant roots at the stand scale,especially in water-scarce semi-arid ecosystems.The stemflow of two semi-arid shrubs(Caragana korshinskii and Hippophae rhamnoides)and its effect on soil moisture enhancement were evaluated during the growing season of 2011 in the semi-arid loess region of China.The results indicated that stemflow averaged 12.3%and 8.4%of the bulk precipitation for C.korshinskii and H.rhamnoides,respectively.Individual stemflow increased in a linear function with increasing rainfall depth.The relationship between funneling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for both C.korshinskii and H.rhamnoides.Averaged funneling ratios were 156.6±57.1 and49.5±30.8 for C.korshinskii and H.rhamnoides,respectively,indicating that the canopy architecture of the two shrubs was an effective funnel to channel stemflow to the root area,and C.korshinskii showed a greater potential to use stemflow water in the semi-arid conditions.For individual rainfall events,the wetting front depths were approximately 2 times deeper in the rooting zone around the stems than in the bare area outside canopy for both C.korshinskii and H.rhamnoides.Correspondingly,soil water content was also significantly higher in the root area around the shrub stem than in the area outside the shrub canopy.This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under semi-arid conditions.

Estimation of USLE crop and management factor values for crop rotation systems in China

Soil erosion on cropland is a major source of environmental problems in China ranging from the losses of a non-renewable resource and of nutrients at the source to contamination of downstream areas. Regional soil loss assessments using the Universal Soil Loss Equation (USLE) would supply a scientiifc basis for soil conservation planning. However, a lack of in-formation on the cover and management (C) factor for cropland, one of the most important factors in the USLE, has limited accurate regional assessments in China due to the large number of crops grown and their complicated rotation systems. In this study, single crop soil loss ratios (SLRs) were col ected and quantiifed for 10 primary crops from past studies or re-ports. The mean annual C values for 88 crop rotation systems in 12 cropping system regions were estimated based on the combined effects of single crop SLRs and the percentage of annual rainfal erosivity (R) during the corresponding periods for each system. The C values in different cropping system regions were compared and discussed. The results indicated that the SLRs of the 10 primary crops ranged from 0.15 to 0.74. The mean annual C value for al 88 crop rotation systems was 0.34, with a standard deviation of 0.12. The mean C values in the single, double and triple cropping zones were 0.37, 0.36 and 0.28, respectively, and the C value in the triple zone was signiifcantly different from those in single and double zones. The C values of dryland crop systems exhibited signiifcant differences in the single and triple cropping system regions but the differences in the double regions were not signiifcant. This study is the ifrst report of the C values of crop rotation systems in China at the national scale. It wil provide necessary and practical parameters for accurately assessing regional soil losses from cropland to guide soil conservation plans and to optimize crop rotation systems.

Changes in the Proportion of Precipitation Occurring as Rain in Northern Canada during Spring–Summer from 1979–2015

Changes in the form of precipitation have a considerable impact on the Arctic cryosphere and ecological system by influencing the energy balance and surface runoff. In this study, station observations and ERA-Interim data were used to analyze changes in the rainfall to precipitation ratio（RPR） in northern Canada during the spring–summer season（March–July）from 1979–2015. Our results indicate that ERA-Interim describes the spring–summer variations and trends in temperature and the RPR well. Both the spring–summer mean temperature [0.4℃–1℃（10 yr）^（-1）] and the RPR [2%–6%（10 yr）^（-1）] increased significantly in the Canadian Arctic Archipelago from 1979–2015. Moreover, we suggest that, aside from the contribution of climate warming, the North Atlantic Oscillation is probably another key factor influencing temporal and spatial differences in the RPR over northern Canada.

Canopy interception loss in a Pinus sylvestris var. mongolica forest of Northeast China

Pinus sylvestris var. mongolica is one of the main species to be afforested in deserts of China. But little work has been carried out on the canopy interception loss of this plant species. For researching the canopy interception loss of a natural P. sylvestris forest, we observed the gross precipitation, gross snowfall, throughfall and stemflow in a sample plot at the Forest Ecosystem Research Station of Mohe in the Great Khingan Mountains of Northeast China from July 2012 to September 2013. Considering the spatial variability of the throughfall, we increased the area rather than the number of collector and randomly relocated them once a week. The results demonstrated that the throughfall, stemflow, and derived estimates of rainfall and snowfall interception loss during the main rainy and snowy seasons were 77.12%±5.70%, 0.80%, 22.08%±5.51% and 21.39%±1.21% of the incident rainfall or snowfall, respectively. The stemflow didn＇t occur unless the accumulated rainfall reached up to 4.8 mm. And when the gross precipitation became rich enough, the stemflow increased with increasing tree diameters. Our analysis revealed that throughfall was not observed when rainfall was no more than 0.99 mm, indicating that the canopy storage capacity at saturation was 0.99 mm for P. sylvestris forest.

Upper Bound Solution of Soil Slope Stability under Coupling Effect of Rainfall and Earthquake

Based on the limit analysis upper bound method,a new model of soil slope collapse has been proposed which consists of two rigid block zones and a plastic shear zone.Soil slope was induced failure by coupling effect of rainfall and earthquake,and these blocks were also incorporated horizontal earthquake force and vertical gravitate.The velocities and forces were analyzed in three blocks,and the expression of velocity discontinuities was obtained by the principle of incompressibility.The external force work for the blocks,the internal energy of the plastic shear zone and the velocity discontinuous were solved.The present stability ratios are compared to the prevenient research,which shows the superiority of the mechanism and rationality of the analysis.The critical height of the soil slope can provide theoretical basis for slope support and design.

Effects of soil conservation practices on soil erosion and the size selectivity of eroded sediment on cultivated slopes

Soil conservation practices can greatly affect the soil erosion process,but limited information is available about its influence on the particle size distribution(PSD)of eroded sediment,especially under natural rainfall.In this study,the runoff,sediment yields,and effective/ultimate PSD were measured under two conventional tillage practices,downhill ridge tillage(DT)and plat tillage(PT)and three soil conservation practices,contour ridge tillage(CT),mulching with downhill ridge tillage(MDT),and mulching with contour ridge tillage(MCT)during 21 natural rainfall events in the lower Jinsha River.The results showed that(1)soil conservation practices had a significant effect on soil erosion.The conventional tillage of DT caused highest runoff depth(0.58 to 29.13 mm)and sediment yield(0.01 to 3.19 t hm^(-2)).Compared with DT,the annual runoff depths and sediment yields of CT,MDT and MCT decreased by 12.24%-49.75%and 40.79%-88.30%,respectively.(2)Soil conservation practices can reduce the decomposition of aggregates in sediments.The ratios of effective and ultimate particle size(E/U)of siltand sand-sized particles of DT and PT plots were close to 1,indicating that they were transported as primary particles,however,values lower/greater than 1 subject to CT,MDT and MCT plots indicated they were transported as aggregates.The ratios of E/U of claysized particles were all less than 1 independently of tillage practices.(3)The sediments of soil conservation practices were more selective than those of conventional tillage practices.For CT,MDT and MCT plots,the average enrichment ratios(ERs)of clay,silt and sand were 1.99,1.93 and 0.42,respectively,with enrichment of clay and silt and depletion of sand in sediments.However,the compositions of the eroded sediments of DT and PT plots were similar to that of the original soil.These findings support the use of both effective and ultimate particle size distributions for studying the size selectivity of eroded sediment,and provide a scientific basis for revealing the erosion mechanism in the purple soil area of China.

Analysis of Precipitation Resource and Weather Modification Potential in Anyang

Using ground water vapor pressure and precipitation data at four times of one day during 1985- 2014 in each county（ city） of Anyang,precipitable water at each station was calculated,and temporal-spatial distribution of atmospheric maximum precipitable water and its change trend over the years in the city were analyzed. Results showed that atmospheric maximum precipitable water in Anyang City had the characteristics of summer far more than winter,autumn slightly higher than spring,west and south more,and east and north less,and presented the increasing trend year by year. We further analyzed the characteristic of monthly rainfall enhancement potential in each county,and mean in whole year was 80%. In spring and winter,rainfall enhancement potential in the west was bigger than east,while rainfall enhancement potential in the east was bigger than west in summer and autumn. The research provides reference basis for rationally carrying out artificial rainfall work,which could effectively ease uneven temporal-spatial distribution problem of water resource in Anyang City.

2022年初5次降雪过程分析和预报着眼点

本文采用ECMWF(European Centre for Medium-Range Weather Forecasts)细网格和NCEP(National Centers for Environmental Prediction)模式数据、NCEP 1°×1°再分析资料、降雪加密观测和常规资料,对2022年初的5次降雪过程进行对比分析,发现5次降雪过程均为雨转雪过程,且持续时间相对较短,平原为雨夹雪或小雪到中雪,山区中到大雪,局部暴雪,数值模式预报的积雪深度与实况相差甚远;大尺度环流形势为500 hPa中低纬南支槽或弱波动配合700 hPa上的暖湿气流和中低层冷空气,造成边界层浅薄的冷垫上温度骤降而在短时间内形成降雪;相较于平原地区,高山区上空温度层结与最大上升运动中心的配置,有利于降雪粒子较长时间维持在有利于枝状雪花的形成区域,且高山区云底云水含量显著偏低、整层温度足够低,故高山区更利于暴雪的形成。

气候变暖对吉林省降雪量与新增雪深关系的影响

降雪量和积雪深度的关系是降雪预报及水文气候模拟中的重要参数。本文利用吉林省50个站点1961—2021年的降水量、积雪深度、气温、风速和天气现象等气象观测资料,分析了降雪量和新增积雪深度的关系及主要气候影响因子。结果表明,在中等及以上强度的降雪过程中,吉林省新增积雪深度(D)与降雪量(S)的比值(深量比,Rds)平均为0.96 cm·mm^(-1);该比值存在空间差异,呈西部小东部大的分布特征,且存在明显的月际、年际和年代际变化特征,其中月际变化呈现不对称的抛物线型,12月和1月为大值时段;近60年来Rds呈减小趋势,变化速率为-0.01 cm·mm^(-1)·(10a)^(-1);降雪日Rds与气温呈明显反相关关系,其中在-12~0℃的温度区间,Rds随气温上升呈明显减小趋势。气候变暖、降水量增加和风速的减小是降雪过程中降雪量与新增雪深关系年代际变化的直接原因。揭示降雪量和新增雪深的关系对于认识东北亚中高纬度降雪积雪特征及其成因具有重要意义。

2024年初两次雨雪冰冻天气过程对公路通行影响的对比分析

2024年1月31日-2月5日、2月18-25日我国先后出现两次大范围雨雪冰冻天气过程(分别简称0131"过程和"0218"过程),两次过程具有相态复杂、雨雪量大、影响范围广、持续时间长等特点。利用全国2430个国家气象站观测数据以及交通流量和公路阻断信息,对比分析了两次雨雪冰冻天气过程对公路通行的影响;同时,选取降雪量、冻雨、积雪深度、地面温度、地面结冰作为影响公路通行的气象指标,构建冰雪天气指数,探讨冰雪天气强度与公路通行影响的关系。结果表明:两次过程发生于春节前后人口流动高峰期,"0218"过程影响范围更广,造成交通流量的降低幅度总体高于"0131"过程;两次过程中陕西、山西、河南、湖北、湖南以及贵州6省公路通行受积雪或结冰影响严重,路段封闭段次多,但影响程度存在地区差异,其中山西、河南、湖北、湖南"0131"过程影响更重,陕西、贵州"0218"过程影响更重;两次过程中冰雪天气指数强度与公路阻断影响度的变化趋势一致,与交通流量变化率呈反比,反映出冰雪天气指数对于冰雪天气下的公路交通影响研判具有良好指示意义。

Decrease in snowfall/rainfall ratio in the Tibetan Plateau from 1961 to 2013

On the basis of two gridded datasets of daily precipitation and temperature with a spatial resolution of 0.5°×0.5°, and meteorological station data released by the National Meteorological Information Center （NMIC） during 1961-2013, the spatial and temporal variations of total amount of precipitation, amount of rainfall, amount of snowfall and snowfall/rainfall ratio （S/R） in the Tibetan Plateau （TP） are analyzed using Sen＇s slope, the Mann-Kendall mutation test, Inverse Distance Weighting （IDW） and the Morlet wavelet. Total amount of precipitation and amount of rainfall generally show statistically significant increasing trends of 0.6 mm·a^-1 and 1.3 mm·a^-1, respectively, while amount of snowfall and SIR have significant decreasing trends of-0.6 mm·a^-1 and -0.5% a^-1, respectively. In most regions, due to significant increasing trends in total amount of precipitation and amount of rainfall, and significant decreasing trends in amount of snowfall, SIR shows a decreasing trend in the TP. Abrupt changes in total amount of precipitation, amount of rainfall, amount of snowfall and S/R are detected for 2005, 2004, 1996 and 1998, respectively. Total amount of precipitation, amount of rainfall, amount of snowfall and SIR are concentrated in cycles of approximately 5 years, 10 years, 16 years and 20 years, respectively. The trend magnitudes for total amount of precipitation and amount of rainfall all show decreasing-to-increasing trends with elevation, while amount of snowfall and SIR show decreasing trends.

2024年2月初河南一次罕见雨雪冰冻过程诊断分析

2024年1月31日-2月5日河南出现了一次罕见的雨雪冰冻天气,表现为持续时间长、累积雨雪量大、积雪深、温度低、降水相态复杂等特点。利用国家气象站和双偏振雷达观测数据以及ERA5再分析资料,对本次过程的极端性及降水相态演变、雨雪冰冻成因进行了诊断分析,结果表明:(1)过程期间有5个国家气象站最大积雪深度达到或突破2月历史同期极值,多站最高气温达到或刷新2月上旬历史同期最小值;单日至少有68.3%的国家气象站出现降水,单站最长连续降水近29h。(2)大尺度环流系统稳定维持是本次过程发生发展的重要原因之一;对流层低层强冷空气持续入侵不仅起到动力抬升作用,也为雨雪冰冻天气提供了持续降温条件;异常强盛的偏南气流为本次过程提供了充足的水汽和动量,同时也增强了不稳定层结。(3)使用单一特性层温度来判识降水相态依据不足,应根据整层大气层结温度来预判可能出现的降水相态,当整层大气温度均低于0℃时降水相态为纯雪,若存在温度高于0℃的融化层或云体由过冷却水滴组成时,将出现混合型降水相态。(4)双偏振雷达的相关系数和差分反射率产品对区分雨夹雪和纯雪有较好的指示意义,当相关系数接近1、差分反射率为-1~0dB时,为纯雪;当相关系数小于1、差分反射率大于1dB时,为雨夹雪。

青藏高原雪水比例时空变化特征

为厘清青藏高原地区不同相态降水及其变化规律,本文基于第三极地区长时间序列(1979—2020年)高分辨率(1/30°,日)地面气象要素驱动数据集,采用基于表面高程和气象条件的雨雪识别方法,识别了青藏高原地区的降雨和降雪,分析了青藏高原雪水比例(SPR)的分布特征和时空演变规律。结果表明:①SPR空间分布差异显著,西高东低;②SPR整体呈下降趋势,平均以1.11%/(10 a)的速率显著降低;③冷、暖季均呈现降雨增加、降雪减少、SPR降低趋势,但暖季的变化速率和显著性高于冷季;④高原东西部降雪量在冷、暖季相当,高原中部以暖季降雪为主,高原暖季降雨量约占全年的90%,高原大部分地区暖季降雪占全年降雪的比例呈下降趋势(-0.29%/(10 a))。研究结果有望为区域气候变化和水科学研究提供科学依据。

“12·14”山东暴雪过程的极端性特征及成因

利用国家级地面气象观测站、风廓线雷达、X波段双偏振相控阵雷达等多源观测资料和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析(ECMWF Reanalysis v5,ERA5)资料,总结了2023年12月13—14日山东大范围暴雪、局地大暴雪(简称“12·14”暴雪)极端性的特征和成因,并与2021年11月7日山东极端暴雪过程(简称“11·7”暴雪)对比分析了降雪量和雪水比差异的原因。结果表明:(1)典型的暖平流型天气形势是产生极端暴雪有利的环流背景条件,低层切变线和风速辐合区在鲁西北叠加,形成强烈而持久的上升运动。(2)低空急流异常偏强,降水强度不仅与低空急流的强度有关,而且与其厚度有关。当3.0 km高度保持低空急流的强度时,10 m·s^(-1)风速到达的高度越低,降雪强度越大。(3)700 hPa比湿超过4 g·kg-1、850 hPa比湿超过3 g·kg-1的持续时间均长达10 h以上,为极端暴雪过程提供了充足的水汽。850 hPa比湿和比湿平流远远高于“12·14”暴雪过程,是“11·7”过程最大累计降雪量大于“12·14”过程的原因之一。(4)“12·14”暴雪过程垂直运动旺盛,最大上升速度位于不稳定层顶的前沿,处于-20~-10℃层,有利于树枝状冰晶生长,降雪效率高。对流层整层温度低于0℃,雪花下落过程中没有融化,雪水比高,积雪深度大。“11·7”暴雪过程初期最大上升运动中心高度低,形成更多柱状冰晶,经过暖层时融化,雪水比低,积雪深度小于“12·14”暴雪过程。

河南北中部一次雨雪冰冻过程的相态特征分析

2023年末河南北中部出现一次大范围雨雪冰冻过程,降水相态复杂多变,并伴有区域性雷暴,较为罕见。利用常规观测、ERA5再分析以及风廓线雷达和双偏振雷达资料等对此次过程的相态特征及成因进行分析。结果表明:(1)500 hPa横槽转竖、南支槽东移,700 hPa西南急流发展,地面先后受东路及西路冷空气影响,导致河南北中部出现持续性大范围雨雪冰冻天气。(2)冷垫以上的条件不稳定性、锋区附近的条件对称不稳定以及强锋生环流上升支为对流天气发生发展提供有利条件,是强雨雪、雷暴及冰雹产生的主要原因。(3)过程中冻雨对应“厚暖层(100-200 hPa)-冷层”层结结构,冰粒对应“冰晶层-薄暖层(50-100 hPa)-冷层”结构,纯雪对应整层冷层,雨夹雪对应近地面出现浅薄暖层。(4)风廓线雷达水平风场产品可定性反映低层西南急流和近地面冷空气强度的变化,不同相态降水的垂直速度产品差异明显,可为相态转变短临的监测和预报提供参考。(5)双偏振产品显示,冻雨和纯雪对应相关系数最大(≥0.99),雨夹雪相关系数最小(0.85~0.9);冰粒中层融化层显著,其高度处差分反射率因子最大,相关系数最小。

考虑风场作用的城市建筑区产流特征

为探究风场与建筑物对城市建筑区产流的影响,采取理论与实验相结合的研究方法,考虑风场与建筑区特征,提出一个建筑区产流计算公式。通过降雨径流实验对公式的合理性进行验证,实验结果与公式计算结果相近,表明公式在一定程度上反映建筑区产流特征。对于独栋建筑与松散建筑区,风场对产流有直接影响,建筑区产流量随降雨倾角增大而减小;对于密集建筑区,建筑区产流受风场与建筑区自身特征影响,产流量随建筑密度增加呈先增后减的趋势。在不同降雨倾角与不同建筑密度下,对建筑区产流进行计算,结果表明:降雨倾角不同时,建筑密度对产流量影响也不同;降雨倾角较大时,密集建筑区产流量随建筑密度增大而增大。