MAJOR CAUSES OF LAND LOSS 



The three primary causes of land loss in Texas and elsewhere are (I) reductions in 

 sediment supply, (2) relative sea-level rise and (3) human activities; although listed 

 separately the third category directly affects the other two (Figure 3). Of foremost 

 importance is the natural decrease in sediment supply that accompanied climatic changes 

 over the past few thousand years. Simply put, the major coastal rivers and nearshore 

 currents are no longer delivering the volume of sediment that they once did. This natural 

 decrease in sediment supply has been aggravated to varying degrees by dam construction 

 and entraining of rivers and emplacement of jetties, groins, and seawalls that 

 compartmentalize the coast and disrupt the longshore transport of sand. Hence, these 

 structures have locally contributed to shoreline erosion and their contribution to land loss 

 may be even greater in the future. 



SOURCES 

 riverine discharge 

 shoreline erosion 

 onshore transport 

 eolian processes 



SINKS 



shoreline accretion 

 storm wQshover 

 tidal inlets 

 coostol structures 

 eolian processes 

 offshore transport 

 resource extraction 



subsurfoce fluid withdrawal 

 river basin development 

 maintenance dredging 

 beach maintenance 

 coastal structures 

 artificial passes 

 dune alterations 

 highway construction 



temperature 



evapotranspirotion 



precipitation 



wove climate 

 longshore currents 

 riverine discharge 

 valley aggradation, 

 or incision 

 tides 

 wind 

 storms 



tectonic subsidence 

 compoctionol subsidence 

 eustatic sea level changes 

 secular sea level changes 



Figure 3. Interaction of factors affecting land losses. Arrows point toward 

 the dependent variables: the number of arrows originating from or terminating 

 at a particular factor indicates the relative degree of independence or inter- 

 action. For example, human activities are independent of the other factors, 

 but they affect sediment budget, coastal processes, relative sea-level condi- 

 tions, and. perhaps, climate (Morton 1977). 



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