Paweł Prokop

Abstract

The longest instrumental rainfall series have been investigated for the North Assam subdivision and 4 meteorological stations in Northeast India. Analysis of trends to annual and seasonal rainfall show these to be very stable, with no change in the rainfall over North Assam during the last 150 years. The Fourier analysis of fluctuations in rainfall series shows that the periodic signal of T=3.5 year is the strongest one. Such a signal, with the same phase, has been found for all rainfall stations of the North Assam subdivision and in all investigated seasons.

Keywords: monsoon rainfall, trend, periodicity, northeast India

Paweł Prokop [pawel@zg.pan.krakow.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences, Św. Jana 22, 31-018 Kraków, Poland
Adam Walanus, Institute of Archaeology, University of Rzeszów, Hoffmanowej 8, 35-016 Rzeszów

Abstract

The present paper includes a characterization of the environment in the extremely humid Cherrapunji region (with annual rainfalls from 8 000 to 24 000 mm), as well as a description of a new project and preliminary observations on runoff and soil erosion. Due to deforestation, soils are degraded. The investigation is based on existing meteorological records, measurements of rainfall intensity by way of pluviometers, and observations of selected geomorphological and hydrological processes conducted in an experimental catchment. Heavy rains mainly occur during late evening and continue till morning. The runoff follows the heavy rains immediately, even if the soil profiles may absorb 100 mm of rainfall over 3-4 hours. Deeper layers of the soil profile are still satura-ted during the first half of the dry season. During the rainy season, saturated sheet flow also prevails in the valley bottoms. The present-day rate of soil erosion is very low due to heavy overland How continuing for centuries, and the formation of a stony pavement on slope surfaces as well as of river channels cut in resistant rocks with iron crusts. This has been documented by measurement of ,rCs contents in soil profiles.

Keywords: rainstorm, overland flow, soil erosion, Cherrapunji plateau, '7Cs

Leszek Starkel [starkel@zg.pan.krakow.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences, Św. Jana 22, 31-018 Kraków, Poland
Surendra Singh, epartment of Geography, North-Eastern Hill University, Shillong-793014, India
Roman Soja [soja@zg.pan.krakow.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences, Św. Jana 22, 31-018 Kraków, Poland
Wojciech Froehlich, Homerka Laboratory of Fluvial Processes, Institute of Geography, Polish Academy of Sciences, Frycowa, Poland
Hiambok Syiemlieh, department of Geography, North-Eastern Hill University, Shillong-793014, India
Paweł Prokop [pawel@zg.pan.krakow.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences, Św. Jana 22, 31-018 Kraków, Poland