International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004 
  
  
Changes in hydrological conditions 
The upper Betna has almost dried up above Kolaroa, 
drains only rainwater during rainy season. The 
middle part below Kolaroa is partly tidal but 
poldering at the down stream has induced rapid 
siltation of the channel. This has deteriorated the 
local drainage condition of the flood plains (Hossain 
1998). Similar poldering effects are also evident in 
the immediate south of the Satkhira town where a 
vast embankment area become silted up, rendering 
the channels unfit for navigation and created serious 
water logging in the interior tidal plain (Figure 5). 
The water logged areas are in an around Jhaudanga, 
Raghunathpur, Kamarbaisa, Labsha, Dattadanga, 
Daulatpur, Korivila, Nevakhali, Bejudanga, 
Dhakakula. It was observed from the field that from 
Jhaudanga down to Gopinathpur, vast pockets of 
area, varying in size, remains water logged mainly 
due to the construction of the water control structure 
at the downstream. The local inhabitants also 
reported that Rajnagar, Bultipara, Kheterdanga, 
Khajurdanga, Kaikhali, Shibnagar and Taltala 
remains water logged from middle of June to 
October. So these new water logged areas are the 
out come of deteriorating river condition of the area. 
The embankment, although given protection against 
saline water intrusion, but it has deprived the 
interior plains effectively from two important 
benefits: 
a. In the tidal exchange between sea and 
tidal plain at the interior, huge finer silts 
are added to the valley bottom and 
thereby, low-lying area gains height. This 
process of valley infilling goes on until 
land raise up. In the present context, as 
tidal water cannot get in to the tidal plains, 
thus silt laden tidal water deposits silts on 
the channel bed instead of tidal plain, 
thereby, drainage behind the channel 
remains a problem, and the hydraulic 
behavior become more erratic, particularly 
bank erosion expedites. 
b. Again, in the form of tidal exchange, the 
sea actually transports oxygenated water 
to the tidal wetlands wherein biotic life 
requires oxygen for respiration and local 
organic substances and detritus are 
decomposed through this  water.In 
exchange, nitrate and phosphate rich 
wetland water are transported back to the 
estuaries which are essential to the near- 
shore marine life (Slaymaker 1996). 
828 
6. Discussion and Conclusion: 
a) The Kholpetua river basin has three distrinct 
physical setting — Fresh water, semi-saline/brackish 
and saline zone. Extensive shrimp farming practices 
in semi-saline zone are gradually pushing both 
laterally and upwards causing alteration of the 
characteristic fresh water habitats and the semi- 
saline characteristics as well. 
b) Poldering of the tidal rivers have affected the 
drainage efficiency at lower order, causing serious 
drainage congestion in the tidal wetlands and 
enhance siltation in the tidal channels. 
c) From estuarine ecological point, poldering also 
affects nutrient exchange between tidal wetlands 
and estuaries and Bay. 
d) In the last 3 hundred years the mangrove forest 
has been cleared southward very rapidly. From 1779 
to 1872 a strip of about 10 km wide mangrove forest 
has been disappeared and up till now another strip 
of similar extent has gone. 
References: 
1. B.B.S. 2001. Statistical yearbook of 
Bangladesh, Ministry of Planning, 
Government of Bangladesh, Dhaka. 
Cooke R.U. and DoornKemp 1974: 
Geomorphology in environmental 
management- an introduction. Clarendon: 
Oxford. 
3. Delta Development Project 1985: Shrimp 
culture in the semi-saline zine of the 
delta. Tech. Rpt. 13 (vol. 1). The Hague 
4. FAO, 1988: Agro-ecological Regions of 
Bangladesh, Report 2. 
5. Hossain M.D. 1998. Remote Sensing 
Application for Hydro-Geomorphological 
analysis: a case study on Satkhira sadar 
thana. M.Phil. Thesis, Dept. of 
Geography & Environment, 
Jahangirnagar University. 
6. Rennells J.1779: Map of Bengal and 
Bahar. Surveyor Generals Office, 
Calcutta, India. 
7. iSlaymaker ....O. 
Hazards. P.348-365. 
London. 
8... Thuilier.. . HL. 1872: 
Pergunnahs, Jessore, 
Noacolly and Soonderbuns. 
Generals Office, Calcutta, India. 
9. WARPO 2000. National Water 
Resources Database, Ministry of Water 
Resources, Government of Bangladesh. 
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