Connectivity of post-fire runoff and sediment from nested hillslopes and watersheds     

Codie Wilson  Stephanie K. Kampf  Sandra Ryan  Tim Covino  Lee H. MacDonald  Hunter Gleason 《水文研究》2021,35(1):e13975

Wildfire increases the potential connectivity of runoff and sediment throughout watersheds due to greater bare soil, runoff and erosion as compared to pre-fire conditions. This research examines the connectivity of post-fire runoff and sediment from hillslopes (< 1.5 ha; n = 31) and catchments (< 1000 ha; n = 10) within two watersheds (< 1500 ha) burned by the 2012 High Park Fire in northcentral Colorado, USA. Our objectives were to: (1) identify sources and quantify magnitudes of post-fire runoff and erosion at nested hillslopes and watersheds for two rain storms with varied duration, intensity and antecedent precipitation; and (2) assess the factors affecting the magnitude and connectivity of runoff and sediment across spatial scales for these two rain storms. The two summer storms that are the focus of this research occurred during the third summer after burning. The first storm had low intensity rainfall over 11 hours (return interval <1–2 years), whereas the second event had high intensity rainfall over 1 hour (return interval <1–10 years). The lower intensity storm was preceded by high antecedent rainfall and led to low hillslope sediment yields and channel incision at most locations, whereas the high intensity storm led to infiltration-excess overland flow, high sediment yields, in-stream sediment deposition and channel substrate fining. For both storms, hillslope-to-stream sediment delivery ratios and area-normalised cross-sectional channel change increased with the percent of catchment that burned at high severity. For the high intensity storm, hillslope-to-stream sediment delivery ratios decreased with unconfined channel length (%). The findings quantify post-fire connectivity and sediment delivery from hillslopes and streams, and highlight how different types of storms can cause varying magnitues and spatial patterns of sediment transport and deposition from hillslopes through stream channel networks.  相似文献   

Transient AT2018cow: A Scenario with an Equatorial Disk     

Urvachev  E. M.  Blinnikov  S. I.  Nomoto  K. 《Astronomy Letters》2021,47(11):738-745

Astronomy Letters - To explain the presence of early X-ray emission from the object AT2018cow, we have studied a scenario with the presence of dense ejecta in the system in the equatorial plane....  相似文献   

Resistance of Enzymes to Ionizing Radiation under Model Conditions of the Martian Regolith     

Cheptsov  V. S.  Belov  A. A.  Vorobyova  E. A.  Pavlov  A. K.  Tsurkov  D. A.  Frolov  D. A.  Lomasov  V. N.  Chumikov  A. E. 《Solar System Research》2021,55(5):383-388

Solar System Research - Ionizing radiation is one of the main factors that destroy biomolecules in extraterrestrial conditions. The effects of radiation depend on the conditions of the exposure...  相似文献   

基于双谱滤波的综合脉冲星时算法研究          下载免费PDF全文

周庆勇  魏子卿  张华  刘思伟  孙鹏飞  张奋  姜坤  刘晓刚  李奎 《天文学报》2021,62(2):19-95

毫秒脉冲星的自转频率非常稳定,提供了一种独立的基于遥远自然天体并能持续数百万乃至数十亿年的时间基准,具有稳定性强、运行时间长、服务范围广等特点.为了减弱毫秒脉冲星计时观测中各种高斯噪声对脉冲星时的影响,研究了一种基于双谱滤波的综合脉冲星时构建算法,处理分析了国际脉冲星计时阵(International Pul-sar Timing Array,IPTA)最新发布的4颗毫秒脉冲星(PSR J0437-4715、J0613-0200、J1713+0747和J1909-3744)的观测数据,分析了不同时间尺度综合脉冲星时的稳定性,并与构成国际原子时(International Atomic Time,TAI)的4家授时单位原子钟稳定性进行了比较.结果表明:双谱滤波算法能够较好地抑制观测噪声,提高综合脉冲星时的稳定性.相比于经典加权算法,综合脉冲星时1 yr、10 yr稳定度从7.77×10^-14、8.56×10^-16分别提高到1.50×10^-14、3.50×10^-16,单脉冲星时稳定性的提升也类似.同时发现,综合脉冲星时稳定性在5 yr及以上时间尺度上优于原子钟稳定性,可用于改善当前原子时的长期稳定性.  相似文献   

Drying increases organic colloidal mobilization in the karst vadose zone: Evidence from a 15-year cave-monitoring study     

Jin Liao  Chaoyong Hu  Xiuli Li  Jiaoyang Ruan 《水文研究》2021,35(4):e14163

Understanding the hydrological processes of colloids within the karst vadose zone is vital to the security of karst groundwater and providing appropriate paleohydrological explanations of colloid-facilitated metals in speleothem. This study addresses the mobilization mechanisms driving colloidal organic matter (COM) transport in the karst vadose zone using a 15-year long monthly monitoring dataset from a cave drip point (HS4) in Heshang Cave, Qingjiang Valley, China. Variations in COM concentrations were reported as the fluorescence difference values of raw and filtered (<0.22 μm) samples at an excitation wavelength of 320 nm and emission wavelength of ~400 nm. A fluorescence humification index (HIX) lower than 0.8 and an autochthonous index (BIX) higher than 1.2 indicated that the origin of COM was mainly from the karst vadose zone, rather than the soil zone. The COM concentration varied from 0.001 to 0.038 Raman Unit (RU), with evident seasonal fluctuations. Rising limbs for COM values occurred prior to rising limbs within a dripwater hydrograph; moreover, the COM peak values corresponding to the beginning of the increasing hydrograph generally suggested that the mobilization of COM reflected the movement of the air–water interface (AWI) in the karst vadose zone rather than rainfall intensity or flow velocity. COM peak values were positively correlated with the antecedent drying duration and negatively correlated with HIX values. These phenomena may be explained by the increased amount of organic matter that was aggregated and absorbed on the surface of carbonate in the karst vadose zone during a longer drying duration. Moreover, the longer drying duration was also beneficial to autochthonous biological activity, which subsequently decreased the HIX value of the organic matter in the karst vadose zone. The movement of AWI and the drying duration are both controlled by the outside weather conditions. This study is therefore conducive to evaluating the security of karst groundwater in response to climate change, and challenges prevailing paleoclimate interpretations of colloid-facilitated metal abundance timeseries reported from speleothems.  相似文献   

Large debris flows in Chosica,Lima, Peru: the application of hydraulic infrastructure for erosion control and disaster prevention     

S. P. Villacorta  K. G. Evans  K. Nakatani  I. Villanueva 《Australian Journal of Earth Sciences》2020,67(3):425-436

Abstract

Large debris flows in steep-sloped ravines debouching to the Rimac River, in metropolitan Lima (Peruvian capital), have resulted in considerable loss of life and property adversely impacting communities in the region. Temporal, spatial and volumetric features of debris flows are difficult to predict, and it is of utmost importance that achievable management solutions are found to reduce the impact of these catastrophic events. The emotional and economic toll of these debris flows on this increasingly densely populated capital city in South America is devastating where communities must live in such inadequate and dangerous conditions. To address this problem, the application of advanced Japanese technology, Sustainable Actions Basin Orientation (SABO), has been investigated using a geomorphological modelling to develop an implementation plan. Rayos de Sol stream basin in Chosica, was selected as a pilot to develop the proposal, as it is considered high risk due to the presence of ancient debris flows and recent flows in 2012, 2015 and 2017. The recurrence of debris flows in this location has resulted in numerous deaths and catastrophic property losses. This study combines geologic and geomorphic mapping and hydraulic and landform evolution numerical modelling. The implementation of a SABO Master Plan based on the multidisciplinary assessment hazard scenarios, will allow the implementation of feasible mitigation actions. The SABO technology has been applied successfully in Japan and other countries in areas with steep short slopes, similar to the conditions surrounding the Peruvian capital. Results from this study will be presented to the Peruvian Government as part of an action plan to manage debris-flow impact.

1. KEY POINTS

2. High-risk mass slope failure is linked to poor urban planning in urban developing regions of Lima the capital of Peru.

3. A multidisciplinary study including geotechnical and hydrological analysis, engineering design, and socio-economic research is required to implement a SABO Master Plan, and this basin is pilot study basin.

4. At the present time, a maintenance programme for existing hydraulic structures should be implemented, and a flood risk management plan developed may propose the relocation of some communities and infrastructure.

  相似文献   

Analysis of one-dimensional models for exchange flows under strong stratification     

Kaptein  Steven J.  van de Wal  Koen J.  Kamp  Leon P. J.  Armenio  Vincenzo  Clercx  Herman J. H.  Duran-Matute  Matias 《Ocean Dynamics》2020,70(1):41-56

Ocean Dynamics - One-dimensional models of exchange flows driven by horizontal density gradients are well known for performing poorly in situations with weak turbulent mixing. The main issue with...  相似文献   

Determination of the Thermophysical Characteristics of the Lunar Soil Using Solar Heat     

Dudkin  K. K.  Alifanov  O. M. 《Solar System Research》2020,54(7):630-636

Solar System Research - The possibility of determining the thermophysical characteristics of the lunar soil by a penetrating probe when using solar heat as a heater is considered. The effectiveness...  相似文献   

Medium-Resolution Optical Range Space Images: Consumer Expectations     

Selin  V. A.  Emelyanov  A. A.  Sizov  O. S.  Emelyanov  K. S.  Borisov  A. V. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(9):1182-1189

Izvestiya, Atmospheric and Oceanic Physics - Our survey of various space image consumers identified that the geographic coverage, regularity, and frequency of observations are the most important...  相似文献   

Reliable Determination of Paleointensity in Igneous Rocks Bearing Thermochemical Remanent Magnetization     

Shcherbakov  V. P.  Sycheva  N. K.  Afinogenova  N. A. 《Doklady Earth Sciences》2020,495(2):918-920

Doklady Earth Sciences - Oxidation decomposition of titanomagnetite grains to the magnetite–ilmenite lattice during the formation of igneous rock can lead to thermochemical remanent...  相似文献