Spatial dynamics of land use in river basin area influences overflow and river flow. In extreme condition, the change of balance between rain and overflow will run fast so it threatens humans and the environment.
According to Dra. Dewi Liesnoor Setyowati, M.Si, a lecturer of Geography Department, Faculty of Social Sciences, Semarang State University, spatial dynamics phenomenon of land use will affect overland flow. In densely vegetated land, rainwater will be retained by the vegetation and absorbed into the ground through decomposed leaves on the soil surface, which causes minor overflow. Meanwhile, in open land or bare land, most of rainwater will become surface overflow that flows to the river so the river flows fast. ‘All of this is due to human need for land for their settlement and their increased activities,†said Dewi Liesnoor, Saturday (13/2) at Faculty of Geography, UGM, in her open examination of doctoral program.
Her research of Kreo river basin in Semarang city, Ungaran Regency and Kendal Regency showed the tendency of spatial dynamics of land use in Kreo, which is the decrease of forested area measuring 62.9 ha or 6.6%, open land 114.6 ha or 69.4%, grass/bush/shrub 38.4 ha or 27.1%, rice field 86.1 ha or 4.4%, and dry field 19.2 ha or 5.3%. The increase of land use is found in mixed plantation: 27.6 ha (1.2%), regular settlement 43.3 ha, irregular settlement 80.8 ha (13.1%) and plantation 169.5 ha (58.2%).
She said that the change of land use in Kreo river basin was followed by the increased surface flow, which increased the maximum debit of river flow. This was showed by Kreo River's debit, particularly in year 1993, 2001, 2003 and 2006. Kreo has the potential to supply 40% of flow to Garang River. “Therefore, researches on land use studies on overflow is very much needed,†said the lady born in Yogyakarta, 11 August 1962.
In her dissertation entitled “Relationship between Rain and Overflow in various Spatial Dynamics of Land Use in Kreo River Basin, Central Javaâ€, Dewi Liesnoor suggested to reduce forest land which can potentially increase overflow. Therefore, vegetated areas and decomposed leaves need to be maintained to absorb water into the ground. Residential buildings need to be re-arranged, too. She suggested that residential buildings are designed as rural instead of urban residences.