- 著者
- KUBO Sumiko K. Ch. V. NAGA KUMAR Gajji DEMUDU B. HEMA MALINI K. NAGESWARA RAO Ritesh AGRAWAL Ratheesh RAMAKRISHNAN A. S. RAJAWAT
- 出版者
- The Association of Japanese Geographers
- 雑誌
- Geographical review of Japan series B (ISSN:18834396)
- 巻号頁・発行日
- vol.90, no.2, pp.66-75, 2018-01-06 (Released:2017-12-29)
- 参考文献数
- 44
- 被引用文献数
- 1 4
Comparative analysis of time series satellite images spread over the past four decades indicated significant changes in the mangrove environment of the Krishna-Godavari twin deltas along the east coast of India. We analyzed Landsat-MSS, TM and ETM images from 1977, 1990, and 2000, respectively, and Indian Remote Sensing Satellite images from 1992, 2001, and 2013, which indicated that the mangrove cover in the region increased from 35,058 ha in 1977 to 39,283 ha by 2013. In spite of loss of mangrove vegetation over 8,036 ha due to coastal erosion, deforestation, decline and aquaculture encroachments, several mangrove-restoration projects taken up during 1991–2008 led to an overall increase in its area. Various mangrove eco-reforestation techniques were adapted in the region.
- 著者
- NAGUMO Naoko SUGAI Toshihiko KUBO Sumiko
- 出版者
- The Association of Japanese Geographers
- 雑誌
- Geographical review of Japan series B (ISSN:18834396)
- 巻号頁・発行日
- vol.87, no.2, pp.115-121, 2015 (Released:2015-07-04)
- 参考文献数
- 21
- 被引用文献数
- 3 5
Tributaries of Lake Tonle Sap in the Lower Mekong Basin are strongly influenced by seasonal changes of water level in Lake Tonle Sap and discharge of the Mekong River. The aim of this research was to gain a better understanding of the fluvial geomorphology of the Stung Sen River, a tributary of Lake Tonle Sap. We used stereopairs of aerial photographs and satellite images to identify the microtopography of the floodplain and riverbed, and field surveys to observe bankside topography and deposits. We recognized four types of channel bar in the lower Stung Seng River: lateral bars (type A), point bars (type B), concave-bank benches (type C), and diagonal and island bars (type D). Type A appears to have a complementary relationship with type D. In some instances types A and D bars transition to type B bars and, in rare instances, into type C bars. These changes are probably related to channel sinuosity and changes in the volume of transported sediment. Sediment transport and construction of the channel bars appears to be controlled by shifts of the flow regime of the Stung Sen River related to differences in the rate of water level rise in the river compared to those in Lake Tonle Sap. The riverine environment differs greatly from that of the floodplain, where sediment is deposited from suspension during periods of inundation.
- 著者
- KUBO Sumiko
- 出版者
- The Association of Japanese Geographers
- 雑誌
- Geographical review of Japan series B (ISSN:18834396)
- 巻号頁・発行日
- vol.84, no.2, pp.71-80, 2012 (Released:2012-03-31)
- 参考文献数
- 35
- 被引用文献数
- 2 5
A geomorphological survey map of the Arakawa Lowland (the lower Arakawa River basin in the Kanto Plain, central Japan) documents several groups of paleomeanders suggestive of channel shifts of the Arakawa River during historical times (last ca. 2,000 years). However, the sequence and timing of these changes of the river are unclear. I examined geomorphological features of paleomeanders and lithological analyses of natural levee deposits, along with historical records on channel modifications, to summarize the current state of knowledge. I differentiate four groups of paleomeanders with different meander wavelengths along the present Arakawa River. The set with the smallest wavelengths is on the Moto-Arakawa River, considered to be a distributary prior to river modifications starting in the 17th century. The second smallest is of late 19th century derived from earlier topographic maps. The set with middle-sized wavelengths can be correlated with the main trunk in the Middle Ages, and the set with the largest wavelengths is suggested to be from an ancient large river that combined the flows from the Tone and Arakawa Rivers. Lithological analyses of deposits along the large paleomeander indicate sediment input from the Tone River watershed. More historical and geomorphological evidence and dating results are required to confirm these arguments.