58 S. L. Dingman et al. 



damming flow until sufficient head builds up to dislodge them and cause 

 sudden catastrophic flooding downstream. There is considerable bank 

 erosion at such times, due to the thermal/mechanical action of the water 

 and the mechanical action of the ice masses. 



Loss of the winter snow cover proceeds from the Brooks Range 

 northward across the Foothills and Coastal Plain. As indicated on the 

 satellite view of the eastern portion of the Arctic Slope (Figure 2-12), the 

 major valleys of the Brooks Range are seen to be more or less snow-free. 

 But close inspection reveals that many of the gullies on the mountain- 

 sides are filled with snowdrifts that extend to the valley bottoms. In the 

 Foothills the ridges melt out first, leaving snow in the gullies. Meltwater 

 collects in the larger valleys, reducing albedos and accelerating melting 

 there. Thus the major rivers have developed, or are in the process of de- 

 veloping, continuous open-water streams and generally appear as dark 

 bands, probably because of flooded areas and because melting is further 

 advanced. Many lakes appear darker than their surroundings, also be- 

 cause of standing water on the ice. The larger rivers flood their deltas and 

 the sea ice, forming large overflow plumes. 



Attempts have been made to model the snowmelt runoff process on 

 the Coastal Plain for watersheds ranging in size from 3.8 km^ to 13,890 

 km^ (Carlson et al. 1974, Dingman, unpubl.). The models used have con- 

 sisted of a snowmelt generator driven by climatic input and a simple stor- 

 age model to transform snowmelt input to streamflow output. The basic 

 form of the storage model is: 



q. = KiS-So)" 



where q, - runoff during period t 

 K and n = storage parameters 



S, = snowmelt during period t 



So = the amount of melt that is absorbed into "dead" 

 storage (filling lakes, ponds, troughs and soil pores). 



Using a simple snowmelt model, Dingman (unpubl.) accounted for 

 melt due to absorption of shortwave radiation only. Hourly melt was 

 routed through the storage model to simulate measured runoff in 

 Esatkuat Creek near Barrow (drainage area = 3.8 km^). The parameters 

 K and n were estimated from examination of the measured runoff 

 hydrograph for the area. The value of n was taken as unity, so the stor- 

 age model was effectively a linear reservoir. When modification was 

 made to account for the irregular distribution of snow depths over the 

 watershed, the model appeared to be quite successful (Figure 2-13). 



Carlson et al. (1974) simulated snowmeh from three large Arctic 

 Slope rivers— the Putuligayuk (456 km^, the Kuparuk (9210 km^), and 



